A Survey on Security and Privacy Protocols for Cognitive Wireless Sensor Networks
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paper_title: Security in Cognitive Radio Networks: Threats and Mitigation

paper_content:

This paper describes a new class of attacks specific to cognitive radio networks. Wireless devices that can learn from their environment can also be taught things by malicious elements of their environment. By putting artificial intelligence in charge of wireless network devices, we are allowing unanticipated, emergent behavior, fitting a perhaps distorted or manipulated level of optimality. The state space for a cognitive radio is made up of a variety of learned beliefs and current sensor inputs. By manipulating radio sensor inputs, an adversary can affect the beliefs of a radio, and consequently its behavior. In this paper we focus primarily on PHY-layer issues, describing several classes of attacks and giving specific examples for dynamic spectrum access and adaptive radio scenarios. These attacks demonstrate the capabilities of an attacker who can manipulate the spectral environment when a radio is learning. The most powerful of which is a self-propagating AI virus that could interactively teach radios to become malicious. We then describe some approaches for mitigating the effectiveness of these attacks by instilling some level of "common sense" into radio systems, and requiring learned beliefs to expire and be relearned. Lastly we provide a road-map for extending these ideas to higher layers in the network stack.
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paper_title: Cognitive Wireless Sensor Networks: Emerging topics and recent challenges

paper_content:

Adding cognition to the existing Wireless Sensor Networks (WSNs), or using numerous tiny sensors, similar to the idea presented in WSNs, in a Cognitive Radio Network (CRN) bring about many benefits. In this paper, we present an overview of Cognitive Wireless Sensor Networks (CWSNs), and discuss the emerging topics and recent challenges in the area. We discuss the main advantages, and suggest possible remedies to overcome the challenges. CWSNs enable current WSNs to overcome the scarcity problem of spectrum which is shared with many other successful systems such as Wi-Fi and Bluetooth. It has been shown that the coexistence of such networks can significantly degrade a WSN's performance. In addition, cognitive technology could provide access not only to new spectrum, but also to spectrum with better propagation characteristics. Moreover, by the adaptive change of system parameters such as modulation type and constellation size, different data rates can be achieved which in turn can directly influence the power consumption and the network lifetime. Furthermore, sensor measurements obtained within the network can provide the needed diversity to cope with spectrum fading at the physical layer.
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paper_title: Securing wireless sensor networks: a survey

paper_content:

The significant advances of hardware manufacturing technology and the development of efficient software algorithms make technically and economically feasible a network composed of numerous, small, low-cost sensors using wireless communications, that is, a wireless sensor network. WSNs have attracted intensive interest from both academia and industry due to their wide application in civil and military scenarios. In hostile scenarios, it is very important to protect WSNs from malicious attacks. Due to various resource limitations and the salient features of a wireless sensor network, the security design for such networks is significantly challenging. In this article, we present a comprehensive survey of WSN security issues that were investigated by researchers in recent years and that shed light on future directions for WSN security.
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paper_title: Security in Cognitive Radio Networks: The Required Evolution in Approaches to Wireless Network Security

paper_content:

This paper discusses the topic of wireless security in cognitive radio networks, delineating the key challenges in this area. With the ever-increasing scarcity of spectrum, cognitive radios are expected to become an increasingly important part of the overall wireless networking landscape. However, there is an important technical area that has received little attention to date in the cognitive radio paradigm: wireless security. The cognitive radio paradigm introduces entirely new classes of security threats and challenges, and providing strong security may prove to be the most difficult aspect of making cognitive radio a long-term commercially-viable concept. This paper delineates the key challenges in providing security in cognitive networks, discusses the current security posture of the emerging IEEE 802.22 cognitive radio standard, and identifies potential vulnerabilities along with potential mitigation approaches.
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paper_title: Cognitive Radio Based Wireless Sensor Networks

paper_content:

In recent years, we have seen tremendous growth in the applications of wireless sensor networks (WSNs) operating in unlicensed spectrum bands. However, there is evidence that existing unlicensed spectrum is becoming overcrowded. On the other hand, with recent advances in cognitive radio (CR) technology, it is possible to apply the dynamic spectrum access (DSA) model in WSNs to get access to less congested spectrum, possibly with better propagation characteristics. In this paper we present a conceptual design of CR-based WSNs, identify the main advantages and challenges of using CR technology, and suggest possible remedies to overcome the challenges. As an illustration, we study the performance of CR-based WSN used for the automation and control applications in residential and commercial premises. Our simulation results compare the performance of a CR-based WSN with a standard ZigBee/802.15.4 WSN.
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paper_title: 14 Security in Wireless Sensor Networks

paper_content:

A wide-band RF signal power detecting element includes, on an insulating substrate (21), at least one thin-film resistor (22a) for absorbing the power of a signal to be measured and generating heat, first and second ground electrodes (27, 28) formed by thin-film conductors, a first thin-film connecting portion (24) for electrically connecting the first ground electrode (27) to the thin-film resistor (22a), a second thin-film connecting portion (25) for electrically connecting the second ground electrode (28) to the thin-film resistor (22a) and narrowing the gap between the first and second thin-film connecting portions (24, 25) toward the thin-film resistor (22a), and an input electrode (26) formed between the first and second ground electrodes (27, 28) and electrically connected to the thin-film resistor (22a).
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paper_title: Achieving Energy Efficiency and QoS for Low-Rate Applications with 802.11e

paper_content:

This paper analyses the energy efficiency and QoS performance of 802.11e as a connectivity solution for low-rate applications, such as wireless automation and monitoring. The authors consider non-interference and co-existence scenarios and show through modeling and simulations that the power save operation mode and the EDCA QoS mechanisms in the 802.11e standard can be exploited to achieve the power consumption requirements of low-rate applications. The authors also provide a comparison of the energy efficiency between 802.11e and 802.15.4 under varying interference and traffic conditions. Our results suggest that in some specific scenarios, 802.11e can achieve higher energy efficiency and QoS than 802.15.4.
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paper_title: Wireless Sensor Network Attacks and Security Mechanisms: A Short Survey

paper_content:

Wireless sensor networks are specific adhoc networks. They are characterized by their limited computing power and energy constraints. This paper proposes a study of security in this kind of network. We show what are the specificities and vulnerabilities of wireless sensor networks. We present a list of attacks, which can be found in these particular networks, and how they use their vulnerabilities. Finally we discuss about different solutions made by the scientific community to secure wireless sensor networks.
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paper_title: Denial of Service in Sensor Networks

paper_content:

Sensor networks hold the promise of facilitating large-scale, real-time data processing in complex environments, helping to protect and monitor military, environmental, safety-critical, or domestic infrastructures and resources, Denial-of-service attacks against such networks, however, may permit real world damage to public health and safety. Without proper security mechanisms, networks will be confined to limited, controlled environments, negating much of the promise they hold. The limited ability of individual sensor nodes to thwart failure or attack makes ensuring network availability more difficult. To identify denial-of-service vulnerabilities, the authors analyzed two effective sensor network protocols that did not initially consider security. These examples demonstrate that consideration of security at design time is the best way to ensure successful network deployment.
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paper_title: Secure routing in wireless sensor networks: attacks and countermeasures

paper_content:

We consider routing security in wireless sensor networks. Many sensor network routing protocols have been proposed, but none of them have been designed with security as a goal. We propose security goals for routing in sensor networks, show how attacks against ad-hoc and peer-to-peer networks can be adapted into powerful attacks against sensor networks, introduce two classes of novel attacks against sensor networks sinkholes and HELLO floods, and analyze the security of all the major sensor network routing protocols. We describe crippling attacks against all of them and suggest countermeasures and design considerations. This is the first such analysis of secure routing in sensor networks.
---
paper_title: Denial of Service in Sensor Networks

paper_content:

Sensor networks hold the promise of facilitating large-scale, real-time data processing in complex environments, helping to protect and monitor military, environmental, safety-critical, or domestic infrastructures and resources, Denial-of-service attacks against such networks, however, may permit real world damage to public health and safety. Without proper security mechanisms, networks will be confined to limited, controlled environments, negating much of the promise they hold. The limited ability of individual sensor nodes to thwart failure or attack makes ensuring network availability more difficult. To identify denial-of-service vulnerabilities, the authors analyzed two effective sensor network protocols that did not initially consider security. These examples demonstrate that consideration of security at design time is the best way to ensure successful network deployment.
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paper_title: An on-demand secure routing protocol resilient to byzantine failures

paper_content:

An ad hoc wireless network is an autonomous self-organizing system ofmobile nodes connected by wireless links where nodes not in directrange can communicate via intermediate nodes. A common technique usedin routing protocols for ad hoc wireless networks is to establish therouting paths on-demand, as opposed to continually maintaining acomplete routing table. A significant concern in routing is theability to function in the presence of byzantine failures whichinclude nodes that drop, modify, or mis-route packets in an attempt todisrupt the routing service.We propose an on-demand routing protocol for ad hoc wireless networks that provides resilience to byzantine failures caused by individual or colluding nodes. Our adaptive probing technique detects a malicious link after log n faults have occurred, where n is the length of the path. These links are then avoided by multiplicatively increasing their weights and by using an on-demand route discovery protocol that finds a least weight path to the destination.
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paper_title: Routing Security Issues in Wireless Sensor Networks: Attacks and Defenses

paper_content:

Wireless Sensor Networks (WSNs) are rapidly emerging as an important new area in wireless and mobile computing research. Applications of WSNs are numerous and growing, and range from indoor deployment scenarios in the home and office to outdoor deployment scenarios in adversary's territory in a tactical battleground (Akyildiz et al., 2002). For military environment, dispersal of WSNs into an adversary's territory enables the detection and tracking of enemy soldiers and vehicles. For home/office environments, indoor sensor networks offer the ability to monitor the health of the elderly and to detect intruders via a wireless home security system. In each of these scenarios, lives and livelihoods may depend on the timeliness and correctness of the sensor data obtained from dispersed sensor nodes. As a result, such WSNs must be secured to prevent an intruder from obstructing the delivery of correct sensor data and from forging sensor data. To address the latter problem, end-to-end data integrity checksums and post-processing of senor data can be used to identify forged sensor data (Estrin et al., 1999; Hu et al., 2003a; Ye et al., 2004). The focus of this chapter is on routing security in WSNs. Most of the currently existing routing protocols for WSNs make an optimization on the limited capabilities of the nodes and the application-specific nature of the network, but do not any the security aspects of the protocols. Although these protocols have not been designed with security as a goal, it is extremely important to analyze their security properties. When the defender has the liabilities of insecure wireless communication, limited node capabilities, and possible insider threats, and the adversaries can use powerful laptops with high energy and long range communication to attack the network, designing a secure routing protocol for WSNs is obviously a non-trivial task.
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paper_title: Denial of Service in Sensor Networks

paper_content:

Sensor networks hold the promise of facilitating large-scale, real-time data processing in complex environments, helping to protect and monitor military, environmental, safety-critical, or domestic infrastructures and resources, Denial-of-service attacks against such networks, however, may permit real world damage to public health and safety. Without proper security mechanisms, networks will be confined to limited, controlled environments, negating much of the promise they hold. The limited ability of individual sensor nodes to thwart failure or attack makes ensuring network availability more difficult. To identify denial-of-service vulnerabilities, the authors analyzed two effective sensor network protocols that did not initially consider security. These examples demonstrate that consideration of security at design time is the best way to ensure successful network deployment.
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paper_title: Distributed detection of node replication attacks in sensor networks

paper_content:

The low-cost, off-the-shelf hardware components in unshielded sensor-network nodes leave them vulnerable to compromise. With little effort, an adversary may capture nodes, analyze and replicate them, and surreptitiously insert these replicas at strategic locations within the network. Such attacks may have severe consequences; they may allow the adversary to corrupt network data or even disconnect significant parts of the network. Previous node replication detection schemes depend primarily on centralized mechanisms with single points of failure, or on neighborhood voting protocols that fail to detect distributed replications. To address these fundamental limitations, we propose two new algorithms based on emergent properties (Gligor (2004)), i.e., properties that arise only through the collective action of multiple nodes. Randomized multicast distributes node location information to randomly-selected witnesses, exploiting the birthday paradox to detect replicated nodes, while line-selected multicast uses the topology of the network to detect replication. Both algorithms provide globally-aware, distributed node-replica detection, and line-selected multicast displays particularly strong performance characteristics. We show that emergent algorithms represent a promising new approach to sensor network security; moreover, our results naturally extend to other classes of networks in which nodes can be captured, replicated and re-inserted by an adversary.
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paper_title: Source-location privacy in energy-constrained sensor network routing

paper_content:

As sensor-driven applications become increasingly integrated into our lives, issues related to sensor privacy will become increasingly important. Although many privacy-related issues can be addressed by security mechanisms, one sensor network privacy issue that cannot be adequately addressed by network security is confidentiality of the source sensor's location. In this paper, we focus on protecting the source's location by introducing suitable modifications to sensor routing protocols to make it difficult for an adversary to backtrack to the origin of the sensor communication. In particular, we focus on the class of flooding protocols. While developing and evaluating our privacy-aware routing protocols, we jointly consider issues of location-privacy as well as the amount of energy consumed by the sensor network. Motivated by the observations, we propose a flexible routing strategy, known as phantom routing, which protects the source's location. Phantom routing is a two-stage routing scheme that first consists of a directed walk along a random direction, followed by routing from the phantom source to the sink. Our investigations have shown that phantom routing is a powerful technique for protecting the location of the source during sensor transmissions.
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paper_title: Energy Analysis of Public-Key Cryptography for Wireless Sensor Networks

paper_content:

In this paper, we quantify the energy cost of authentication and key exchange based on public-key cryptography on an 8-bit microcontroller platform. We present a comparison of two public-key algorithms, RSA and elliptic curve cryptography (ECC), and consider mutual authentication and key exchange between two untrusted parties such as two nodes in a wireless sensor network. Our measurements on an Atmel ATmega128L low-power microcontroller indicate that public-key cryptography is very viable on 8-bit energy-constrained platforms even if implemented in software. We found ECC to have a significant advantage over RSA as it reduces computation time and also the amount of data transmitted and stored.
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paper_title: DIGITALIZED SIGNATURES AND PUBLIC-KEY FUNCTIONS AS INTRACTABLE AS FACTORIZATION

paper_content:

We introduce a new class of public-key functions involving a number n = pq having two large prime factors. As usual, the key n is public, while p and q are the private key used by the issuer for production of signatures and function inversion. These functions can be used for all the applications involving public-key functions proposed by Diffie and Hellman, including digitalized signatures. We prove that for any given n, if we can invert the function y = E (x1) for even a small percentage of the values y then we can factor n. Thus, as long as factorization of large numbers remains practically intractable, for appropriate chosen keys not even a small percentage of signatures are forgeable. Breaking the RSA function is at most hard as factorization, but is not known to be equivalent to factorization even in the weak sense that ability to invert all function values entails ability to factor the key. Computation time for these functions, i.e. signature verification, is several hundred times faster than for the RSA scheme. Inversion time, using the private key, is comparable. The almost-everywhere intractability of signature-forgery for our functions (on the assumption that factoring is intractable) is of great practical significance and seems to be the first proved result of this kind.
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paper_title: Public key cryptography in sensor networks - revisited

paper_content:

The common perception of public key cryptography is that it is complex, slow and power hungry, and as such not at all suitable for use in ultra-low power environments like wireless sensor networks. It is therefore common practice to emulate the asymmetry of traditional public key based cryptographic services through a set of protocols [1] using symmetric key based message authentication codes (MACs). Although the low computational complexity of MACs is advantageous, the protocol layer requires time synchronization between devices on the network and a significant amount of overhead for communication and temporary storage. The requirement for a general purpose CPU to implement these protocols as well as their complexity makes them prone to vulnerabilities and practically eliminates all the advantages of using symmetric key techniques in the first place. In this paper we challenge the basic assumptions about public key cryptography in sensor networks which are based on a traditional software based approach. We propose a custom hardware assisted approach for which we claim that it makes public key cryptography feasible in such environments, provided we use the right selection of algorithms and associated parameters, careful optimization, and low-power design techniques. In order to validate our claim we present proof of concept implementations of two different algorithms—Rabin’s Scheme and NtruEncrypt—and analyze their architecture and performance according to various established metrics like power consumption, area, delay, throughput, level of security and energy per bit. Our implementation of NtruEncrypt in ASIC standard cell logic uses no more than 3,000 gates with an average power consumption of less than 20 μW. We envision that our public key core would be embedded into a light-weight sensor node architecture.
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paper_title: A public-key infrastructure for key distribution in TinyOS based on elliptic curve cryptography

paper_content:

We present the first known implementation of elliptic curve cryptography over F/sub 2p/ for sensor networks based on the 8-bit, 7.3828-MHz MICA2 mote. Through instrumentation of UC Berkeley's TinySec module, we argue that, although secret-key cryptography has been tractable in this domain for some time, there has remained a need for an efficient, secure mechanism for distribution of secret keys among nodes. Although public-key infrastructure has been thought impractical, we argue, through analysis of our own implementation for TinyOS of multiplication of points on elliptic curves, that public-key infrastructure is, in fact, viable for TinySec keys' distribution, even on the MICA2. We demonstrate that public keys can be generated within 34 seconds, and that shared secrets can be distributed among nodes in a sensor network within the same, using just over 1 kilobyte of SRAM and 34 kilobytes of ROM.
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paper_title: Pgp in constrained wireless devices

paper_content:

