Multimedia Security: A Survey of Chaos-Based Encryption Technology
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paper_title: Efficient image or video encryption based on spatiotemporal chaos system

paper_content:

Abstract In this paper, an efficient image/video encryption scheme is constructed based on spatiotemporal chaos system. The chaotic lattices are used to generate pseudorandom sequences and then encrypt image blocks one by one. By iterating chaotic maps for certain times, the generated pseudorandom sequences obtain high initial-value sensitivity and good randomness. The pseudorandom-bits in each lattice are used to encrypt the Direct Current coefficient (DC) and the signs of the Alternating Current coefficients (ACs). Theoretical analysis and experimental results show that the scheme has good cryptographic security and perceptual security, and it does not affect the compression efficiency apparently. These properties make the scheme a suitable choice for practical applications.
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paper_title: Cryptography based on chaotic systems

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In this letter, a new chaos-based secure communication scheme is proposed in an attempt to thwart the attacks proposed recently. Instead of encoding the message signal in a chaotic system directly, we use two chaotic signals in our scheme. One of the chaotic signals is used to synchronize the chaotic encrypter and the chaotic decrypter. The other is used to encrypt the plain signal by using a multishift cipher scheme. Thus the transmitted signal is not used to encrypt the message and a more complicated method of encryption is used.
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paper_title: Cryptanalysis and Improvement of a Block Cipher Based on Multiple Chaotic Systems

paper_content:

Wang and Yu proposed a block cipher scheme based on dynamic sequences generated ::: by multiple chaotic systems, which overcomes the problem of periodical degradation on ::: random sequences due to computational precision. Their scheme has a feature that a ::: plaintext is encrypted by a keystream created from several one-dimensional chaotic maps. ::: However, this feature results in some weaknesses of the encryption algorithm. We show ::: three kinds of attacks in this paper, through which one can recover the plaintext from ::: a given ciphertext without the secret key. We also present an improvement on their ::: scheme, which prevents the three attacks mentioned above. Security of the enhanced ::: cipher is presented and analyzed, which shows that our improved scheme is secure under ::: the current attacks.
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paper_title: Some basic cryptographic requirements for chaos-based cryptosystems

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In recent years, a large amount of work on chaos-based cryptosystems have been published. However, many of the proposed schemes fail to explain or do not possess a number of features that are fundamentally important to all kind of cryptosystems. As a result, many proposed systems are difficult to implement in practice with a reasonable degree of security. Likewise, they are seldom accompanied by a thorough security analysis. Consequently, it is difficult for other researchers and end users to evaluate their security and performance. This work is intended to provide a common framework of basic guidelines that, if followed, could benefit every new cryptosystem. The suggested guidelines address three main issues: implementation, key management and security analysis, aiming at assisting designers of new cryptosystems to present their work in a more systematic and rigorous way to fulfill some basic cryptographic requirements. Meanwhile, several recommendations are made regarding some practical aspects of analog chaos-based secure communications, such as channel noise, limited bandwith and attenuation.
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paper_title: A new chaos-based fast image encryption algorithm

paper_content:

In recent years, various image encryption algorithms based on the permutation-diffusion architecture have been proposed where, however, permutation and diffusion are considered as two separate stages, both requiring image-scanning to obtain pixel values. If these two stages are combined, the duplicated scanning effort can be reduced and the encryption can be accelerated. In this paper, a fast image encryption algorithm with combined permutation and diffusion is proposed. First, the image is partitioned into blocks of pixels. Then, spatiotemporal chaos is employed to shuffle the blocks and, at the same time, to change the pixel values. Meanwhile, an efficient method for generating pseudorandom numbers from spatiotemporal chaos is suggested, which further increases the encryption speed. Theoretical analyses and computer simulations both confirm that the new algorithm has high security and is very fast for practical image encryption.
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paper_title: CRYPTANALYSIS OF OBSERVER BASED DISCRETE-TIME CHAOTIC ENCRYPTION SCHEMES