The market for Personal Digital Assistants (PDAs) is growing at a rapid pace. An increasing number of products, such as the PalmPilot, are adding wireless communications capabilities. PDA users are now able to send and receive email just as they would from their networked desktop machines. Because of the inherent insecurity of wireless environments, a system is needed for secure email communications. The requirements for the security system will likely be influenced by the constraints of the PDA, including limited memory, limited processing power, limited bandwidth, and a limited user interface. ::: ::: This paper describes our experience with porting PGP to the Research in Motion (RIM) two-way pager, and incorporating elliptic curve cryptography into PGP's suite of public-key ciphers. Our main conclusion is that PGP is a viable solution for providing secure and interoperable email communications between constrained wireless devices and desktop machines.
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paper_title: Comparing Elliptic Curve Cryptography and RSA on 8-bit CPUs

paper_content:

Strong public-key cryptography is often considered to be too computationally expensive for small devices if not accelerated by cryptographic hardware. We revisited this statement and implemented elliptic curve point multiplication for 160-bit, 192-bit, and 224-bit NIST/SECG curves over GF(p) and RSA-1024 and RSA-2048 on two 8-bit microcontrollers. To accelerate multiple-precision multiplication, we propose a new algorithm to reduce the number of memory accesses.
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paper_title: The RC5 Encryption Algorithm

paper_content:

This document describes the RC5 encryption algorithm, a fast symmetric block cipher suitable for hardware or software implementations. A novel feature of RC5 is the heavy use of data-dependent rotations. RC5 has a variable word size, a variable number of rounds, and a variable-length secret key. The encryption and decryption algorithms are exceptionally simple.
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paper_title: Handbook of Applied Cryptography

paper_content:

From the Publisher: ::: A valuable reference for the novice as well as for the expert who needs a wider scope of coverage within the area of cryptography, this book provides easy and rapid access of information and includes more than 200 algorithms and protocols; more than 200 tables and figures; more than 1,000 numbered definitions, facts, examples, notes, and remarks; and over 1,250 significant references, including brief comments on each paper.
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paper_title: The MD5 Message-Digest Algorithm

paper_content:

This document describes the MD5 message-digest algorithm. The ::: algorithm takes as input a message of arbitrary length and produces as ::: output a 128-bit "fingerprint" or "message digest" of the input. This ::: memo provides information for the Internet community. It does not ::: specify an Internet standard.
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paper_title: Denial of Service in Sensor Networks

paper_content:

Sensor networks hold the promise of facilitating large-scale, real-time data processing in complex environments, helping to protect and monitor military, environmental, safety-critical, or domestic infrastructures and resources, Denial-of-service attacks against such networks, however, may permit real world damage to public health and safety. Without proper security mechanisms, networks will be confined to limited, controlled environments, negating much of the promise they hold. The limited ability of individual sensor nodes to thwart failure or attack makes ensuring network availability more difficult. To identify denial-of-service vulnerabilities, the authors analyzed two effective sensor network protocols that did not initially consider security. These examples demonstrate that consideration of security at design time is the best way to ensure successful network deployment.
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paper_title: Secure Routing for Mobile Ad Hoc Networks

paper_content:

Buttyan found out a security flaw in Ariadne (Y.C. Hu, A. Perrig, andD. B. Johnson, "Ariadne: a secure on-demand routing protocol for ad hoc networks," in Proc. of the Eighth ACM hitl Conf. on Mobile Computing and Networking (MOBI.COM 2002), pp.23-28. Atlanta, GA.2002.) and proposed a secure routing protocol, EndairA (L. Buttyan, and I. Vajda, "Towards provable security for ad hoc routing protocols", in Proc. of the 2nd ACM Workshop on Security of ad hoc and Sensor Networks, 2005 and G. Acs, L. Buttyan, and I. Vajda, "Provably secure on-demand source routing in mobile ad hoc networks," IEEE Transactions on Mobile Computing, Vol. 5, No. 11, November 2006.), with the ability to resist active-1-1 attacks. But unfortunately we discover an as yet unknown active-0- 1 attack which we call man-in-the-middle attack and EndairA couldn 't resist. Accordingly we propose a new secure routing protocol, EndairALoc. Analysis shows that EndairALoc can resist not only active-1-1 attacks but also the wormhole attack. Furthermore EndairALoc uses pairwise secret keys instead of public keys used in EndairA. Compared with EndairA, EndairALoc can save more energy in the routing establishment.
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paper_title: Efficient Distribution of Key Chain Commitments for Broadcast Authentication in Distributed Sensor Networks

paper_content:

Broadcast authentication is a fundamental security service in distributed sensor networks. A scheme named $\mu$TESLA has been proposed for efficient broadcast authentication in such networks. However, $\mu$TESLA requires initial distribution of certain information based on unicast between the base station and each sensor node before the actual authentication of broadcast messages. Due to the limited bandwidth in wireless sensor networks, this initial unicast-based distribution severely limits the application of $\mu$TESLA in large sensor networks. This paper presents a novel technique to replace the unicast-based initialization with a broadcast-based one. As a result, $\mu$TESLA can be used in a sensor network with a large amount of sensors, as long as the message from the base station can reach these sensor nodes. This paper further explores several techniques that improve the performance, the robustness, as well as the security of the proposed method. The resulting protocol satisfies several nice properties, including low overhead, tolerance of message loss, scalability to large networks, and resistance to replay attacks as well as some known Denial of Service (DOS) attacks.
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paper_title: INSENS: Intrusion-Tolerant Routing in Wireless Sensor Networks

paper_content:

This paper describes an INtrusion-tolerant routing protocol for wireless SEnsor NetworkS (INSENS). INSENS securely and efficiently constructs tree-structured routing for wireless sensor networks (WSNs). The key objective of an INSENS network is to tolerate damage caused by an intruder who has compromised deployed sensor nodes and is intent on injecting, modifying, or blocking packets. To limit or localize the damage caused by such an intruder, INSENS incorporates distributed lightweight security mechanisms, including efficient one-way hash chains and nested keyed message authentication codes that defend against wormhole attacks, as well as multipath routing. Adapting to WSN characteristics, the design of INSENS also pushes complexity away from resource-poor sensor nodes towards resource-rich base stations. An enhanced single-phase version of INSENS scales to large networks, integrates bidirectional verification to defend against rushing attacks, accommodates multipath routing to multiple base stations, enables secure joining/leaving, and incorporates a novel pairwise key setup scheme based on transitory global keys that is more resilient than LEAP. Simulation results are presented to demonstrate and assess the tolerance of INSENS to various attacks launched by an adversary. A prototype implementation of INSENS over a network of MICA2 motes is presented to evaluate the cost incurred.
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paper_title: Energy Analysis of Public-Key Cryptography for Wireless Sensor Networks

paper_content:

In this paper, we quantify the energy cost of authentication and key exchange based on public-key cryptography on an 8-bit microcontroller platform. We present a comparison of two public-key algorithms, RSA and elliptic curve cryptography (ECC), and consider mutual authentication and key exchange between two untrusted parties such as two nodes in a wireless sensor network. Our measurements on an Atmel ATmega128L low-power microcontroller indicate that public-key cryptography is very viable on 8-bit energy-constrained platforms even if implemented in software. We found ECC to have a significant advantage over RSA as it reduces computation time and also the amount of data transmitted and stored.
---
paper_title: Secure routing in wireless sensor networks: attacks and countermeasures

paper_content:

We consider routing security in wireless sensor networks. Many sensor network routing protocols have been proposed, but none of them have been designed with security as a goal. We propose security goals for routing in sensor networks, show how attacks against ad-hoc and peer-to-peer networks can be adapted into powerful attacks against sensor networks, introduce two classes of novel attacks against sensor networks sinkholes and HELLO floods, and analyze the security of all the major sensor network routing protocols. We describe crippling attacks against all of them and suggest countermeasures and design considerations. This is the first such analysis of secure routing in sensor networks.
---
paper_title: Public key cryptography in sensor networks - revisited

paper_content:

The common perception of public key cryptography is that it is complex, slow and power hungry, and as such not at all suitable for use in ultra-low power environments like wireless sensor networks. It is therefore common practice to emulate the asymmetry of traditional public key based cryptographic services through a set of protocols [1] using symmetric key based message authentication codes (MACs). Although the low computational complexity of MACs is advantageous, the protocol layer requires time synchronization between devices on the network and a significant amount of overhead for communication and temporary storage. The requirement for a general purpose CPU to implement these protocols as well as their complexity makes them prone to vulnerabilities and practically eliminates all the advantages of using symmetric key techniques in the first place. In this paper we challenge the basic assumptions about public key cryptography in sensor networks which are based on a traditional software based approach. We propose a custom hardware assisted approach for which we claim that it makes public key cryptography feasible in such environments, provided we use the right selection of algorithms and associated parameters, careful optimization, and low-power design techniques. In order to validate our claim we present proof of concept implementations of two different algorithms—Rabin’s Scheme and NtruEncrypt—and analyze their architecture and performance according to various established metrics like power consumption, area, delay, throughput, level of security and energy per bit. Our implementation of NtruEncrypt in ASIC standard cell logic uses no more than 3,000 gates with an average power consumption of less than 20 μW. We envision that our public key core would be embedded into a light-weight sensor node architecture.
---
paper_title: Comparing Elliptic Curve Cryptography and RSA on 8-bit CPUs

paper_content:

Strong public-key cryptography is often considered to be too computationally expensive for small devices if not accelerated by cryptographic hardware. We revisited this statement and implemented elliptic curve point multiplication for 160-bit, 192-bit, and 224-bit NIST/SECG curves over GF(p) and RSA-1024 and RSA-2048 on two 8-bit microcontrollers. To accelerate multiple-precision multiplication, we propose a new algorithm to reduce the number of memory accesses.
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paper_title: A distributed protocol for detection of packet dropping attack in mobile ad hoc networks

paper_content:

In multi-hop mobile ad hoc networks (MANETs), mobile nodes cooperate with each other without using any infrastructure such as access points or base stations. Security remains a major challenge for these networks due to their features of open medium, dynamically changing topologies, reliance on cooperative algorithms, absence of centralized monitoring points, and lack of clear lines of defense. Among the various attacks to which MANETs are vulnerable, malicious packet dropping attack is very common where a malicious node can partially degrade or completely disrupt communication in the network by consistently dropping packets. In this paper, a mechanism for detection of packet dropping attack is presented based on cooperative participation of the nodes in a MANET. The redundancy of routing information in an ad hoc network is utilized to make the scheme robust so that it works effectively even in presence of transient network partitioning and Byzantine failure of nodes. The proposed scheme is fully cooperative and thus more secure as the vulnerabilities of any election algorithm used for choosing a subset of nodes for cooperation are absent. Simulation results show the effectiveness of the protocol.
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paper_title: Multilevel μTESLA: Broadcast authentication for distributed sensor networks

paper_content:

Broadcast authentication is a fundamental security service in distributed sensor networks. This paper presents the development of a scalable broadcast authentication scheme named multilevel μTESLA based on μTESLA, a broadcast authentication protocol whose scalability is limited by its unicast-based initial parameter distribution. Multilevel μTESLA satisfies several nice properties, including low overhead, tolerance of message loss, scalability to large networks, and resistance to replay attacks as well as denial-of-service attacks. This paper also presents the experimental results obtained through simulation, which demonstrate the performance of the proposed scheme under severe denial-of-service attacks and poor channel quality.
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paper_title: An efficient scheme for authenticating public keys in sensor networks

paper_content:

With the advance of technology, Public Key Cryptography (PKC) will sooner or later be widely used in wireless sensor networks. Recently, it has been shown that the performance of some public-key algorithms, such as Elliptic Curve Cryptography (ECC), is already close to being practical on sensor nodes. However, the energy consumption of PKC is still expensive, especially compared to symmetric-key algorithms. To maximize the lifetime of batteries, we should minimize the use of PKC whenever possible in sensor networks.This paper investigates how to replace one of the important PKC operations--the public key authentication--with symmetric key operations that are much more efficient. Public key authentication is to verify the authenticity of another party's public key to make sure that the public key is really owned by the person it is claimed to belong to. In PKC, this operation involves an expensive signature verification on a certificate. We propose an efficient alternative that uses one-way hash function only. Our scheme uses all sensor's public keys to construct a forest of Merkle trees of different heights. By optimally selecting the height of each tree, we can minimize the computation and communication costs. The performance of our scheme is evaluated in the paper.
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paper_title: Guide to Elliptic Curve Cryptography

paper_content:

Elliptic curves also figured prominently in the recent proof of Fermat's Last Theorem by Andrew Wiles. Originally pursued for purely aesthetic reasons, elliptic curves have recently been utilized in devising algorithms for factoring integers, primality proving, and in public-key cryptography. In this article, we aim to give the reader an introduction to elliptic curve cryptosystems, and to demonstrate why these systems provide relatively small block sizes, high-speed software and hardware implementations, and offer the highest strength-per-key-bit of any known public-key scheme.
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paper_title: LKHW: a directed diffusion-based secure multicast scheme for wireless sensor networks

paper_content:

In this paper, we present a mechanism for securing group communications in Wireless Sensor Networks (WSN). First, we derive an extension of logical key hierarchy (LKH). Then we merge the extension with directed diffusion. The resulting protocol, LKHW, combines the advantages of both LKH and directed diffusion: robustness in routing, and security from the tried and tested concepts of secure multicast. In particular, LKHW enforces both backward and forward secrecy, while incurring an energy cost that scales roughly logarithmically with the group size. This is the first security protocol that leverages directed diffusion, and we show how directed diffusion can be extended to incorporate security in an efficient manner.
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paper_title: SPINS: security protocols for sensor networks

paper_content:

Wireless sensor networks will be widely deployed in the near future. While much research has focused on making these networks feasible and useful, security has received little attention. We present a suite of security protocols optimized for sensor networks: SPINS. SPINS has two secure building blocks: SNEP and μTESLA. SNEP includes: data confidentiality, two-party data authentication, and evidence of data freshness. μTESLA provides authenticated broadcast for severely resource-constrained environments. We implemented the above protocols, and show that they are practical even on minimal hardware: the performance of the protocol suite easily matches the data rate of our network. Additionally, we demonstrate that the suite can be used for building higher level protocols.
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paper_title: LEAP+: Efficient security mechanisms for large-scale distributed sensor networks

paper_content:

We describe LEAPp (Localized Encryption and Authentication Protocol), a key management protocol for sensor networks that is designed to support in-network processing, while at the same time restricting the security impact of a node compromise to the immediate network neighborhood of the compromised node. The design of the protocol is motivated by the observation that different types of messages exchanged between sensor nodes have different security requirements, and that a single keying mechanism is not suitable for meeting these different security requirements. LEAPp supports the establishment of four types of keys for each sensor node: an individual key shared with the base station, a pairwise key shared with another sensor node, a cluster key shared with multiple neighboring nodes, and a global key shared by all the nodes in the network. LEAPp also supports (weak) local source authentication without precluding in-network processing. Our performance analysis shows that LEAPp is very efficient in terms of computational, communication, and storage costs. We analyze the security of LEAPp under various attack models and show that LEAPp is very effective in defending against many sophisticated attacks, such as HELLO flood attacks, node cloning attacks, and wormhole attacks. A prototype implementation of LEAPp on a sensor network testbed is also described.
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paper_title: Directed diffusion: a scalable and robust communication paradigm for sensor networks

paper_content:

Advances in processor, memory and radio technology will enable small and cheap nodes capable of sensing, communication and computation. Networks of such nodes can coordinate to perform distributed sensing of environmental phenomena. In this paper, we explore the directed diffusion paradigm for such coordination. Directed diffusion is datacentric in that all communication is for named data. All nodes in a directed diffusion-based network are application-aware. This enables diffusion to achieve energy savings by selecting empirically good paths and by caching and processing data in-network. We explore and evaluate the use of directed diffusion for a simple remote-surveillance sensor network.
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paper_title: Routing Security Issues in Wireless Sensor Networks: Attacks and Defenses

paper_content:

Wireless Sensor Networks (WSNs) are rapidly emerging as an important new area in wireless and mobile computing research. Applications of WSNs are numerous and growing, and range from indoor deployment scenarios in the home and office to outdoor deployment scenarios in adversary's territory in a tactical battleground (Akyildiz et al., 2002). For military environment, dispersal of WSNs into an adversary's territory enables the detection and tracking of enemy soldiers and vehicles. For home/office environments, indoor sensor networks offer the ability to monitor the health of the elderly and to detect intruders via a wireless home security system. In each of these scenarios, lives and livelihoods may depend on the timeliness and correctness of the sensor data obtained from dispersed sensor nodes. As a result, such WSNs must be secured to prevent an intruder from obstructing the delivery of correct sensor data and from forging sensor data. To address the latter problem, end-to-end data integrity checksums and post-processing of senor data can be used to identify forged sensor data (Estrin et al., 1999; Hu et al., 2003a; Ye et al., 2004). The focus of this chapter is on routing security in WSNs. Most of the currently existing routing protocols for WSNs make an optimization on the limited capabilities of the nodes and the application-specific nature of the network, but do not any the security aspects of the protocols. Although these protocols have not been designed with security as a goal, it is extremely important to analyze their security properties. When the defender has the liabilities of insecure wireless communication, limited node capabilities, and possible insider threats, and the adversaries can use powerful laptops with high energy and long range communication to attack the network, designing a secure routing protocol for WSNs is obviously a non-trivial task.
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paper_title: Denial of Service in Sensor Networks

paper_content:

Sensor networks hold the promise of facilitating large-scale, real-time data processing in complex environments, helping to protect and monitor military, environmental, safety-critical, or domestic infrastructures and resources, Denial-of-service attacks against such networks, however, may permit real world damage to public health and safety. Without proper security mechanisms, networks will be confined to limited, controlled environments, negating much of the promise they hold. The limited ability of individual sensor nodes to thwart failure or attack makes ensuring network availability more difficult. To identify denial-of-service vulnerabilities, the authors analyzed two effective sensor network protocols that did not initially consider security. These examples demonstrate that consideration of security at design time is the best way to ensure successful network deployment.
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paper_title: DOS-Resistant Authentication with Client Puzzles

paper_content:

Denial of service by server resource exhaustion has become a major security threat in open communications networks. Public-key authentication does not completely protect against the attacks because the authentication protocols often leave ways for an unauthenticated client to consume a server's memory space and computational resources by initiating a large number of protocol runs and inducing the server to perform expensive cryptographic computations. We show how stateless authentication protocols and the client puzzles of Juels and Brainard can be used to prevent such attacks.
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paper_title: A pairwise key predistribution scheme for wireless sensor networks

paper_content:

To achieve security in wireless sensor networks, it is important to be able to encrypt and authenticate messages sent between sensor nodes. Before doing so, keys for performing encryption and authentication must be agreed upon by the communicating parties. Due to resource constraints, however, achieving key agreement in wireless sensor networks is nontrivial. Many key agreement schemes used in general networks, such as Diffie-Hellman and other public-key based schemes, are not suitable for wireless sensor networks due to the limited computational abilities of the sensor nodes. Predistribution of secret keys for all pairs of nodes is not viable due to the large amount of memory this requires when the network size is large.In this paper, we provide a framework in which to study the security of key predistribution schemes, propose a new key predistribution scheme which substantially improves the resilience of the network compared to previous schemes, and give an in-depth analysis of our scheme in terms of network resilience and associated overhead. Our scheme exhibits a nice threshold property: when the number of compromised nodes is less than the threshold, the probability that communications between any additional nodes are compromised is close to zero. This desirable property lowers the initial payoff of smaller-scale network breaches to an adversary, and makes it necessary for the adversary to attack a large fraction of the network before it can achieve any significant gain.
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paper_title: A key-management scheme for distributed sensor networks

paper_content:

Distributed Sensor Networks (DSNs) are ad-hoc mobile networks that include sensor nodes with limited computation and communication capabilities. DSNs are dynamic in the sense that they allow addition and deletion of sensor nodes after deployment to grow the network or replace failing and unreliable nodes. DSNs may be deployed in hostile areas where communication is monitored and nodes are subject to capture and surreptitious use by an adversary. Hence DSNs require cryptographic protection of communications, sensor-capture detection, key revocation and sensor disabling. In this paper, we present a key-management scheme designed to satisfy both operational and security requirements of DSNs. The scheme includes selective distribution and revocation of keys to sensor nodes as well as node re-keying without substantial computation and communication capabilities. It relies on probabilistic key sharing among the nodes of a random graph and uses simple protocols for shared-key discovery and path-key establishment, and for key revocation, re-keying, and incremental addition of nodes. The security and network connectivity characteristics supported by the key-management scheme are discussed and simulation experiments presented.
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paper_title: Distributed detection of node replication attacks in sensor networks

paper_content:

The low-cost, off-the-shelf hardware components in unshielded sensor-network nodes leave them vulnerable to compromise. With little effort, an adversary may capture nodes, analyze and replicate them, and surreptitiously insert these replicas at strategic locations within the network. Such attacks may have severe consequences; they may allow the adversary to corrupt network data or even disconnect significant parts of the network. Previous node replication detection schemes depend primarily on centralized mechanisms with single points of failure, or on neighborhood voting protocols that fail to detect distributed replications. To address these fundamental limitations, we propose two new algorithms based on emergent properties (Gligor (2004)), i.e., properties that arise only through the collective action of multiple nodes. Randomized multicast distributes node location information to randomly-selected witnesses, exploiting the birthday paradox to detect replicated nodes, while line-selected multicast uses the topology of the network to detect replication. Both algorithms provide globally-aware, distributed node-replica detection, and line-selected multicast displays particularly strong performance characteristics. We show that emergent algorithms represent a promising new approach to sensor network security; moreover, our results naturally extend to other classes of networks in which nodes can be captured, replicated and re-inserted by an adversary.
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paper_title: Protecting Access to People Location Information

paper_content:

Ubiquitous computing provides new types of information for which access needs to be controlled. For instance, a person’s current location is a sensitive piece of information, and only authorized entities should be able to learn it. We present several challenges that arise for the specification and implementation of policies controlling access to location information. For example, there can be multiple sources of location information, policies need to be flexible, conflicts between policies might occur, and privacy issues need to be taken into account. Different environments handle these challenges in a different way. We discuss the challenges in the context of a hospital and a university environment. We show how our design of an access control mechanism for a system providing people location information addresses the challenges. Our mechanism can be deployed in different environments. We demonstrate feasibility of our design with an example implementation based on digital certificates.
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paper_title: Framework for security and privacy in automotive telematics

paper_content:

Automotive telematics may be defined as the information-intensive applications that are being enabled for vehicles by a combination of telecommunications and computing technology. Telematics by its nature requires the capture of sensor data, storage and exchange of data to obtain remote services. In order for automotive telematics to grow to its full potential, telematics data must be protected. Data protection must include privacy and security for end-users, service providers and application providers. In this paper, we propose a new framework for data protection that is built on the foundation of privacy and security technologies. The privacy technology enables users and service providers to define flexible data model and policy models. The security technology provides traditional capabilities such as encryption, authentication, non-repudiation. In addition, it provides secure environments for protected execution, which is essential to limiting data access to specific purposes.
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paper_title: Preserving Source-Location Privacy in Wireless Sensor Networks

paper_content:

Wireless sensor networks (WSN) have the potential to be widely used in many areas for unattended event monitoring. Mainly due to lack of a protected physical boundary, wireless communications are vulnerable to unauthorized interception and detection. Privacy is becoming one of the major issues that jeopardize the successful deployment of wireless sensor networks. While confidentiality of the message can be ensured through content encryption, it is much more difficult to adequately address the source-location privacy. For WSN, source-location privacy service is further complicated by the fact that the sensor nodes consist of low-cost and low-power radio devices, computationally intensive cryptographic algorithms (such as public-key cryptosystems) and large scale broadcasting-based protocols are not suitable for WSN. In this paper, we propose a scheme to provide both content confidentiality and source-location privacy through routing to a randomly selected intermediate node (RRIN) and a network mixing ring (NMR), where the RRIN provides local source-location privacy and NMR yields network-level (global) source-location privacy. While being able to provide source-location privacy for WSN, our simulation results also demonstrate that the proposed scheme is very efficient and can be used for practical applications.
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paper_title: Source-location privacy in energy-constrained sensor network routing

paper_content:

As sensor-driven applications become increasingly integrated into our lives, issues related to sensor privacy will become increasingly important. Although many privacy-related issues can be addressed by security mechanisms, one sensor network privacy issue that cannot be adequately addressed by network security is confidentiality of the source sensor's location. In this paper, we focus on protecting the source's location by introducing suitable modifications to sensor routing protocols to make it difficult for an adversary to backtrack to the origin of the sensor communication. In particular, we focus on the class of flooding protocols. While developing and evaluating our privacy-aware routing protocols, we jointly consider issues of location-privacy as well as the amount of energy consumed by the sensor network. Motivated by the observations, we propose a flexible routing strategy, known as phantom routing, which protects the source's location. Phantom routing is a two-stage routing scheme that first consists of a directed walk along a random direction, followed by routing from the phantom source to the sink. Our investigations have shown that phantom routing is a powerful technique for protecting the location of the source during sensor transmissions.
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paper_title: How to leak a secret

paper_content:

In this paper we formalize the notion of a ring signature, which makes it possible to specify a set of possible signers without revealing which member actually produced the signature. Unlike group signatures, ring signatures have no group managers, no setup procedures, no revocation procedures, and no coordination: any user can choose any set of possible signers that includes himself, and sign any message by using his secret key and the others' public keys, without getting their approval or assistance. Ring signatures provide an elegant way to leak authoritative secrets in an anonymous way, to sign casual email in a way which can only be verified by its intended recipient, and to solve other problems in multiparty computations. The main contribution of this paper is a new construction of such signatures which is unconditionally signer-ambiguous, provably secure in the random oracle model, and exceptionally efficient: adding each ring member increases the cost of signing or verifying by a single modular multiplication and a single symmetric encryption.
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paper_title: Privacy and security in library RFID: issues, practices, and architectures

paper_content:

We expose privacy issues related to Radio Frequency Identification (RFID) in libraries, describe current deployments, and suggest novel architectures for library RFID. Libraries are a fast growing application of RFID; the technology promises to relieve repetitive strain injury, speed patron self-checkout, and make possible comprehensive inventory. Unlike supply-chain RFID, library RFID requires item-level tagging, thereby raising immediate patron privacy issues. Current conventional wisdom suggests that privacy risks are negligible unless an adversary has access to library databases. We show this is not the case. In addition, we identify private authentication as a key technical issue: how can a reader and tag that share a secret efficiently authenticate each other without revealing their identities to an adversary? Previous solutions to this problem require reader work linear in the number of tags. We give a general scheme for building private authentication with work logarithmic in the number of tags, given a scheme with linear work as a sub protocol. This scheme may be of independent interest beyond RFID applications. We also give a simple scheme that provides security against a passive eavesdropper using XOR alone, without pseudo-random functions or other heavy crypto operations.
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paper_title: Preserving source location privacy in monitoring-based wireless sensor networks

paper_content:

While a wireless sensor network is deployed to monitor certain events and pinpoint their locations, the location information is intended only for legitimate users. However, an eavesdropper can monitor the traffic and deduce the approximate location of monitored objects in certain situations. We first describe a successful attack against the flooding-based phantom routing, proposed in the seminal work by Celal Ozturk, Yanyong Zhang, and Wade Trappe. Then, we propose GROW (Greedy Random Walk), a two-way random walk, i.e., from both source and sink, to reduce the chance an eavesdropper can collect the location information. We improve the delivery rate by using local broadcasting and greedy forwarding. Privacy protection is verified under a backtracking attack model. The message delivery time is a little longer than that of the broadcasting-based approach, but it is still acceptable if we consider the enhanced privacy preserving capability of this new approach. At the same time, the energy consumption is less than half the energy consumption of flooding-base phantom routing, which is preferred in a low duty cycle, environmental monitoring sensor network.
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paper_title: Resilient aggregation in sensor networks

paper_content:

This paper studies security for data aggregation in sensor networks. Current aggregation schemes were designed without security in mind and there are easy attacks against them. We examine several approaches for making these aggregation schemes more resilient against certain attacks, and we propose a mathematical framework for formally evaluating their security.
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paper_title: A Survey on the Encryption of Convergecast Traffic with In-Network Processing

paper_content:

We present an overview of end-to-end encryption solutions for convergecast traffic in wireless sensor networks that support in-network processing at forwarding intermediate nodes. Other than hop-by-hop based encryption approaches, aggregator nodes can perform in-network processing on encrypted data. Since it is not required to decrypt the incoming ciphers before aggregating, substantial advantages are 1) neither keys nor plaintext is available at aggregating nodes, 2) the overall energy consumption of the backbone can be reduced, 3) the system is more flexible with respect to changing routes, and finally 4) the overall system security increases. We provide a qualitative comparison of available approaches, point out their strengths, respectively weaknesses, and investigate opportunities for further research.
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paper_title: CDA: concealed data aggregation for reverse multicast traffic in wireless sensor networks

paper_content:

End-to-end encryption for wireless sensor networks is a challenging problem. To save the overall energy resources of the network, it is agreed that sensed data need to be consolidated and aggregated on their way to the final destination. We present an approach that (1) conceals sensed data end-to-end, by (2) still providing efficient in-network data aggregation. The aggregating intermediate nodes are not required to operate on the sensed plaintext data. We apply a particular class of encryption transformation and exemplarily discuss the approach on the basis of two aggregation functions. We use actual implementation to show that the approach is feasible and flexible and frequently even more energy efficient than hop-by-hop encryption.
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paper_title: Secure comparison of encrypted data in wireless sensor networks

paper_content:

End-to-end encryption schemes that support operations over ciphertext are of utmost importance for commercial private party wireless sensor network implementations to become meaningful and profitable. For wireless sensor networks, we demonstrated in our previous work that privacy homomorphisms, when used for this purpose, offer two striking advantages apart from end-to-end concealment of data and ability to operate on ciphertexts: flexibility by keyless aggregation and conservation and balancing of aggregator backbone energy. We offered proof of concept by applying a certain privacy homomorphism for sensor network applications that rely on the addition operation. But a large class of aggregator functions like median computation or finding maximum/minimum rely exclusively on comparison operations. Unfortunately, as shown by Rivest, et al., any privacy homomorphism is insecure even against ciphertext that only attacks if they support comparison operations. In this paper we show that a particular order preserving encryption scheme achieves the above mentioned energy benefits and flexibility when used to support comparison operations over encrypted texts for wireless sensor networks, while also managing to hide the plaintext distribution and being secure against ciphertext only attacks. The scheme is shown to have reasonable memory and computation overhead when applied for wireless sensor networks.
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paper_title: SIA: Secure information aggregation in sensor networks

paper_content:

In sensor networks, data aggregation is a vital primitive enabling efficient data queries. An on-site aggregator device collects data from sensor nodes and produces a condensed summary which is forwarded to the off-site querier, thus reducing the communication cost of the query. Since the aggregator is on-site, it is vulnerable to physical compromise attacks. A compromised aggregator may report false aggregation results. Hence, it is essential that techniques are available to allow the querier to verify the integrity of the result returned by the aggregator node. ::: ::: We propose a novel framework for secure information aggregation in sensor networks. By constructing efficient random sampling mechanisms and interactive proofs, we enable the querier to verify that the answer given by the aggregator is a good approximation of the true value, even when the aggregator and a fraction of the sensor nodes are corrupted. In particular, we present efficient protocols for secure computation of the median and average of the measurements, for the estimation of the network size, for finding the minimum and maximum sensor reading, and for random sampling and leader election. Our protocols require only sublinear communication between the aggregator and the user.
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paper_title: Energy-Efficient Secure Pattern Based Data Aggregation for Wireless Sensor Networks

paper_content:

Data aggregation in wireless sensor networks eliminates redundancy to improve bandwidth utilization and energy-efficiency of sensor nodes. This paper presents a secure energy-efficient data aggregation protocol called ESPDA (Energy-Efficient Secure Pattern based Data Aggregation). Unlike conventional data aggregation techniques, ESPDA prevents the redundant data transmission from sensor nodes to cluster-heads. If sensor nodes sense the same data, ESPDA first puts all but one of them into sleep mode and generate pattern codes to represent the characteristics of data sensed by sensor nodes. Cluster-heads implement data aggregation based on pattern codes and only distinct data in encrypted form is transmitted from sensor nodes to the base station via cluster-heads. Due to the use of pattern codes, cluster-heads do not need to know the sensor data to perform data aggregation, which allows sensor nodes to establish secure end-to-end communication links with base station. Therefore, there is no need for encryption/decryption key distribution between the cluster-heads and sensor nodes. Moreover, the use of NOVSF Block-Hopping technique improves the security by randomly changing the mapping of data blocks to NOVSF time slots. Performance evaluation shows that ESPDA outperforms conventional data aggregation methods up to 50% in bandwidth efficiency.
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paper_title: Efficient and provably secure aggregation of encrypted data in wireless sensor networks

paper_content:

Wireless sensor networks (WSNs) are composed of tiny devices with limited computation and battery capacities. For such resource-constrained devices, data transmission is a very energy-consuming operation. To maximize WSN lifetime, it is essential to minimize the number of bits sent and received by each device. One natural approach is to aggregate sensor data along the path from sensors to the sink. Aggregation is especially challenging if end-to-end privacy between sensors and the sink (or aggregate integrity) is required. In this article, we propose a simple and provably secure encryption scheme that allows efficient additive aggregation of encrypted data. Only one modular addition is necessary for ciphertext aggregation. The security of the scheme is based on the indistinguishability property of a pseudorandom function (PRF), a standard cryptographic primitive. We show that aggregation based on this scheme can be used to efficiently compute statistical values, such as mean, variance, and standard deviation of sensed data, while achieving significant bandwidth savings. To protect the integrity of the aggregated data, we construct an end-to-end aggregate authentication scheme that is secure against outsider-only attacks, also based on the indistinguishability property of PRFs.
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paper_title: Concealed Data Aggregation for Reverse Multicast Traffic in Sensor Networks: Encryption, Key Distribution, and Routing Adaptation

paper_content:

Routing in wireless sensor networks is different from that in commonsense mobile ad-hoc networks. It mainly needs to support reverse multicast traffic to one particular destination in a multihop manner. For such a communication pattern, end-to-end encryption is a challenging problem. To save the overall energy resources of the network, sensed data needs to be consolidated and aggregated on its way to the final destination. We present an approach that 1) conceals sensed data end-to-end by 2) still providing efficient and flexible in-network data aggregation. The aggregating intermediate nodes are not required to operate on the sensed plaintext data. We apply a particular class of encryption transformations and discuss techniques for computing the aggregation functions "average" and "movement detection." We show that the approach is feasible for the class of "going down" routing protocols. We consider the risk of corrupted sensor nodes by proposing a key predistribution algorithm that limits an attacker's gain and show how key predistribution and a key-ID sensitive "going down" routing protocol help increase the robustness and reliability of the connected backbone
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paper_title: A witness-based approach for data fusion assurance in wireless sensor networks

paper_content:

In wireless sensor networks, sensor nodes are spread randomly over the coverage area to collect information of interest. Data fusion is used to process these collected information before they are sent to the base station, the observer of the sensor network. We study the security of the data fusion process in this work. In particular, we propose a witness-based solution to assure the validation of the data sent from data fusion nodes to the base station. We also present the theoretical analysis for the overhead associated with the mechanism, which indicates that even in an extremely harsh environment the overhead is low for the proposed mechanism.
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paper_title: PDA: Privacy-Preserving Data Aggregation in Wireless Sensor Networks

paper_content:

Providing efficient data aggregation while preserving data privacy is a challenging problem in wireless sensor networks research. In this paper, we present two privacy-preserving data aggregation schemes for additive aggregation functions. The first scheme -cluster-based private data aggregation (CPDA)-leverages clustering protocol and algebraic properties of polynomials. It has the advantage of incurring less communication overhead. The second scheme -Slice-Mix-AggRegaTe (SMART)-builds on slicing techniques and the associative property of addition. It has the advantage of incurring less computation overhead. The goal of our work is to bridge the gap between collaborative data collection by wireless sensor networks and data privacy. We assess the two schemes by privacy-preservation efficacy, communication overhead, and data aggregation accuracy. We present simulation results of our schemes and compare their performance to a typical data aggregation scheme -TAG, where no data privacy protection is provided. Results show the efficacy and efficiency of our schemes. To the best of our knowledge, this paper is among the first on privacy-preserving data aggregation in wireless sensor networks.
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paper_title: Secure aggregation for wireless networks

paper_content:

An emerging class of important applications uses ad hoc wireless networks of low-power sensor devices to monitor and send information about a possibly hostile environment to a powerful base station connected to a wired network. To conserve power, intermediate network nodes should aggregate results from individual sensors. However, this opens the risk that a single compromised sensor device can render the network useless, or worse, mislead the operator into trusting a false reading. We present a protocol that provides a secure aggregation mechanism for wireless networks that is resilient to both intruder devices and single device key compromises. Our protocol is designed to work within the computation, memory and power consumption limits of inexpensive sensor devices, but takes advantage of the properties of wireless networking, as well as the power asymmetry between the devices and the base station.
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paper_title: Secure verification of location claims

paper_content:

With the growing prevalence of sensor and wireless networks comes a new demand for location-based access control mechanisms. We introduce the concept of secure location verification, and we show how it can be used for location-based access control. Then, we present the Echo protocol, a simple method for secure location verification. The Echo protocol is extremely lightweight: it does not require time synchronization, cryptography, or very precise clocks. Hence, we believe that it is well suited for use in small, cheap, mobile devices.
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paper_title: Tamper Resistance -- a Cautionary Note

paper_content:

An increasing number of systems from pay-TV to electronic purses, rely on the tamper resistance of smartcards and other security processors. We describe a number of attacks on such systems -- some old, some new and some that are simply little known outside the chip testing community. We conclude that trusting tamper resistance is problematic; smartcards are broken routinely, and even a device that was described by a government signals agency as 'the most secure processor generally available' turns out to be vulnerable. Designers of secure systems should consider the consequences with care.
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paper_title: SWATT: softWare-based attestation for embedded devices

paper_content:

We expect a future where we are surrounded by embedded devices, ranging from Java-enabled cell phones to sensor networks and smart appliances. An adversary can compromise our privacy and safety by maliciously modifying the memory contents of these embedded devices. In this paper, we propose a softWare-based attestation technique (SWATT) to verify the memory contents of embedded devices and establish the absence of malicious changes to the memory contents. SWATT does not need physical access to the device's memory, yet provides memory content attestation similar to TCG or NGSCB without requiring secure hardware. SWATT can detect any change in memory contents with high probability, thus detecting viruses, unexpected configuration settings, and Trojan Horses. To circumvent SWATT, we expect that an attacker needs to change the hardware to hide memory content changes. We present an implementation of SWATT in off-the-shelf sensor network devices, which enables us to verify the contents of the program memory even while the sensor node is running.
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paper_title: INSENS: Intrusion-Tolerant Routing in Wireless Sensor Networks

paper_content:

This paper describes an INtrusion-tolerant routing protocol for wireless SEnsor NetworkS (INSENS). INSENS securely and efficiently constructs tree-structured routing for wireless sensor networks (WSNs). The key objective of an INSENS network is to tolerate damage caused by an intruder who has compromised deployed sensor nodes and is intent on injecting, modifying, or blocking packets. To limit or localize the damage caused by such an intruder, INSENS incorporates distributed lightweight security mechanisms, including efficient one-way hash chains and nested keyed message authentication codes that defend against wormhole attacks, as well as multipath routing. Adapting to WSN characteristics, the design of INSENS also pushes complexity away from resource-poor sensor nodes towards resource-rich base stations. An enhanced single-phase version of INSENS scales to large networks, integrates bidirectional verification to defend against rushing attacks, accommodates multipath routing to multiple base stations, enables secure joining/leaving, and incorporates a novel pairwise key setup scheme based on transitory global keys that is more resilient than LEAP. Simulation results are presented to demonstrate and assess the tolerance of INSENS to various attacks launched by an adversary. A prototype implementation of INSENS over a network of MICA2 motes is presented to evaluate the cost incurred.
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paper_title: Denial of Service in Sensor Networks

paper_content:

Sensor networks hold the promise of facilitating large-scale, real-time data processing in complex environments, helping to protect and monitor military, environmental, safety-critical, or domestic infrastructures and resources, Denial-of-service attacks against such networks, however, may permit real world damage to public health and safety. Without proper security mechanisms, networks will be confined to limited, controlled environments, negating much of the promise they hold. The limited ability of individual sensor nodes to thwart failure or attack makes ensuring network availability more difficult. To identify denial-of-service vulnerabilities, the authors analyzed two effective sensor network protocols that did not initially consider security. These examples demonstrate that consideration of security at design time is the best way to ensure successful network deployment.
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paper_title: Low Cost Attacks on Tamper Resistant Devices

paper_content:

There has been considerable recent interest in the level of tamper resistance that can be provided by low cost devices such as smart-cards. It is known that such devices can be reverse engineered using chip testing equipment, but a state of the art semiconductor laboratory costs millions of dollars. In this paper, we describe a number of attacks that can be mounted by opponents with much shallower pockets. Three of them involve special (but low cost) equipment: differential fault analysis, chip rewriting, and memory remanence. There are also attacks based on good old fashioned protocol failure which may not require any special equipment at all. We describe and give examples of each of these. Some of our attacks are significant improvements on the state of the art; others are useful cautionary tales. Together, they show that building tamper resistant devices, and using them effectively, is much harder than it looks.
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paper_title: Challenges in intrusion detection for wireless ad-hoc networks

paper_content:

This paper presents a brief survey of current research in intrusion detection for wireless ad-hoc networks. In addition to examining the challenges of providing intrusion detection in this environment, this paper reviews current efforts to detect attacks against the ad-hoc routing infrastructure, as well as detecting attacks directed against the mobile nodes. This paper also examines the intrusion detection architectures that may be deployed for different wireless ad-hoc network infrastructures, as well as proposed methods of intrusion response.
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paper_title: On supporting distributed collaboration in sensor networks

paper_content:

In sensor networks, nodes may malfunction due to the hostile environment. Therefore, dealing with node failure is a very important research issue. In this paper, we study distributed cooperative failure detection techniques. In the proposed techniques, the nodes around a suspected node collaborate with each other to reach an agreement on whether the suspect is faulty or malicious. We first formalize the problem as how to construct a dominating tree to cover all the neighbors of the suspect and give the lower bound of the message complexity. Two tree-based propagation collection protocols are proposed to construct dominating trees and collect information via the tree structure. Instead of using the traditional flooding technique, we propose a coverage-based heuristic to improve the system performance. Theoretical analysis and simulation results show that the heuristic can help achieve a higher tree coverage with lower message complexity, lower delay and lower energy consumption.
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paper_title: Denial of Service in Sensor Networks

paper_content:

Sensor networks hold the promise of facilitating large-scale, real-time data processing in complex environments, helping to protect and monitor military, environmental, safety-critical, or domestic infrastructures and resources, Denial-of-service attacks against such networks, however, may permit real world damage to public health and safety. Without proper security mechanisms, networks will be confined to limited, controlled environments, negating much of the promise they hold. The limited ability of individual sensor nodes to thwart failure or attack makes ensuring network availability more difficult. To identify denial-of-service vulnerabilities, the authors analyzed two effective sensor network protocols that did not initially consider security. These examples demonstrate that consideration of security at design time is the best way to ensure successful network deployment.
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paper_title: An interleaved hop-by-hop authentication scheme for filtering of injected false data in sensor networks

paper_content:

Sensor networks are often deployed in unattended environments, thus leaving these networks vulnerable to false data injection attacks in which an adversary injects false data into the network with the goal of deceiving the base station or depleting the resources of the relaying nodes. Standard authentication mechanisms cannot prevent this attack if the adversary has compromised one or a small number of sensor nodes. In this paper, we present an interleaved hop-by-hop authentication scheme that guarantees that the base station will detect any injected false data packets when no more than a certain number t nodes are compromised. Further, our scheme provides an upper bound B for the number of hops that a false data packet could be forwarded before it is detected and dropped, given that there are up to t colluding compromised nodes. We show that in the worst case B is O(t/sup 2/). Through performance analysis, we show that our scheme is efficient with respect to the security it provides, and it also allows a tradeoff between security and performance.
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paper_title: Security in Ad Hoc Networks : a General Intrusion Detection Architecture Enhancing Trust Based Approaches

paper_content:

In the last few years, the performances of wireless technologies have increased tremendously thus opening new fields of application in the domain of networking. One of such fields concerns mobile ad hoc networks (MANETs) in which mobile nodes organise themselves in a network without the help of any predefined infrastructure. Securing MANETs is just as important, if not more, as securing traditional wired networks. Existing solutions can be used to obtain a certain level of security. Nevertheless, these solutions may not always be suitable to wireless networks. Furthermore, ad hoc networks have their own vulnerabilities that cannot be tackled by these solutions. To obtain an acceptable level of security in such a context, traditional security solutions should be coupled with an intrusion detection mechanism. In this paper we show how ad hoc networks can be, to a certain extent, secured using traditional techniques. We then examine the different intrusion detection techniques and point out the reasons why they usually cannot be used in an ad hoc context. Finally, we go through the requirements of an intrusion detection system for ad hoc networks, and define an adapted architecture for an intrusion detection system for manets.
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paper_title: An Intrusion Detection Architecture for Clustered Wireless Ad Hoc Networks

paper_content:

For the shortcomings of the existing single-function management systems of electric power marketing management at present, the energy acquisition and operation management system based on the customized integrated services distribution automation terminal is proposed, using wireless ad-hoc networks and wireless mesh networking technology to solve the 'last mile' problem in the distribution automation system. As an instance of a wireless sensor network (WSN), it provides a highly reliable, real-time on-site intelligent network with strong adaptability to environment. This paper describes the structure of the energy acquisition and operation management system, and it's the uplink downlink communication channels and interfaces. The main function module design and system characteristics are detailed. The system seamlessly integrates power on-site management system, distribution transformer management system and automatic meter reading system, with a new intensive, diversified, practical system to replace the previous single-function systems.
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paper_title: Highly reliable trust establishment scheme in ad hoc networks

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Securing ad hoc networks in a fully self-organized way is effective and light-weight, but fails to accomplish trust initialization in many trust deficient scenarios. To overcome this problem, this paper aims at building well established trust relationships in ad hoc networks without relying on any pre-defined assumption. We propose a probabilistic solution based on distributed trust model. A secret dealer is introduced only in the system bootstrapping phase to complement the assumption in trust initialization. With it, much shorter and more robust trust chains are able to be constructed with high probability. A fully self-organized trust establishment approach is then adopted to conform to the dynamic membership changes. The simulation results on both static and dynamic performances show that our scheme is highly resilient to dynamic membership changing and scales well. The lack of initial trust establishment mechanisms in most higher level security solutions (e.g. key management schemes, secure routing protocols) for ad hoc networks makes them benefit from our scheme.
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paper_title: Establishing Trust In Pure Ad-hoc Networks

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An ad-hoc network of wireless nodes is a temporarily formed network, created, operated and managed by the nodes themselves. It is also often termed an infrastructure-less, self-organized, or spontaneous network. Nodes assist each other by passing data and control packets from one node to another, often beyond the wireless range of the original sender. The execution and survival of an ad-hoc network is solely dependent upon the cooperative and trusting nature of its nodes.However, this naive dependency on intermediate nodes makes the ad-hoc network vulnerable to passive and active attacks by malicious nodes. A number of protocols have been developed to secure ad-hoc networks using cryptographic schemes, but all rely on the presence of an omnipresent, and often omniscient, trust authority. As this paper describes, dependence on a central trust authority is an impractical requirement for ad-hoc networks. We present a model for trust-based communication in ad-hoc networks that also demonstrates that a central trust authority is a superfluous requirement. The model introduces the notion of belief and provides a dynamic measure of reliability and trustworthiness in an ad hoc network.
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paper_title: Enforcing cooperative resource sharing in untrusted peer-to-peer environment

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Peer-to-Peer (P2P) computing is widely recognized as a promising paradigm for building next generation distributed applications. However, the autonomous, heterogeneous, and decentralized nature of participating peers introduces the following challenge for resource staring: how to make peers profitable in the untrusted P2P environment? To address the problem, we present a self-policing and distributed approach by combining two models: PET, a personalized trust model, and M-CUBE, a multiple-currency based economic model, to lay a foundation for resource sharing in untrusted P2P computing environments. PET is a flexible trust model that can adapt to different requirements, and provides the solid support for the currency management in M-CUBE. M-CUBE provides a novel self-policing and quality-aware framework for the sharing of multiple resources, including both homogeneous and heterogeneous resources. We evaluate the efficacy and performance of this approach in the context of a real application, a peer-to-peer Web server sharing. Our results show that our approach is flexible enough to adapt to different situations and effective to make the system profitable, especially for systems with large scale.
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paper_title: Peer-to-Peer: Harnessing the Power of Disruptive Technologies

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From the Publisher: ::: Upstart software projects Napster, Gnutella, and Freenet have dominated newspaper headlines, challenging traditional approaches to content distribution with their revolutionary use of peer-to-peer file-sharing technologies. Reporters try to sort out the ramifications of seemingly ungoverned peer-to-peer networks. Lawyers, business leaders, and social commentators debate the virtues and evils of these bold new distributed systems. But what's really behind such disruptive technologies -- the breakthrough innovations that have rocked the music and media worlds? And what lies ahead? ::: In this book, key peer-to-peer pioneers take us beyond the headlines and hype and show how the technology is changing the way we communicate and exchange information. Those working to advance peer-to-peer as a technology, a business opportunity, and an investment offer their insights into how the technology has evolved and where it's going. They explore the problems they've faced, the solutions they've discovered, the lessons they've learned, and their goals for the future of computer networking. ::: Until now, Internet communities have been limited by the flat interactive qualities of email and network newsgroups, where people can exchange recommendations and ideas but have great difficulty commenting on one another's postings, structuring information, performing searches, and creating summaries. Peer-to-peer challenges the traditional authority of the client/server model, allowing shared information to reside instead with producers and users. Peer-to-peer networks empower users to collaborate on producing and consuming information, adding to it, commenting on it, and building communities around it. ::: This compilation represents the collected wisdom of today's peer-to-peer luminaries. It includes contributions from Gnutella's Gene Kan, Freenet's Brandon Wiley, Jabber's Jeremie Miller, and many others -- plus serious discussions of topics ranging from accountability and trust to security and performance. Fraught with questions and promise, peer-to-peer is sure to remain on the computer industry's center stage for years to come.
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paper_title: Trust evaluation based security solution in ad hoc networks

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Ad hoc networks are new paradigm of networks offering unrestricted mobility without any underlying infrastructure. The ad hoc networks have salient characteristics that are totally different from conventional networks. These cause extra challenges on security. In an ad hoc network, each node should not trust any peer. However, traditional cryptographic solution is useless against threats from internal compromised nodes. Thus, new mechanisms are needed to provide effective security solution for the ad hoc networks. In this paper, a trust evaluation based security solution is proposed to provide effective security decision on data protection, secure routing and other network activities. Logical and computational trust analysis and evaluation are deployed among network nodes. Each node's evaluation of trust on other nodes should be based on serious study and inference from such trust factors as experience statistics, data value, intrusion detection result, and references of other nodes, as well as node owner's preference and policy. In order to prove the applicability of the proposed solution, authors further present a routing protocol and analyze its security over several active attacks.
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paper_title: Reputation-based framework for high integrity sensor networks

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The traditional approach of providing network security has been to borrow tools from cryptography and authentication. However, we argue that the conventional view of security based on cryptography alone is not sufficient for the unique characteristics and novel misbehaviors encountered in sensor networks. Fundamental to this is the observation that cryptography cannot prevent malicious or non-malicious insertion of data from internal adversaries or faulty nodes. We believe that in general tools from different domains such as economics, statistics and data analysis will have to be combined with cryptography for the development of trustworthy sensor networks. Following this approach, we propose a reputation-based framework for sensor networks where nodes maintain reputation for other nodes and use it to evaluate their trustworthiness. We will show that this framework provides a scalable, diverse and a generalized approach for countering all types of misbehavior resulting from malicious and faulty nodes. We are currently developing a system within this framework where we employ a Bayesian formulation, specifically a beta reputation system, for reputation representation, updates and integration. We will explain the reasoning behind our design choices, analyzing their pros & cons. We conclude the paper by verifying the efficacy of this system through some preliminary simulation results.
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paper_title: Reputation- and Trust-Based Systems for Wireless Self-organizing Networks