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This paper investigates the weaknesses of cryptosystems that use observer based synchronized chaotic systems. It is shown that known plaintext and chosen plaintext attacks can successfully be launched against such cryptosystems to recover the system parameters and subsequently eavesdrop on the message transmission. The methods employed rely only on the basic mathematical relations that exist between the output sequence and the message sequence of the transmitter system and require very less computations.
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paper_title: Introduction to Algorithms

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From the Publisher: ::: The updated new edition of the classic Introduction to Algorithms is intended primarily for use in undergraduate or graduate courses in algorithms or data structures. Like the first edition,this text can also be used for self-study by technical professionals since it discusses engineering issues in algorithm design as well as the mathematical aspects. ::: In its new edition,Introduction to Algorithms continues to provide a comprehensive introduction to the modern study of algorithms. The revision has been updated to reflect changes in the years since the book's original publication. New chapters on the role of algorithms in computing and on probabilistic analysis and randomized algorithms have been included. Sections throughout the book have been rewritten for increased clarity,and material has been added wherever a fuller explanation has seemed useful or new information warrants expanded coverage. ::: As in the classic first edition,this new edition of Introduction to Algorithms presents a rich variety of algorithms and covers them in considerable depth while making their design and analysis accessible to all levels of readers. Further,the algorithms are presented in pseudocode to make the book easily accessible to students from all programming language backgrounds. ::: Each chapter presents an algorithm,a design technique,an application area,or a related topic. The chapters are not dependent on one another,so the instructor can organize his or her use of the book in the way that best suits the course's needs. Additionally,the new edition offers a 25% increase over the first edition in the number of problems,giving the book 155 problems and over 900 exercises thatreinforcethe concepts the students are learning.
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paper_title: Breaking two secure communication systems based on chaotic masking

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This paper describes the security weakness of two generalized nonlinear state-space observers-based approaches for both chaos synchronization and secure communication, using chaotic masking and chaotic modulation of a Lorenz system. We show that the security is compromised without any knowledge of the chaotic system parameter values and even without knowing the transmitter structure.
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paper_title: Hierarchical Selective Encryption for G.729 Speech Based on Bit Sensitivity

paper_content:

Speech encryption is becoming increasingly important as the increasing relevance of multimedia applications such as video conference and news broadcasting. However, multimedia encryption and decryption are often computationally demanding and unpractical for power-constrained devices and narrow bandwidth environments. It is a challenge to obtain a good tradeoff between high security and low computational cost. To tackle this situation, a group of hierarchical selective encryption schemes are presented based on the computational complexity analysis of G.729 standard speech in this paper. In the proposed schemes, speech bit streams are partitioned into two parts according to the bit sensitivity, i.e., one is encrypted by a strong cipher and the other by a lightweight cipher. The contrast experiments are addressed in signal inspection and objective distortion measure. Additionally, we discuss the schemes' cryptanalysis is investigated. The results demonstrate the effectiveness of the hierarchical selective encryption schemes for power-constrained devices and narrow bandwidth environments.
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paper_title: Efficient video encryption scheme based on advanced video coding

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A video encryption scheme combining with advanced video coding (AVC) is presented and analyzed in this paper, which is different from the ones used in MPEG1/2 video encryption. In the proposed scheme, the intra-prediction mode and motion vector difference are encrypted with the length-kept encryption algorithm (LKE) in order to keep the format compliance, and the residue data of the macroblocks are encrypted with the residue data encryption algorithm (RDE) in order to keep low cost. Additionally, a key distribution scheme is proposed to keep the robustness to transmission errors, which assigns sub-keys to different frames or slices independently. The encryption scheme's security, time efficiency and error robustness are analyzed in detail. Experimental results show that the encryption scheme keeps file format unchanged, is secure against replacement attacks, is efficient in computing, and is robust to some transmission errors. These properties make it a suitable choice for real-time applications, such as secure IPTV, secure videoconference or mobile/wireless multimedia, etc.
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paper_title: Analysis and Design of Stream Ciphers