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Traditional approach of providing network security has been to borrow tools and mechanisms from cryptography. However, the conventional view of security based on cryptography alone is not sufficient for the defending against unique and novel types of misbehavior exhibited by nodes in wireless self-organizing networks such as mobile ad hoc networks and wireless sensor networks. Reputation-based frameworks, where nodes maintain reputation of other nodes and use it to evaluate their trustworthiness, are deployed to provide scalable, diverse and a generalized approach for countering different types of misbehavior resulting form malicious and selfish nodes in these networks. In this chapter, we present a comprehensive discussion on reputation and trust-based systems for wireless self-organizing networks. Different classes of reputation system are described along with their unique characteristics and working principles. A number of currently used reputation systems are critically reviewed and compared with respect to their effectiveness and efficiency of performance. Some open problems in the area of reputation and trust-based system within the domain of wireless self-organizing networks are also discussed.
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paper_title: Computing of trust in wireless networks

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The concept of small world in the context of wireless networks, first studied by A. Helmy (see IEEE Commun. Lett., vol.7, no.10, 2003), enables a path-finder to find paths from a source node to a designated target node in efficiently wireless networks. Based on this observation, we provide a practical approach to compute trust in wireless networks by viewing an individual mobile device as a node of a delegation graph, G, and mapping a delegation path from the source node, S, to the target node, T, into an edge in the correspondent transitive closure of the graph, G, from which a trust value is computed.
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paper_title: Mobile Jamming Attack and its Countermeasure in Wireless Sensor Networks

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Denial-of-service (DoS) attacks are serious threats due to the resources constrained property in wireless sensor networks. Jamming attacks are the representative energy-consumption DoS attacks that can be launched easily. Hence, many countermeasures have been proposed to mitigate the damage causing by jamming attacks. In this paper, we first present a novel and powerful jamming attack called mobile jamming attack. Besides, we propose a multi-dataflow topologies scheme that can effectively defend the mobile jamming attack. The simulation results demonstrate that the mobile jamming attack is more devastating than traditional jamming attacks and the proposed defense scheme can effectively alleviate the damage.
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paper_title: Scalable, Cluster-based Anti-replay Protection for Wireless Sensor Networks

paper_content:

Large-scale wireless sensor network (WSN) deployments show great promise for military, homeland security, and many other applications. This promise, however, is offset by important security concerns. The resource constraints that typify wireless sensor devices make traditional security solutions impractical. One threat to secure sensor networks is the replay attack, in which packets are captured and replayed into the network. This type of attack can be perpetrated to confuse observers or to mount a denial-of-service or denial-of-sleep attack. Traditional techniques for anti-replay protection are too resource intensive for large-scale WSN deployments. While techniques for reducing data transmission overhead of WSN-speciflc anti-replay mechanisms have been explored, the important problem of minimizing per-node reply table storage requirements has not been addressed. This paper introduces Clustered Anti-Replay Protection or CARP, which leverages sensor network clustering to place a limit on the amount of memory required to store anti-replay information. We show that clustering keeps the memory required for anti-replay tables manageable, reducing the size from 30% of a Mica2's memory to 4.4% for a 200-node network. While the advantages of this technique are clear, the difficulty lies in securely updating network-wide anti-replay tables when the network reclusters, an event that must happen routinely to distribute energy consumption across the nodes in the network. Our mechanism distributes necessary anti-replay information in a secure, low-overhead, and completely distributed manner. We further show the energy-consumption overhead of adding anti-replay counters to network traffic across several WSN medium access control (MAC) protocols and two representative WSN platforms. On the Mica2 platform, overheads range from a 0% to 1.32% decrease in network lifetime, depending on the MAC protocol. On the Tmote Sky, overheads range from 0% to 4.64%. Providing anti-replay support in a secure, scalable, and distributed way is necessary to the overall security of future WSN deployments if they are to meet current expectations.
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paper_title: Security in Cognitive Radio Networks: Threats and Mitigation

paper_content:

This paper describes a new class of attacks specific to cognitive radio networks. Wireless devices that can learn from their environment can also be taught things by malicious elements of their environment. By putting artificial intelligence in charge of wireless network devices, we are allowing unanticipated, emergent behavior, fitting a perhaps distorted or manipulated level of optimality. The state space for a cognitive radio is made up of a variety of learned beliefs and current sensor inputs. By manipulating radio sensor inputs, an adversary can affect the beliefs of a radio, and consequently its behavior. In this paper we focus primarily on PHY-layer issues, describing several classes of attacks and giving specific examples for dynamic spectrum access and adaptive radio scenarios. These attacks demonstrate the capabilities of an attacker who can manipulate the spectral environment when a radio is learning. The most powerful of which is a self-propagating AI virus that could interactively teach radios to become malicious. We then describe some approaches for mitigating the effectiveness of these attacks by instilling some level of "common sense" into radio systems, and requiring learned beliefs to expire and be relearned. Lastly we provide a road-map for extending these ideas to higher layers in the network stack.
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paper_title: Defense against Primary User Emulation Attacks in Cognitive Radio Networks

paper_content:

Cognitive radio (CR) is a promising technology that can alleviate the spectrum shortage problem by enabling unlicensed users equipped with CRs to coexist with incumbent users in licensed spectrum bands while causing no interference to incumbent communications. Spectrum sensing is one of the essential mechanisms of CRs and its operational aspects are being investigated actively. However, the security aspects of spectrum sensing have garnered little attention. In this paper, we identify a threat to spectrum sensing, which we call the primary user emulation (PUE) attack. In this attack, an adversary's CR transmits signals whose characteristics emulate those of incumbent signals. The highly flexible, software-based air interface of CRs makes such an attack possible. Our investigation shows that a PUE attack can severely interfere with the spectrum sensing process and significantly reduce the channel resources available to legitimate unlicensed users. To counter this threat, we propose a transmitter verification scheme, called LocDef (localization-based defense), which verifies whether a given signal is that of an incumbent transmitter by estimating its location and observing its signal characteristics. To estimate the location of the signal transmitter, LocDef employs a non-interactive localization scheme. Our security analysis and simulation results suggest that LocDef is effective in identifying PUE attacks under certain conditions.
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paper_title: Ensuring Trustworthy Spectrum Sensing in Cognitive Radio Networks

paper_content:

Cognitive Radio (CR) is a promising technology that can alleviate the spectrum shortage problem by enabling unlicensed users equipped with CRs to coexist with incumbent users in licensed spectrum bands without inducing interference to incumbent communications. Spectrum sensing is one of the essential mechanisms of CRs that has attracted great attention from researhers recently. Although the operational aspects of spectrum sensing are being investigated actively, its security aspects have garnered little attention. In this paper, we describe an attack that poses a great threat to spectrum sensing. In this attack, which is called the primary user emulation (PUE) attack, an adversary's CR transmits signals whose characteristics emulate those of incumbent signals. The highly flexible, software-based air interface of CRs makes such an attack possible. Our investigation shows that a PUE attack can severely interfere with the spectrum sensing process and significantly reduce the channel resources available to legitimate unlicensed users. As a way of countering this threat, we propose a transmitter verification procedure that can be integrated into the spectrum sensing mechanism. The transmitter verification procedure employs a location verification scheme to distinguish incumbent signals from unlicensed signals masquerading as incumbent signals. Two alternative techniques are proposed to realize location verification: Distance Ratio Test and Distance Difference Test. We provide simulation results of the two techniques as well as analyses of their security in the paper.
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paper_title: Security in Cognitive Radio Networks: Threats and Mitigation

paper_content:

This paper describes a new class of attacks specific to cognitive radio networks. Wireless devices that can learn from their environment can also be taught things by malicious elements of their environment. By putting artificial intelligence in charge of wireless network devices, we are allowing unanticipated, emergent behavior, fitting a perhaps distorted or manipulated level of optimality. The state space for a cognitive radio is made up of a variety of learned beliefs and current sensor inputs. By manipulating radio sensor inputs, an adversary can affect the beliefs of a radio, and consequently its behavior. In this paper we focus primarily on PHY-layer issues, describing several classes of attacks and giving specific examples for dynamic spectrum access and adaptive radio scenarios. These attacks demonstrate the capabilities of an attacker who can manipulate the spectral environment when a radio is learning. The most powerful of which is a self-propagating AI virus that could interactively teach radios to become malicious. We then describe some approaches for mitigating the effectiveness of these attacks by instilling some level of "common sense" into radio systems, and requiring learned beliefs to expire and be relearned. Lastly we provide a road-map for extending these ideas to higher layers in the network stack.
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paper_title: Security and privacy of collaborative spectrum sensing in cognitive radio networks

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Collaborative spectrum sensing is regarded as a promising approach to significantly improve the performance of spectrum sensing in cognitive radio networks. However, due to the open nature of wireless communications and the increasingly available software defined radio platforms, collaborative spectrum sensing also poses many new research challenges, especially in the aspect of security and privacy. In this article, we first identify the potential security threats toward collaborative spectrum sensing in CRNs. Then we review the existing proposals related to secure collaborative spectrum sensing. Furthermore, we identify several new location privacy related attacks in collaborative sensing, which are expected to compromise secondary users? location privacy by correlating their sensing reports and their physical location. To thwart these attacks, we propose a novel privacy preserving framework in collaborative spectrum sensing to prevent location privacy leaking. We design and implement a real-world testbed to evaluate the system performance. The attack experiment results show that if there is no any security guarantee, the attackers could successfully compromise a secondary user?s location privacy at a success rate of more than 90 percent. We also show that the proposed privacy preserving framework could significantly improve the location privacy of secondary users with a minimal effect on the performance of collaborative sensing.
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paper_title: Cognitive Spectrum and Its Security Issues

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The current trend for opportunistic use of the licensed or licensed-exempt wireless spectrum with limited rules, or even without rules, introduces significant scientific and technical challenges for the networks of the future. Until now, for the realization of the cognitive radio paradigm, several spectrum sharing schemes have been proposed, such as centralized and distributed schemes, and cooperative or noncooperative spectrum sharing mechanisms. Unfortunately, some of the existing proposals for spectrum sharing and management introduce significant security leakages, putting into effect unfairness, unavailability, and selfishness, or even malicious behaviors. Additionally, the identification, recording and reporting of selfish, free-riders, malicious and anomalous actions by peers is still an open issue in the majority of the existing spectrum management schemes. This paper discusses and classifies the weak points and the vulnerabilities of the spectrum sharing mechanisms.
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paper_title: Security in Cognitive Radio Networks: The Required Evolution in Approaches to Wireless Network Security

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This paper discusses the topic of wireless security in cognitive radio networks, delineating the key challenges in this area. With the ever-increasing scarcity of spectrum, cognitive radios are expected to become an increasingly important part of the overall wireless networking landscape. However, there is an important technical area that has received little attention to date in the cognitive radio paradigm: wireless security. The cognitive radio paradigm introduces entirely new classes of security threats and challenges, and providing strong security may prove to be the most difficult aspect of making cognitive radio a long-term commercially-viable concept. This paper delineates the key challenges in providing security in cognitive networks, discusses the current security posture of the emerging IEEE 802.22 cognitive radio standard, and identifies potential vulnerabilities along with potential mitigation approaches.
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paper_title: Jamming and sensing of encrypted wireless ad hoc networks

paper_content:

This paper considers the problem of an attacker disrupting an encrypted victim wireless ad hoc network through jamming. Jamming is broken down into layers and this paper focuses on jamming at the Transport/Network layer. Jamming at this layer exploits AODV and TCP protocols and is shown to be very effective in simulated and real networks when it can sense victim packet types, but the encryption is assumed to mask the entire header and contents of the packet so that only packet size, timing, and sequence is available to the attacker for sensing. A sensor is developed that consists of four components. The first is a probabilistic model of the sizes and inter-packet timing of different packet types. The second is a historical method for detecting known protocol sequences that is used to develop the probabilistic models, the third is an active jamming mechanism to force the victim network to produce known sequences for the historical analyzer, and the fourth is the online classifier that makes packet type classification decisions. The method is tested on live data and found that for many packet types the classification is highly reliable. The relative roles of size, timing, and sequence are discussed along with the implications for making networks more secure.
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paper_title: The feasibility of launching and detecting jamming attacks in wireless networks

paper_content:

Wireless networks are built upon a shared medium that makes it easy for adversaries to launch jamming-style attacks. These attacks can be easily accomplished by an adversary emitting radio frequency signals that do not follow an underlying MAC protocol. Jamming attacks can severely interfere with the normal operation of wireless networks and, consequently, mechanisms are needed that can cope with jamming attacks. In this paper, we examine radio interference attacks from both sides of the issue: first, we study the problem of conducting radio interference attacks on wireless networks, and second we examine the critical issue of diagnosing the presence of jamming attacks. Specifically, we propose four different jamming attack models that can be used by an adversary to disable the operation of a wireless network, and evaluate their effectiveness in terms of how each method affects the ability of a wireless node to send and receive packets. We then discuss different measurements that serve as the basis for detecting a jamming attack, and explore scenarios where each measurement by itself is not enough to reliably classify the presence of a jamming attack. In particular, we observe that signal strength and carrier sensing time are unable to conclusively detect the presence of a jammer. Further, we observe that although by using packet delivery ratio we may differentiate between congested and jammed scenarios, we are nonetheless unable to conclude whether poor link utility is due to jamming or the mobility of nodes. The fact that no single measurement is sufficient for reliably classifying the presence of a jammer is an important observation, and necessitates the development of enhanced detection schemes that can remove ambiguity when detecting a jammer. To address this need, we propose two enhanced detection protocols that employ consistency checking. The first scheme employs signal strength measurements as a reactive consistency check for poor packet delivery ratios, while the second scheme employs location information to serve as the consistency check. Throughout our discussions, we examine the feasibility and effectiveness of jamming attacks and detection schemes using the MICA2 Mote platform.
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paper_title: Implementation issues in spectrum sensing for cognitive radios

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There are new system implementation challenges involved in the design of cognitive radios, which have both the ability to sense the spectral environment and the flexibility to adapt transmission parameters to maximize system capacity while coexisting with legacy wireless networks. The critical design problem is the need to process multigigahertz wide bandwidth and reliably detect presence of primary users. This places severe requirements on sensitivity, linearity and dynamic range of the circuitry in the RF front-end. To improve radio sensitivity of the sensing function through processing gain we investigated three digital signal processing techniques: matched filtering, energy detection and cyclostationary feature detection. Our analysis shows that cyclostationary feature detection has advantages due to its ability to differentiate modulated signals, interference and noise in low signal to noise ratios. In addition, to further improve the sensing reliability, the advantage of a MAC protocol that exploits cooperation among many cognitive users is investigated.
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paper_title: Defense against Primary User Emulation Attacks in Cognitive Radio Networks

paper_content:

Cognitive radio (CR) is a promising technology that can alleviate the spectrum shortage problem by enabling unlicensed users equipped with CRs to coexist with incumbent users in licensed spectrum bands while causing no interference to incumbent communications. Spectrum sensing is one of the essential mechanisms of CRs and its operational aspects are being investigated actively. However, the security aspects of spectrum sensing have garnered little attention. In this paper, we identify a threat to spectrum sensing, which we call the primary user emulation (PUE) attack. In this attack, an adversary's CR transmits signals whose characteristics emulate those of incumbent signals. The highly flexible, software-based air interface of CRs makes such an attack possible. Our investigation shows that a PUE attack can severely interfere with the spectrum sensing process and significantly reduce the channel resources available to legitimate unlicensed users. To counter this threat, we propose a transmitter verification scheme, called LocDef (localization-based defense), which verifies whether a given signal is that of an incumbent transmitter by estimating its location and observing its signal characteristics. To estimate the location of the signal transmitter, LocDef employs a non-interactive localization scheme. Our security analysis and simulation results suggest that LocDef is effective in identifying PUE attacks under certain conditions.
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paper_title: Security threats to signal classifiers using self-organizing maps

paper_content:

Spectrum sensing is required for many cognitive radio applications, including spectral awareness, interoperability, and dynamic spectrum access. Previous work has demonstrated the ill effects of primary user emulation attacks, and pointed out specific vulnerabilities in spectrum sensing that uses featurebased classifiers. This paper looks specifically at the use of unsupervised learning in signal classifiers, and attacks against self-organizing maps. By temporarily manipulating their signals, attackers can cause other secondary users to permanently misclassify them as primary users, giving them complete access to the spectrum. In the paper we develop the theory behind manipulating the decision regions in a neural network using self-organizing maps. We then demonstrate through simulation the ability for an attacker to formulate the necessary input signals to execute the attack. Lastly we provide recommendations to mitigate the efficacy of this type of attack.
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paper_title: Ensuring Trustworthy Spectrum Sensing in Cognitive Radio Networks

paper_content:

Cognitive Radio (CR) is a promising technology that can alleviate the spectrum shortage problem by enabling unlicensed users equipped with CRs to coexist with incumbent users in licensed spectrum bands without inducing interference to incumbent communications. Spectrum sensing is one of the essential mechanisms of CRs that has attracted great attention from researhers recently. Although the operational aspects of spectrum sensing are being investigated actively, its security aspects have garnered little attention. In this paper, we describe an attack that poses a great threat to spectrum sensing. In this attack, which is called the primary user emulation (PUE) attack, an adversary's CR transmits signals whose characteristics emulate those of incumbent signals. The highly flexible, software-based air interface of CRs makes such an attack possible. Our investigation shows that a PUE attack can severely interfere with the spectrum sensing process and significantly reduce the channel resources available to legitimate unlicensed users. As a way of countering this threat, we propose a transmitter verification procedure that can be integrated into the spectrum sensing mechanism. The transmitter verification procedure employs a location verification scheme to distinguish incumbent signals from unlicensed signals masquerading as incumbent signals. Two alternative techniques are proposed to realize location verification: Distance Ratio Test and Distance Difference Test. We provide simulation results of the two techniques as well as analyses of their security in the paper.
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paper_title: The Sum of Log-Normal Probability Distributions in Scatter Transmission Systems

paper_content:

The long-term fluctuation of transmission loss in scatter propagation systems has been found to have a logarithmicnormal distribution. In other words, the scatter loss in decibels has Gaussian statistical distribution. Therefore, in many important communication systems (e.g., FM), the noise power of a radio jump, or hop, has log-normal statistical distribution. In a multihop system, the noise power of each hop contributes to the total noise. The resulting noise of the system is therefore the statistical sum of the individual noise distributions. In multihop scatter systems and others, such as multichannel speech-transmission systems, the sum of several log-normal distributions is needed. No exact solution to this problem is known. The following discussion presents an approximate solution which is satisfactory in most practical cases. For tactical multihop scatter systems, a further approximation is proposed, which reduces significantly the necessary computation. An example of the computation is given.
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paper_title: Attack-proof collaborative spectrum sensing in cognitive radio networks

paper_content:

Collaborative sensing in cognitive radio networks can significantly improve the probability of detecting the transmission of primary users. In current collaborative sensing schemes, all collaborative secondary users are assumed to be honest. As a consequence, the system is vulnerable to attacks in which malicious secondary users report false detection results. In this paper, we investigate how to improve the security of collaborative sensing. Particularly, we develop a malicious user detection algorithm that calculates the suspicious level of secondary users based on their past reports. Then, we calculate trust values as well as consistency values that are used to eliminate the malicious users' influence on the primary user detection results. Through simulations, we show that even a single malicious user can significantly degrade the performance of collaborative sensing. The proposed trust value indicator can effectively differentiate honest and malicious secondary users. The receiver operating characteristic (ROC) curves for the primary user detection demonstrate the improvement in the security of collaborative sensing.
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paper_title: An Analytical Model for Primary User Emulation Attacks in Cognitive Radio Networks

paper_content:

In this paper, we study the denial-of-service (DoS) attack on secondary users in a cognitive radio network by primary user emulation (PUE). Most approaches in the literature on primary user emulation attacks (PUEA) discuss mechanisms to deal with the attacks but not analytical models. Simulation studies and results from test beds have been presented but no analytical model relating the various parameters that could cause a PUE attack has been proposed and studied. We propose an analytical approach based on Fenton's approximation and Markov inequality and obtain a lower bound on the probability of a successful PUEA on a secondary user by a set of co-operating malicious users. We consider a fading wireless environment and discuss the various parameters that can affect the feasibility of a PUEA. We show that the probability of a successful PUEA increases with the distance between the primary transmitter and secondary users. This is the first analytical treatment to study the feasibility of a PUEA.
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paper_title: CatchIt: Detect Malicious Nodes in Collaborative Spectrum Sensing

paper_content:

Collaborative spectrum sensing in cognitive radio networks has been proposed as an efficient way to improve the performance of primary users detection. In collaborative spectrum sensing schemes, secondary users are often assumed to be trustworthy. In practice, however, cognitive radio nodes can be compromised. Compromised secondary users can report false detection results and significantly degrade the performance of spectrum sensing. In this paper, we investigate the case that there are multiple malicious users in cognitive radio networks and the exact number of malicious users is unknown. An onion-peeling approach is proposed to defense against multiple untrustworthy secondary nodes. We calculate suspicious level of all nodes according to their reports. When the suspicious level of a node is beyond certain threshold, it will be considered as malicious and its report will be excluded in decision-making. We continue to calculate the suspicious level of remaining nodes until no malicious node can be found. Simulation results show that malicious nodes greatly degrade the performance of collaborative sensing, and the proposed scheme can efficiently detect malicious nodes. Compared with existing defense methods, the proposed scheme significantly improves the performance of primary user detection, measured by ROC curves, and captures the dynamic change in the behaviors of malicious users.
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paper_title: Security in cognitive radio networks: An example using the commercial IEEE 802.22 standard

paper_content:

Security in wireless networks is challenging. Security in cognitive radio networks (CRN) is even more challenging. This is because a CRN consists of cognitive radios (CR) which have many more functions and processes to account for, such as sensing, geolocation, spectrum management, access to the policy database etc. Each of these functions and processes need to be assessed for potential vulnerabilities and security mechanisms need to be provided for protection of not just the secondary users of the spectrum but also the primary users or the incumbents. This paper discusses the potential security vulnerabilities and the remediations for the same in a CRN with an example using a commercial IEEE 802.22 standard. Due to the unique characteristics of the CRs in a CRN, enhanced security mechanisms are required. The security mechanisms in CRN are divided into several security sub-layers which protect non-cognitive as well as cognitive functions of the system and the interactions between the two. This paper describes these security features as incorporated into the IEEE 802.22 standard. It is possible to apply similar security mechanisms for a military CRN.
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paper_title: Secure cooperative spectrum sensing for Cognitive Radio networks

paper_content:

A key enabling functionality in implementing Cognitive Radio is to reliably detect the licensed users. In recent literature, cooperation among spectrum sensing terminals is suggested to offer reliable sensing performance. We consider the problem that the presence of malfunctioning or malicious sensing terminals will severely degrade the performance of cooperative spectrum sensing. In this paper, we extend the Weighted Sequential Probability Ratio Test (WSPRT) by replacing the binary local report with N-bits local report to achieve a better detection performance. Additionally, three types of reputation rating evaluation schemes are introduced: neutral, punitive and heavy punitive. Simulation results show that the extended WSPRT technique improves detection performance. Moreover, the extended WSPRT with heavy punitive scheme is shown to be the most robust against the malfunctioning or malicious sensing terminals.
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paper_title: Robust Distributed Spectrum Sensing in Cognitive Radio Networks

paper_content:

Distributed spectrum sensing (DSS) enables a Cognitive Radio (CR) network to reliably detect licensed users and avoid causing interference to licensed communications. The data fusion technique is a key component of DSS. We discuss the Byzantine failure problem in the context of data fusion, which may be caused by either malfunctioning sensing terminals or Spectrum Sensing Data Falsification (SSDF) attacks. In either case, incorrect spectrum sensing data will be reported to a data collector which can lead to the distortion of data fusion outputs. We investigate various data fusion techniques, focusing on their robustness against Byzantine failures. In contrast to existing data fusion techniques that use a fixed number of samples, we propose a new technique that uses a variable number of samples. The proposed technique, which we call Weighted Sequential Probability Ratio Test (WSPRT), introduces a reputation-based mechanism to the Sequential Probability Ratio Test (SPRT). We evaluate WSPRT by comparing it with a variety of data fusion techniques under various network operating conditions. Our simulation results indicate that WSPRT is the most robust against the Byzantine failure problem among the data fusion techniques that were considered.
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paper_title: Attack-proof collaborative spectrum sensing in cognitive radio networks

paper_content:

Collaborative sensing in cognitive radio networks can significantly improve the probability of detecting the transmission of primary users. In current collaborative sensing schemes, all collaborative secondary users are assumed to be honest. As a consequence, the system is vulnerable to attacks in which malicious secondary users report false detection results. In this paper, we investigate how to improve the security of collaborative sensing. Particularly, we develop a malicious user detection algorithm that calculates the suspicious level of secondary users based on their past reports. Then, we calculate trust values as well as consistency values that are used to eliminate the malicious users' influence on the primary user detection results. Through simulations, we show that even a single malicious user can significantly degrade the performance of collaborative sensing. The proposed trust value indicator can effectively differentiate honest and malicious secondary users. The receiver operating characteristic (ROC) curves for the primary user detection demonstrate the improvement in the security of collaborative sensing.
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paper_title: Catching Attacker(s) for Collaborative Spectrum Sensing in Cognitive Radio Systems: An Abnormality Detection Approach

paper_content:

Collaborative spectrum sensing, which collects local observations or decisions from multiple secondary users to make a decision by a fusion center, is an effective approach to alleviate the unreliability of single-user spectrum sensing. However, it is subject to the attack of malicious secondary user(s), which may send false reports. Therefore, it is necessary to detect potential attacker(s) and make attack-proof decisions for spectrum sensing. Most existing attacker detection schemes are based on the knowledge of the attacker's strategy and thus apply the Baeysian detection of attackers. However, in practical cognitive radio systems, the data fusion center typically does not know the attacker's strategy. To alleviate the problem of the unknown strategy of attacker(s), an abnormality detection approach, based on the abnormality detection in data mining, is proposed. The performance of the attacker detection in the single-attacker scenario is analyzed explicitly. For the case that the attacker does not know the reports of honest secondary users (called independent attack), it is numerically shown that attacker can always be detected as the number of spectrum sensing rounds tends to infinity. For the case that the attacker knows all the reports of other secondary users, based on which the attacker sends its report (called dependent attack), an approach for the attacker to perfectly avoid being detected is found, provided that the attacker has perfect information about the miss detection and false alarm probabilities. This motivates cognitive radio systems to protect the reports of secondary users. The performance of attacker detection in the general case of multiple attackers is demonstrated using numerical simulations.
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paper_title: Common Control Channel Security Framework for Cognitive Radio Networks

paper_content:

Cognitive radio networks are becoming an increasingly important part of the wireless networking landscape due to the ever-increasing scarcity of spectrum resources. Such networks perform co-operative spectrum sensing to find white spaces and apply policies to determine when and in which bands they may communicate. In a typical MAC protocol designed for cooperatively communicating ad hoc cognitive radio networks, nodes make use of a common control channel to perform channel negotiations before any actual data transmission. The provision of common control channel security is vital to ensure any subsequent security among the communicating cognitive radio nodes. To date, wireless security has received little attention in cognitive radio networks research. The cognitive radio paradigm introduces entirely new classes of security threats and challenges, such as selfish misbehaviours, licensed user emulation and eavesdropping. This paper presents a novel framework for providing common control channel security for co-operatively communicating cognitive radio nodes. To the best of the authors' knowledge, this is the first paper which proposes such a concept. The paper investigates how two cognitive radio nodes can authenticate each other prior to any confidential channel negotiations to ensure subsequent security against attacks. The paper also describes the importance of common control channel security and concludes with future work describing the realization of the proposed framework.
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paper_title: Secure Cognitive Networks

paper_content:

Cognitive networks are intelligent networks that can automatically sense the environment and adapt the communication parameters accordingly. These types of networks have applications in dynamic spectrum access (DSA), co-existence of different wireless networks, interference management, etc. They are thought to drive the next generation of devices, protocols and applications. Clearly, the cognitive network paradigm poses many new technical challenges in protocol design, power efficiency, spectrum management, spectrum detection, environment awareness, new distributed algorithm design, distributed spectrum measurements, QoS guarantees, and security. Overcoming these issues becomes even more challenging due to non-uniform spectrum and other radio resource allocation policies, economic considerations, the inherent transmission impairments of wireless links, and user mobility. This paper will discuss the research challenges for security in cognitive networks (CNs) [1, 2]. It will present the security, and privacy requirements, threat analysis and finally proposes a framework for security using fast authentication and authorization architecture.
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paper_title: Two Types of Attacks against Cognitive Radio Network MAC Protocols

paper_content:

Some typical MAC protocols have been proposed for multi-hop CR network recently. In a multi-hop MAC protocol, a node uses the common control channel to perform channel negotiation before data transmission. Recent research findings indicate that insecure transmission of control channels open vulnerable holes for the Denial of Service attacks. This paper makes a security analysis for CR network MAC protocols. There are two types of attacks against CR network MAC protocols. Firstly, we study how denial of service (DoS) attack is launched in multi-hop CR network MAC protocols. Then, we explore MAC layer greedy behaviors in CR networks. Our analysis and simulations indicate that such attacks can greatly affect the performance of CR networks. And the key factors for attack efficiency are presented in this paper.
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paper_title: Security in Cognitive Radio Networks: Threats and Mitigation

paper_content:

This paper describes a new class of attacks specific to cognitive radio networks. Wireless devices that can learn from their environment can also be taught things by malicious elements of their environment. By putting artificial intelligence in charge of wireless network devices, we are allowing unanticipated, emergent behavior, fitting a perhaps distorted or manipulated level of optimality. The state space for a cognitive radio is made up of a variety of learned beliefs and current sensor inputs. By manipulating radio sensor inputs, an adversary can affect the beliefs of a radio, and consequently its behavior. In this paper we focus primarily on PHY-layer issues, describing several classes of attacks and giving specific examples for dynamic spectrum access and adaptive radio scenarios. These attacks demonstrate the capabilities of an attacker who can manipulate the spectral environment when a radio is learning. The most powerful of which is a self-propagating AI virus that could interactively teach radios to become malicious. We then describe some approaches for mitigating the effectiveness of these attacks by instilling some level of "common sense" into radio systems, and requiring learned beliefs to expire and be relearned. Lastly we provide a road-map for extending these ideas to higher layers in the network stack.
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paper_title: A Proposed Propagation-Based Methodology with Which to Address the Hidden Node Problem and Security/Reliability Issues in Cognitive Radio

paper_content:

A highly accurate, fast and robust integral equation-based propagation method is presented here. It is explained how this method, in conjunction with a radio environment mapping server can be used to address the dasiahidden node problempsila and salient security/reliability issues in cognitive radio (CR) by accurately quantifying the effects or CR transmissions in realtime thus allaying the legitimate concerns of primary users regarding the deployment of CR technology. A roadmap for the development of the propagation method is given such that sufficient accuracy and execution times can be achieved.
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paper_title: Cooperative Shared Spectrum Sensing for Dynamic Cognitive Radio Networks

paper_content:

Cooperative spectrum sensing for cognitive radio networks is recently being studied to simultaneously minimize uncertainty in primary user detection and solve hidden terminal problem. Sensing wideband spectrum is another challenging task for a single cognitive radio due to large sensing time required. In this paper, we introduce a technique to tackle both wideband and cooperative spectrum sensing tasks. We divide the wideband spectrum into several subbands. Then a group of cognitive radios is assigned for sensing of a particular narrow subband. A cognitive base station is used for collecting the results and making the final decision over the full spectrum. Our proposed algorithm minimizes time and amount of energy spent for wideband spectrum scanning by a cognitive radio, and effectively detects the primary users in the wideband spectrum thanks to cooperative shared spectrum sensing.
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paper_title: Security and privacy of collaborative spectrum sensing in cognitive radio networks

paper_content:

Collaborative spectrum sensing is regarded as a promising approach to significantly improve the performance of spectrum sensing in cognitive radio networks. However, due to the open nature of wireless communications and the increasingly available software defined radio platforms, collaborative spectrum sensing also poses many new research challenges, especially in the aspect of security and privacy. In this article, we first identify the potential security threats toward collaborative spectrum sensing in CRNs. Then we review the existing proposals related to secure collaborative spectrum sensing. Furthermore, we identify several new location privacy related attacks in collaborative sensing, which are expected to compromise secondary users? location privacy by correlating their sensing reports and their physical location. To thwart these attacks, we propose a novel privacy preserving framework in collaborative spectrum sensing to prevent location privacy leaking. We design and implement a real-world testbed to evaluate the system performance. The attack experiment results show that if there is no any security guarantee, the attackers could successfully compromise a secondary user?s location privacy at a success rate of more than 90 percent. We also show that the proposed privacy preserving framework could significantly improve the location privacy of secondary users with a minimal effect on the performance of collaborative sensing.
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paper_title: Defense against Primary User Emulation Attacks in Cognitive Radio Networks

paper_content:

Cognitive radio (CR) is a promising technology that can alleviate the spectrum shortage problem by enabling unlicensed users equipped with CRs to coexist with incumbent users in licensed spectrum bands while causing no interference to incumbent communications. Spectrum sensing is one of the essential mechanisms of CRs and its operational aspects are being investigated actively. However, the security aspects of spectrum sensing have garnered little attention. In this paper, we identify a threat to spectrum sensing, which we call the primary user emulation (PUE) attack. In this attack, an adversary's CR transmits signals whose characteristics emulate those of incumbent signals. The highly flexible, software-based air interface of CRs makes such an attack possible. Our investigation shows that a PUE attack can severely interfere with the spectrum sensing process and significantly reduce the channel resources available to legitimate unlicensed users. To counter this threat, we propose a transmitter verification scheme, called LocDef (localization-based defense), which verifies whether a given signal is that of an incumbent transmitter by estimating its location and observing its signal characteristics. To estimate the location of the signal transmitter, LocDef employs a non-interactive localization scheme. Our security analysis and simulation results suggest that LocDef is effective in identifying PUE attacks under certain conditions.
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paper_title: CatchIt: Detect Malicious Nodes in Collaborative Spectrum Sensing

paper_content:

Collaborative spectrum sensing in cognitive radio networks has been proposed as an efficient way to improve the performance of primary users detection. In collaborative spectrum sensing schemes, secondary users are often assumed to be trustworthy. In practice, however, cognitive radio nodes can be compromised. Compromised secondary users can report false detection results and significantly degrade the performance of spectrum sensing. In this paper, we investigate the case that there are multiple malicious users in cognitive radio networks and the exact number of malicious users is unknown. An onion-peeling approach is proposed to defense against multiple untrustworthy secondary nodes. We calculate suspicious level of all nodes according to their reports. When the suspicious level of a node is beyond certain threshold, it will be considered as malicious and its report will be excluded in decision-making. We continue to calculate the suspicious level of remaining nodes until no malicious node can be found. Simulation results show that malicious nodes greatly degrade the performance of collaborative sensing, and the proposed scheme can efficiently detect malicious nodes. Compared with existing defense methods, the proposed scheme significantly improves the performance of primary user detection, measured by ROC curves, and captures the dynamic change in the behaviors of malicious users.
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paper_title: Achieving cooperative spectrum sensing in wireless cognitive radio networks

paper_content:

Dynamic spectrum access has been studied to exploit instantaneous spectrum availability by opening licensed spectrum to secondary users. To achieve high spectrum efficiency, secondary unlicensed users need to continuously sense spectrum to detect the presence of primary licensed users. Cooperative spectrum sensing has been recognized as a powerful solution to improve spectrum sensing performance, which requires nearby wireless nodes to share sensing results with each other. However, information sharing is achieved through broadcasting in wireless networks, which can provide free-riding opportunity for selfish nodes. Selfish nodes can benefit from receiving the sensing results from its neighbors by free without sharing. Therefore, appropriate strategies are essential to enforce and sustain the cooperation among neighboring nodes. In this paper we model cooperative spectrum sensing as an N-player horizontal infinite game, and study varies strategies for it. In wireless networks, the frequently occurred collisions make the cooperation enforcement problem quite challenging as it is hard to tell whether the information lost is due to nodes' selfishness or wireless collision. In this paper, we prove that Grim Trigger strategy, a classical strategy to stimulate cooperation in an infinite game, can result in poor performance due to random errors. We then propose a strategy basing on Carrot-and-Stick strategy, which can recover cooperation among multiple players from deviation. We prove that if nodes are sufficiently far-sight, or equivalently the entire system runs sufficiently long, the Nash Equilibrium of the proposed strategy for spectrum sensing game is still mutual cooperation, even under collision situation. We also prove that the proposed strategy is robust to collisions and colluding cheat.
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paper_title: Evolutionary cooperative spectrum sensing game: how to collaborate?

paper_content:

Cooperative spectrum sensing has been shown to be able to greatly improve the sensing performance in cognitive radio networks. However, if cognitive users belong to different service providers, they tend to contribute less in sensing in order to increase their own throughput. In this paper, we propose an evolutionary game framework to answer the question of "how to collaborate" in multiuser de-centralized cooperative spectrum sensing, because evolutionary game theory provides an excellent means to address the strategic uncertainty that a user/player may face by exploring different actions, adaptively learning during the strategic interactions, and approaching the best response strategy under changing conditions and environments using replicator dynamics. We derive the behavior dynamics and the evolutionarily stable strategy (ESS) of the secondary users. We then prove that the dynamics converge to the ESS, which renders the possibility of a de-centralized implementation of the proposed sensing game. According to the dynamics, we further develop a distributed learning algorithm so that the secondary users approach the ESS solely based on their own payoff observations. Simulation results show that the average throughput achieved in the proposed cooperative sensing game is higher than the case where secondary users sense the primary user individually without cooperation. The proposed game is demonstrated to converge to the ESS, and achieve a higher system throughput than the fully cooperative scenario, where all users contribute to sensing in every time slot.
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paper_title: Authenticating Primary Users' Signals in Cognitive Radio Networks via Integrated Cryptographic and Wireless Link Signatures

paper_content:

To address the increasing demand for wireless bandwidth, cognitive radio networks (CRNs) have been proposed to increase the efficiency of channel utilization; they enable the sharing of channels among secondary (unlicensed) and primary (licensed) users on a non-interference basis. A secondary user in a CRN should constantly monitor for the presence of a primary user's signal to avoid interfering with the primary user. However, to gain unfair share of radio channels, an attacker (e.g., a selfish secondary user) may mimic a primary user's signal to evict other secondary users. Therefore, a secure primary user detection method that can distinguish a primary user's signal from an attacker's signal is needed. A unique challenge in addressing this problem is that Federal Communications Commission (FCC) prohibits any modification to primary users. Consequently, existing cryptographic techniques cannot be used directly. In this paper, we develop a novel approach for authenticating primary users' signals in CRNs, which conforms to FCC's requirement. Our approach integrates cryptographic signatures and wireless link signatures (derived from physical radio channel characteristics) to enable primary user detection in the presence of attackers. Essential to our approach is a {\em helper node} placed physically close to a primary user. The helper node serves as a "bridge" to enable a secondary user to verify cryptographic signatures carried by the helper node's signals and then obtain the helper node's authentic link signatures to verify the primary user's signals. A key contribution in our paper is a novel physical layer authentication technique that enables the helper node to authenticate signals from its associated primary user. Unlike previous techniques for link signatures, our approach explores the geographical proximity of the helper node to the primary user, and thus does not require any training process.
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paper_title: Using Classification to Protect the Integrity of Spectrum Measurements in White Space Networks

paper_content:

The emerging paradigm for using the wireless spectrum more efficiently is based on enabling secondary users to exploit white-space frequencies that are not occupied by primary users. A key enabling technology for forming networks over white spaces is distributed spectrum measurements to identify and assess the quality of unused channels. This spectrum availability data is often aggregated at a central base station or database to govern the usage of spectrum. This process is vulnerable to integrity violations if the devices are malicious and misreport spectrum sensing results. In this paper we propose CUSP, a new technique based on machine learning that uses a trusted initial set of signal propagation data in a region as input to build a classifier using Support Vector Machines. The classifier is subsequently used to detect integrity violations. Using classification eliminates the need for arbitrary assumptions about signal propagation models and parameters or thresholds in favor of direct training data. Extensive evaluations using TV transmitter data from the FCC, terrain data from NASA, and house density data from the US Census Bureau for areas in Illinois and Pennsylvania show that our technique is effective against attackers of varying sophistication, while accommodating for regional terrain and shadowing diversity. 1
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paper_title: Double Thresholds Based Cooperative Spectrum Sensing Against Untrusted Secondary Users in Cognitive Radio Networks

paper_content:

Spectrum sensing is an essential mechanism in a cognitive radio network. However, the detection performance will be greatly degraded when few untrusted secondary users exist which can be identified as 'Always Yes' users and 'Always No' users. In this paper, we propose an energy detector with double thresholds combined with revised data fusion rules to find these untrusted users and counteract their malicious effects. Probabilities of detection and false alarm of three kinds of revised data fusion rules are derived. Compared with the conventional cooperative methods, our method can get a better detection performance.
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paper_title: Secure Cooperative Sensing Techniques for Cognitive Radio Systems

paper_content:

The most important task for a cognitive radio (CR) system is to identify the primary licensed users over a wide range of spectrum. Cooperation among spectrum sensing devices has been shown to offer various benefits including decrease in sensitivity requirements of the individual sensing devices. However, it has been shown in the literature that the performance of cooperative sensing schemes can be severely degraded due to presence of malicious users sending false sensing data. In this paper, we present techniques to identify such malicious users and mitigate their harmful effect on the performance of the cooperative sensing system.
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paper_title: An Efficient, Secure and User Privacy-Preserving Search Protocol for Peer-to-Peer Networks

paper_content:

A peer-to-peer (P2P) network is a distributed system in which the autonomous peers can leave and join the network at their will and share their resources to perform some functions in a distributed manner. In an unstructured P2P network, there is no centralized administrative entity that controls the operations of the peers, and the resources (i.e., the files) that the peers share are not related to the their topological positions in the network. With the advent of the Internet of Things (IoT), the P2P networks have found increased interest in the research community since the search protocols for these networks can be gainfully utilized in the resource discovery process for the IoT applications. However, there are several challenges in designing an efficient search protocol for the unstructured P2P networks since these networks suffer from problems such as fake content distribution, free riding, whitewashing, poor search scalability, lack of a robust trust model and the absence a of user privacy protection mechanism. Moreover, the peers can join and leave the network frequently, which makes trust management and searching in these networks quite a challenging task. In this chapter, a secure and efficient searching protocol for unstructured P2P networks is proposed that utilizes topology adaptation by constructing an overlay of trusted peers and increases the search efficiency by intelligently exploiting the formation of semantic community structures among the trustworthy peers. It also guarantees that the privacy of the users and data in the network is protected. Extensive simulation results are presented and the performance of the protocol is also compared with those of some of the existing protocols to demonstrate its advantages.
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paper_title: The Research of Cross-Layer Architecture Design and Security for Cognitive Radio Network

paper_content:

In this paper, we discuss the framework of cognitive radio network, analysis motivations for cross-layer design and security in cognitive radio network (CRN) first. Secondly, we proposed a novel architecture in which the dynamic channel access is achieved by a cross-layer design between the PHY and MAC layers for cognitive radio network. Moreover the resolution of cross-layer security problem is proposed and analysis in mathematic. Finally, we discuss the security issues of spectrum sensing for Centralized CRN and a novel centralized dynamic channel access mechanism is proposed, simulation shows it can improve network performance.
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paper_title: CatchIt: Detect Malicious Nodes in Collaborative Spectrum Sensing

paper_content:

Collaborative spectrum sensing in cognitive radio networks has been proposed as an efficient way to improve the performance of primary users detection. In collaborative spectrum sensing schemes, secondary users are often assumed to be trustworthy. In practice, however, cognitive radio nodes can be compromised. Compromised secondary users can report false detection results and significantly degrade the performance of spectrum sensing. In this paper, we investigate the case that there are multiple malicious users in cognitive radio networks and the exact number of malicious users is unknown. An onion-peeling approach is proposed to defense against multiple untrustworthy secondary nodes. We calculate suspicious level of all nodes according to their reports. When the suspicious level of a node is beyond certain threshold, it will be considered as malicious and its report will be excluded in decision-making. We continue to calculate the suspicious level of remaining nodes until no malicious node can be found. Simulation results show that malicious nodes greatly degrade the performance of collaborative sensing, and the proposed scheme can efficiently detect malicious nodes. Compared with existing defense methods, the proposed scheme significantly improves the performance of primary user detection, measured by ROC curves, and captures the dynamic change in the behaviors of malicious users.
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paper_title: Reputation-based cooperative spectrum sensing with trusted nodes assistance

paper_content:

Existing cooperative spectrum sensing (CSS) schemes are typically vulnerable to attacks where misbehaved cognitive radios (CRs) falsify sensing data. To ensure the robustness of spectrum sensing, this letter presents a secure CSS scheme by introducing a reputation-based mechanism to identify misbehaviors and mitigate their harmful effect on sensing performance. Encouraged by the fact that such secure CSS is sensitive to the correctness of reputations, we further present a trusted node assistance scheme. This scheme starts with reliable CRs. Sensing information from other CRs are incorporated into cooperative sensing only when their reputation is verified, which increases robustness of cooperative sensing. Simulations verify the effectiveness of the proposed schemes.
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paper_title: Defense against spectrum sensing data falsification attacks in mobile ad hoc networks with cognitive radios

paper_content:

Cognitive radios (CRs) have been considered for use in mobile ad hoc networks (MANETs). The area of security in Cognitive Radio MANETs (CR-MANETs) has yet to receive much attention. However, some distinct characteristics of CRs introduce new, non-trivial security risks to CR-MANETs. In this paper, we study spectrum sensing data falsification (SSDF) attacks to CR-MANETs, in which intruders send false local spectrum sensing results in cooperative spectrum sensing, and SSDF may result in incorrect spectrum sensing decisions by CRs. We present a consensus-based cooperative spectrum sensing scheme to counter SSDF attacks in CR-MANETs. Our scheme is based on recent advances in consensus algorithms that have taken inspiration from self-organizing behavior of animal groups such as fish. Unlike the existing schemes, there is no need for a common receiver to do the data fusion for reaching the final decision to counter SSDF attacks. Simulation results are presented to show the effectiveness of the proposed scheme.
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paper_title: Catching Attacker(s) for Collaborative Spectrum Sensing in Cognitive Radio Systems: An Abnormality Detection Approach

paper_content:

Collaborative spectrum sensing, which collects local observations or decisions from multiple secondary users to make a decision by a fusion center, is an effective approach to alleviate the unreliability of single-user spectrum sensing. However, it is subject to the attack of malicious secondary user(s), which may send false reports. Therefore, it is necessary to detect potential attacker(s) and make attack-proof decisions for spectrum sensing. Most existing attacker detection schemes are based on the knowledge of the attacker's strategy and thus apply the Baeysian detection of attackers. However, in practical cognitive radio systems, the data fusion center typically does not know the attacker's strategy. To alleviate the problem of the unknown strategy of attacker(s), an abnormality detection approach, based on the abnormality detection in data mining, is proposed. The performance of the attacker detection in the single-attacker scenario is analyzed explicitly. For the case that the attacker does not know the reports of honest secondary users (called independent attack), it is numerically shown that attacker can always be detected as the number of spectrum sensing rounds tends to infinity. For the case that the attacker knows all the reports of other secondary users, based on which the attacker sends its report (called dependent attack), an approach for the attacker to perfectly avoid being detected is found, provided that the attacker has perfect information about the miss detection and false alarm probabilities. This motivates cognitive radio systems to protect the reports of secondary users. The performance of attacker detection in the general case of multiple attackers is demonstrated using numerical simulations.
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paper_title: Cooperative Spectrum Sensing with Double Threshold Detection Based on Reputation in Cognitive Radio

paper_content:

Cooperative spectrum sensing can mitigate the effects of shadowing and fading. However, when the number of cognitive users is very large, the bandwidth for reporting their sensing results will be insufficient. In order to eliminate the fail sensing problem for a cognitive radio system with double threshold detector, a new cooperative spectrum sensing algorithm is presented based on reputation in this paper. In particular, the closed forms for the normalized average number of sensing bits, the probabilities of the detection and the false-alarm are derived. Simulation results show that the average number of sensing bits decreases greatly without failing sensing, and the sensing performance is improved comparing with the conventional double threshold detection and the conventional single threshold detection.
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paper_title: Reputation- and Trust-Based Systems for Wireless Self-organizing Networks

paper_content:

Traditional approach of providing network security has been to borrow tools and mechanisms from cryptography. However, the conventional view of security based on cryptography alone is not sufficient for the defending against unique and novel types of misbehavior exhibited by nodes in wireless self-organizing networks such as mobile ad hoc networks and wireless sensor networks. Reputation-based frameworks, where nodes maintain reputation of other nodes and use it to evaluate their trustworthiness, are deployed to provide scalable, diverse and a generalized approach for countering different types of misbehavior resulting form malicious and selfish nodes in these networks. In this chapter, we present a comprehensive discussion on reputation and trust-based systems for wireless self-organizing networks. Different classes of reputation system are described along with their unique characteristics and working principles. A number of currently used reputation systems are critically reviewed and compared with respect to their effectiveness and efficiency of performance. Some open problems in the area of reputation and trust-based system within the domain of wireless self-organizing networks are also discussed.
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paper_title: Robust Distributed Spectrum Sensing in Cognitive Radio Networks

paper_content:

Distributed spectrum sensing (DSS) enables a Cognitive Radio (CR) network to reliably detect licensed users and avoid causing interference to licensed communications. The data fusion technique is a key component of DSS. We discuss the Byzantine failure problem in the context of data fusion, which may be caused by either malfunctioning sensing terminals or Spectrum Sensing Data Falsification (SSDF) attacks. In either case, incorrect spectrum sensing data will be reported to a data collector which can lead to the distortion of data fusion outputs. We investigate various data fusion techniques, focusing on their robustness against Byzantine failures. In contrast to existing data fusion techniques that use a fixed number of samples, we propose a new technique that uses a variable number of samples. The proposed technique, which we call Weighted Sequential Probability Ratio Test (WSPRT), introduces a reputation-based mechanism to the Sequential Probability Ratio Test (SPRT). We evaluate WSPRT by comparing it with a variety of data fusion techniques under various network operating conditions. Our simulation results indicate that WSPRT is the most robust against the Byzantine failure problem among the data fusion techniques that were considered.
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paper_title: Attack-proof collaborative spectrum sensing in cognitive radio networks

paper_content:

Collaborative sensing in cognitive radio networks can significantly improve the probability of detecting the transmission of primary users. In current collaborative sensing schemes, all collaborative secondary users are assumed to be honest. As a consequence, the system is vulnerable to attacks in which malicious secondary users report false detection results. In this paper, we investigate how to improve the security of collaborative sensing. Particularly, we develop a malicious user detection algorithm that calculates the suspicious level of secondary users based on their past reports. Then, we calculate trust values as well as consistency values that are used to eliminate the malicious users' influence on the primary user detection results. Through simulations, we show that even a single malicious user can significantly degrade the performance of collaborative sensing. The proposed trust value indicator can effectively differentiate honest and malicious secondary users. The receiver operating characteristic (ROC) curves for the primary user detection demonstrate the improvement in the security of collaborative sensing.
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paper_title: Collaborative Spectrum Sensing in the Presence of Byzantine Attacks in Cognitive Radio Networks

paper_content:

Cognitive radio (CR) has emerged as a solution to the problem of spectrum scarcity as it exploits the transmission opportunities in the under-utilized spectrum bands of primary users. Collaborative (or distributed) spectrum sensing has been shown to have various advantages in terms of spectrum utilization and robustness. The data fusion scheme is a key component of collaborative spectrum sensing. In this paper, we analyze the performance limits of collaborative spectrum sensing under Byzantine Attacks where malicious users send false sensing data to the fusion center leading to increased probability of incorrect sensing results. We show that above a certain fraction of Byzantine attackers in the CR network, data fusion scheme becomes completely incapable and no reputation based fusion scheme can achieve any performance gain. We present optimal attacking strategies for given attacking resources and also analyze the possible counter measures at the fusion center (FC).
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paper_title: A survey of spectrum sensing algorithms for cognitive radio applications

paper_content:

The spectrum sensing problem has gained new aspects with cognitive radio and opportunistic spectrum access concepts. It is one of the most challenging issues in cognitive radio systems. In this paper, a survey of spectrum sensing methodologies for cognitive radio is presented. Various aspects of spectrum sensing problem are studied from a cognitive radio perspective and multi-dimensional spectrum sensing concept is introduced. Challenges associated with spectrum sensing are given and enabling spectrum sensing methods are reviewed. The paper explains the cooperative sensing concept and its various forms. External sensing algorithms and other alternative sensing methods are discussed. Furthermore, statistical modeling of network traffic and utilization of these models for prediction of primary user behavior is studied. Finally, sensing features of some current wireless standards are given.
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paper_title: Security threats to signal classifiers using self-organizing maps

paper_content:

Spectrum sensing is required for many cognitive radio applications, including spectral awareness, interoperability, and dynamic spectrum access. Previous work has demonstrated the ill effects of primary user emulation attacks, and pointed out specific vulnerabilities in spectrum sensing that uses featurebased classifiers. This paper looks specifically at the use of unsupervised learning in signal classifiers, and attacks against self-organizing maps. By temporarily manipulating their signals, attackers can cause other secondary users to permanently misclassify them as primary users, giving them complete access to the spectrum. In the paper we develop the theory behind manipulating the decision regions in a neural network using self-organizing maps. We then demonstrate through simulation the ability for an attacker to formulate the necessary input signals to execute the attack. Lastly we provide recommendations to mitigate the efficacy of this type of attack.
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paper_title: Ensuring Trustworthy Spectrum Sensing in Cognitive Radio Networks

paper_content:

Cognitive Radio (CR) is a promising technology that can alleviate the spectrum shortage problem by enabling unlicensed users equipped with CRs to coexist with incumbent users in licensed spectrum bands without inducing interference to incumbent communications. Spectrum sensing is one of the essential mechanisms of CRs that has attracted great attention from researhers recently. Although the operational aspects of spectrum sensing are being investigated actively, its security aspects have garnered little attention. In this paper, we describe an attack that poses a great threat to spectrum sensing. In this attack, which is called the primary user emulation (PUE) attack, an adversary's CR transmits signals whose characteristics emulate those of incumbent signals. The highly flexible, software-based air interface of CRs makes such an attack possible. Our investigation shows that a PUE attack can severely interfere with the spectrum sensing process and significantly reduce the channel resources available to legitimate unlicensed users. As a way of countering this threat, we propose a transmitter verification procedure that can be integrated into the spectrum sensing mechanism. The transmitter verification procedure employs a location verification scheme to distinguish incumbent signals from unlicensed signals masquerading as incumbent signals. Two alternative techniques are proposed to realize location verification: Distance Ratio Test and Distance Difference Test. We provide simulation results of the two techniques as well as analyses of their security in the paper.
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paper_title: A New Cooperative Detection Technique with Malicious User Suppression

paper_content:

Spectrum detection for vacant bands is one of the key techniques in cognitive radio (CR) systems. Cooperative detection outperforms single user detection in many aspects. The existence of malicious user could severely degrade the performance of cooperative CR systems. In this paper, a new cooperative detection scheme with malicious user suppression is proposed, which has lower complexity and better performance compared with the existing one. Simulation results show that when 25% users in the system are malicious, our proposed method can introduce more improvement of missed detection probability by nearly 20%.
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paper_title: A PHY-layer Authentication Approach for Transmitter Identification in Cognitive Radio Networks

paper_content:

Cognitive radio (CR) was proposed as the key technologies to achieve the secondary usage of the spectrum. The security problems of CR networks have not been intensively studied, such as the primary user emulation (PUE) attacks. In this paper, we study the non-interactive security issues for wireless networks and propose a physical layer authentication approach to prevent PUE attacks in CR networks. We extract transmitter location fingerprints from the wireless medium in the multipath propagation environment. Wavelet transform is used to extract the characteristics of these fingerprints. Simulation and experiment results show that our approach can identify the PUE attackers and the legitimate primary users effectively.
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paper_title: On Secure Spectrum Sensing in Cognitive Radio Networks Using Emitters Electromagnetic Signature

paper_content:

As Cognitive Radio Network (CRN) emerges as an extremely promising next generation wireless technology that can ease the apparent spectrum scarcity and support novel wireless applications; they will become bigger targets for hackers. Moreover, they will also be exposed to diverse security threats especially at the physical layer (PHY) spectrum sensing module. Hence, security consideration is central in its development. Starting with overview of on-going research efforts in CR-based network security, this paper describes a PHY attacker model that exploits the adaptability and flexibility of CRN. In thwarting this attack, we propose a waveform pattern recognition scheme to identify emitters and detect camouflaging attackers by using the Electromagnetic Signature (EMS) of the transceiver. On the performance of the technique, our simulation results show that our approach is effective for spectrum monitoring, mitigating denial-of-service threats and facilitating spectral efficiency.
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paper_title: Towards Secure Spectrum Decision

paper_content:

The key idea of dynamic spectrum access (DSA) networks is to allow the secondary, unlicensed users to detect and use unused portions of the spectrum (white spaces) opportunistically. The two main constraints in the design of DSA networks is to make sure that this opportunistic access is done without any disruption of service to the primary users and without any modifications to the primaries themselves. Most architectures and protocols for DSA networks in the literature assume that all parties are honest and that there are no attackers. Recently (IEEE ICC, CogNet 2008) we demonstrated the failure of this approach by showing that an attacker can manipulate messages to convince the parties involved in the protocol to make incorrect spectrum decisions. In this paper, we consider spectrum decision protocols in clustered infrastructure-based dynamic spectrum access networks where the spectrum decision in each cluster is coordinated by some central authority. We propose an efficient and provably secure protocol that can be used to protect the spectrum decision process against a malicious adversary.
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paper_title: Self-Organized Public-Key Management for Mobile Ad Hoc Networks

paper_content:

In contrast with conventional networks, mobile ad hoc networks usually do not provide online access to trusted authorities or to centralized servers, and they exhibit frequent partitioning due to link and node failures and to node mobility. For these reasons, traditional security solutions that require online trusted authorities or certificate repositories are not well-suited for securing ad hoc networks. We propose a fully self-organized public-key management system that allows users to generate their public-private key pairs, to issue certificates, and to perform authentication regardless of the network partitions and without any centralized services. Furthermore, our approach does not require any trusted authority, not even in the system initialization phase.
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paper_title: A Radio-independent Authentication Protocol (EAP-CRP) for Networks of Cognitive Radios

paper_content:

Securing future wireless networks will be a critical challenge as the popularity of mobile communications implies that wireless networks will be the target of abuse. The next generation of wireless networks, as envisioned by recent advances in cognitive radio (CR) technologies, will be autonomic and able to adjust their configuration to changes in the communication environment. Unfortunately, the authentication frameworks for various radio technologies, such as IEEE802.11 and 802.16, are quite different from one another and, in order to support radio reconfiguration, it is necessary to devise an appropriate authentication framework for CR systems. In this paper, we propose a radio-independent authentication protocol for CRs that is independent of the underlying radio protocols and able to support EAP transport. The re-keying protocol assumes user-specific information, such as location information, as a key seed. The keys for authentication and encryption are derived from the historical location registry of a mobile terminal. The keys are frequently updated as mobile users' position varies. After discussing authentication issues for CR networks, radio-independent authentication via location information, and application to EAP transport, we evaluate the confidentiality of the key management method and its integration with EAP, thereby supporting the effectiveness of our key management method for CR networks.
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paper_title: Common Control Channel Security Framework for Cognitive Radio Networks

paper_content:

Cognitive radio networks are becoming an increasingly important part of the wireless networking landscape due to the ever-increasing scarcity of spectrum resources. Such networks perform co-operative spectrum sensing to find white spaces and apply policies to determine when and in which bands they may communicate. In a typical MAC protocol designed for cooperatively communicating ad hoc cognitive radio networks, nodes make use of a common control channel to perform channel negotiations before any actual data transmission. The provision of common control channel security is vital to ensure any subsequent security among the communicating cognitive radio nodes. To date, wireless security has received little attention in cognitive radio networks research. The cognitive radio paradigm introduces entirely new classes of security threats and challenges, such as selfish misbehaviours, licensed user emulation and eavesdropping. This paper presents a novel framework for providing common control channel security for co-operatively communicating cognitive radio nodes. To the best of the authors' knowledge, this is the first paper which proposes such a concept. The paper investigates how two cognitive radio nodes can authenticate each other prior to any confidential channel negotiations to ensure subsequent security against attacks. The paper also describes the importance of common control channel security and concludes with future work describing the realization of the proposed framework.
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paper_title: Spectrum Enforcement and Liability Assignment in Cognitive Radio Systems

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The advent of frequency-agile radios holds the potential for improving the utilization of spectrum by allowing wireless systems to dynamically adapt their spectral footprint based on the local conditions. Whether this is done using market mechanisms or opportunistic approaches, the gains result from shifting some responsibility for avoiding harmful interference from the static "regulatory layer" to layers that can adapt at runtime. However, this leaves open the major problem of how to enforce/incentivize compliance and what the structure of "light-handed" regulation should be. This paper examines this and focuses on two specific technical problems: (a) determining whether harmful interference is occurring and (b) assigning liability by detecting the culprits. "Light-handed regulation" is interpreted as making unambiguous (and easily certified) requirements on the behavior of individual devices themselves while still preserving significant freedom to innovate at both the device and the system level. The basic idea explored here is to require the PHY/MAC layers of a cognitive radio to guarantee silence during certain time- slots where the exact sequence of required silences is given by a device/system -specific code. Thus, if a system is a source of harmful interference, the interference pattern itself contains the signature of the culprit. Nevertheless, identifying the unique interference pattern becomes challenging as both the number of cognitive radios and the number of harmful interferers increases. The key tradeoffs are explored in terms of the "regulatory overhead" (amount of enforced silence) needed to make guarantees. The quality of regulatory guarantees is expressed by the time required to convict the guilty, the number of potential cognitive systems that can be supported, and the number of simultaneously guilty parties that can be resolved. We show that the time to conviction need only scale logarithmically in the potential number of cognitive users. The base of the logarithm is determined by the amount of overhead that we will tolerate and how many guilty parties we want to be able to resolve.
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paper_title: Policy-based spectrum access control for dynamic spectrum access network radios

paper_content:

We describe the design of a policy-based spectrum access control system for the Defense Advanced Research Projects Agency (DARPA) NeXt Generation (XG) communications program to overcome harmful interference caused by a malfunctioning device or a malicious user. In tandem with signal-detection-based interference-avoidance algorithms employed by cognitive software-defined radios (SDR), we design a set of policy-based components, tightly integrated with the accredited kernel on the radio device. The policy conformance and enforcement components ensure that a radio does not violate machine understandable policies, which are encoded in a declarative language and which define stakeholders' goals and requirements. We report on our framework experimentation, illustrating the capability offered to radios for enforcing policies and the capability for managing radios and securing access control to interfaces changing the radios' policies.
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paper_title: TRIESTE: A Trusted Radio Infrastructure for Enforcing SpecTrum Etiquettes

paper_content:

There has been considerable effort directed at developing "cognitive radio" (CR) platforms, which will expose the lower-layers of the protocol stack to researchers, developers and the "public". In spite of the great potential of such a radio platform, such "public" development threatens the success of these platforms: the proliferation of such wireless platforms, plus the open-source nature of their supporting software, is powerful but also dangerous. It is easily conceivable that inexpensive and widely available cognitive radios could become an ideal platform for abuse since the lowest layers of the wireless protocol stack are accessible to programmers. In order to regulate the future radio environment, this paper presents a framework, known as TRIESTE (Trusted Radio Infrastructure for Enforcing SpecTrum Etiquettes), which can ensure that radio devices are only able to access/use the spectrum in a manner that conforms to their privileges. In TRIESTE, two levels of etiquette enforcement mechanisms are employed. The first is an on-board mechanism that ensures trustworthy radio operation by restricting any potential violation operation from accessing the radio through a secure component located in each CR. External to individual cognitive radios, an infrastructure consisting of spectrum sensors monitors the radio environment, and reports measurements to spectrum police agents that punish CRs if violations are detected.
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paper_title: Secure Physical Layer using Dynamic Permutations in Cognitive OFDMA Systems

paper_content:

This paper proposes a novel lightweight mechanism for a secure physical (PHY) layer in cognitive radio network (CRN) using orthogonal frequency division multiplexing (OFDM). User's data symbols are mapped over the physical subcarriers with a permutation formula. The PHY layer is secured with a random and dynamic subcarrier permutation which is based on a single pre-shared information and depends on dynamic spectrum access (DSA). The dynamic subcarrier permutation is varying over time, geographical location and environment status, resulting in a very robust protection that ensures confidentiality. The method is shown to be effective also for existing non-cognitive systems. The proposed mechanism is effective against eavesdropping even if the eavesdropper adopts a long-time patterns analysis, thus protecting cryptography techniques of higher layers. The correlation properties of the permutations are analyzed for several DSA patterns. Simulations are performed according to the parameters of the IEEE 802.16e system model. The securing mechanism proposed provides intrinsic PHY layer security and it can be easily implemented in the current IEEE 802.16 standard applying almost negligible modifications.
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paper_title: Anti-jamming coding techniques with application to cognitive radio

paper_content:

In this paper, we consider the design of efficient anti-jamming coding techniques for recovering lost packets transmitted through parallel channels. We present two coding schemes with small overhead and low complexity, namely, rateless coding and piecewise coding. For piecewise coding, we propose the optimal as well as several suboptimal design methods to build short block codes with small number of parity checks. One application of the anti-jamming coding techniques is in a cognitive radio system to protect the secondary users from the interference by the primary users. For such application, we consider two types of subchannel selections, i.e., the single uniform and general non-uniform subchannel selections. Throughput and the goodput performance of the secondary users employing either anti-jamming coding technique is analyzed under both subchannel selection strategies. The results show that both coding techniques provide reliable transmissions with high throughput and small redundancy. The piecewise coding using the designed short codes provides better performance with smaller overhead under low to medium jamming rate. For non-uniform subchannel selection, the designed short code improves the throughput and goodput performance of secondary transmission with antijamming piecewise coding while the rateless coding provides similar or worse performance than that in the uniform case.
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paper_title: Considerations for Successful Cognitive Radio Systems in US TV White Space

paper_content:

On February 17, 2009, the United States will complete the transition to digital television. The FCC is in the process of establishing rules to allow unlicensed secondary use of the TV "white space" that this transition creates. This television white space (TVWS) opens vital new portions of limited radio spectrum and enables delivery of new communication services, particularly wireless broadband, to millions of underserved Americans. In some rural markets, up to 250 MHz of spectrum could be utilized. Expected initial system deployments in TVWS include wireless Internet service providers (WISPs) and broadband coverage systems for business enterprises. It is critical that these early services are successful, both technically in protecting incumbent licensed users as well as financially in being commercially viable. Cognitive radio technologies are available that enable radio systems operating in the TVWS spectrum to reliably protect the incumbent licensed users. These technologies include geolocation, augmented by sensing, and beaconing. Existing protocols, such as WiMax, WiFi, and proprietary protocols, rebanded to the UHF frequency ranges, will provide broadband data throughput at adequate ranges to allow practical services. It is important to develop and deploy early viable solutions into this band that protect incumbent licensed users so that cycles of learning can start. Lessons from these early systems will allow the industry to accept more aggressive cognitive radio technologies and services, will offer greater comfort to critics of the technology, and will provide regulatory agencies worldwide with data for future rulemaking.
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paper_title: Radio-telepathy: extracting a secret key from an unauthenticated wireless channel

paper_content:

Securing communications requires the establishment of cryptographic keys, which is challenging in mobile scenarios where a key management infrastructure is not always present. In this paper, we present a protocol that allows two users to establish a common cryptographic key by exploiting special properties of the wireless channel: the underlying channel response between any two parties is unique and decorrelates rapidly in space. The established key can then be used to support security services (such as encryption) between two users. Our algorithm uses level-crossings and quantization to extract bits from correlated stochastic processes. The resulting protocol resists cryptanalysis by an eavesdropping adversary and a spoofing attack by an active adversary without requiring an authenticated channel, as is typically assumed in prior information-theoretic key establishment schemes. We evaluate our algorithm through theoretical and numerical studies, and provide validation through two complementary experimental studies. First, we use an 802.11 development platform with customized logic that extracts raw channel impulse response data from the preamble of a format-compliant 802.11a packet. We show that it is possible to practically achieve key establishment rates of ~ 1 bit/sec in a real, indoor wireless environment. To illustrate the generality of our method, we show that our approach is equally applicable to per-packet coarse signal strength measurements using off-the-shelf 802.11 hardware.
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Title: A Survey on Security and Privacy Protocols for Cognitive Wireless Sensor Networks

Section 1: Introduction
Description 1: Discuss the significance of Wireless Sensor Networks (WSNs) and Cognitive Wireless Sensor Networks (CWSNs), their applications, benefits, and the necessity for security protocols.

Section 2: Security and Privacy Issues in WSNs
Description 2: Cover the traditional security and privacy challenges in WSNs, including specific types of attacks such as DoS, secrecy, authentication threats, and stealthy attacks on service integrity.

Section 3: Security Mechanisms in Traditional WSNs
Description 3: Present various security mechanisms employed in traditional WSNs, such as cryptographic applications, key management protocols, defense mechanisms against DoS attacks, and secure data aggregation.

Section 4: Security Vulnerabilities in CWSNs
Description 4: Outline the additional security vulnerabilities introduced in CWSNs, focusing on threats unique to cognitive radio functionalities, including masquerading, jamming, unauthorized spectrum access, and attacks on the cognitive engine.

Section 5: Work on Identification of CWSN Threats
Description 5: Provide an overview of research identifying specific attacks on CR networks, including jamming, PUE attacks, masquerading attacks, false spectrum reports by secondary users, and cognitive control channel security.

Section 6: Security Mechanisms for CWSNs
Description 6: Detail various defense mechanisms specific to CWSNs, enhancing sensor inputs, using reputation-based systems, robust authentication schemes, prevention of unauthorized spectrum access, and protection frameworks for CCCs.

Section 7: Emerging Research Directions
Description 7: Identify and discuss potential future research challenges and directions in the field of cognitive radio networks, particularly focusing on security and privacy issues that need addressing for real-world deployment.

Section 8: Conclusion
Description 8: Summarize the presented security threats and defense mechanisms for CWSNs and underline the importance of addressing these security challenges for the successful deployment of cognitive wireless sensor networks.