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1. Introduction.- 2. Stream Ciphers.- 2.1. Theoretical versus Practical Security.- 2.2. The Key Stream Generator.- 2.3. The Synchronization (Problem) of Stream Ciphers.- 3. Algebraic Tools.- 3.1. Finite Fields and Polynomials.- 3.2. Linear Feedback Shift Registers (LFSRs) and Sequences.- 3.3. Minimal Polynomial and Traces.- 4. Random Sequences and Linear Complexity.- 5. Nonlinear Theory of Periodic Sequences.- 5.1. Nonlinear Operations on Phases of a Sequence with Irreducible Minimal Polynomial.- 5.2. Nonlinear Operations on Sequences with Distinct Minimal Polynomials.- 5.3. Correlation-Immunity of Memoryless Combining Functions.- 5.4. Summary and Conclusions.- 6. Multiple Speed: An Additional Parameter in Secure Sequence Generation.- 6.1. The Simulated Linear Feedback Shift Register.- 6.2. A Random Number Generator Suggested by a Linear Cipher Problem.- 6.2.1. The Random Sequence Generator.- 6.2.2. Analysis of the Random Sequence Generator.- 6.2.3. Extensions and Comments.- 7. The Knapsack as a Nonlinear Function.- 7.1. The Significance of the Knapsack for Secrecy Systems.- 7.2. Addition is a Cryptographically Useful Function.- 7.3. The Knapsack in GF(2)-Arithmetic.- 8. The Hard Knapsack Stream Cipher.- 8.1. System Description.- 8.2. Analysis of the Knapsack Stream Cipher.- 8.3. Conclusions and Design Considerations.- 8.4. Simulation Results of Small Scale Knapsack Stream Ciphers.- 9. Nonlinear Combining Functions with Memory.- 9.1. Correlation Immunity.- 9.2. The Summation Principle.- 9.3. Summary and Conclusions.- Literature References.
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paper_title: Chaos-Based Video Encryption Algorithms

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In recent years, with the development of network technology and multimedia technology, multimedia data, especially video data, are used more and more widely in human society. Some multimedia data applied in entertainment, politics, economics, militaries, industries or education, etc., are necessary to be protected by providing confidentiality, integrity, and ownership or identity. To protect video contents, cryptology, which appears to be an effective way for information security, has been employed in many practical applications[1][2][3]. However, traditional ciphers like DES [4], IDEA [5], RSA[6] and AES[7], are often used for text or binary data, while not suitable for direct video encryption because of the following reasons.
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paper_title: Transmission Error and Compression Robustness of 2D Chaotic Map Image Encryption Schemes

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This paper analyzes the robustness properties of 2D chaotic map image encryption schemes. We investigate the behavior of such block ciphers under different channel error types and find the transmission error robustness to be highly dependent on on the type of error occurring and to be very different as compared to the effects when using traditional block ciphers like AES. Additionally, chaotic-mixing-based encryption schemes are shown to be robust to lossy compression as long as the security requirements are not too high. This property facilitates the application of these ciphers in scenarios where lossy compression is applied to encrypted material, which is impossible in case traditional ciphers should be employed. If high security is required chaotic mixing loses its robustness to transmission errors and compression, still the lower computational demand may be an argument in favor of chaotic mixing as compared to traditional ciphers when visual data is to be encrypted.
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paper_title: A chaos-based unequal encryption mechanism in wireless telemedicine with error decryption

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In this paper, we have developed a chaos-based unequal encryption mechanism which can be applied in the wireless telemedicine with error decryption. The main idea for using chaos sequence is to increase the unpredictability compared with other kinds of random sequences. An essential feature of this unequal encryption scheme is that a bit stream mapping of 1D chaotic scrambler and a permutation scheme are allocated to the medical information that requires higher level encryption. In addition, a bit stream mapping of 1D chaotic scrambler is provided to messages that can meet high speed encryption. Simulation results show when a correct deciphering parameter is put in, these signals will be completely recovered. As long as there is an input parameter error, for example, with 0.00000001% initial point error, these signals will not be recovered.
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paper_title: Chaos-based image encryption algorithm ✩

paper_content:

In this Letter, a new image encryption scheme is presented, in which shuffling the positions and changing the grey values of image pixels are combined to confuse the relationship between the cipher-image and the plain-image. Firstly, the Arnold cat map is used to shuffle the positions of the image pixels in the spatial-domain. Then the discrete output signal of the Chen's chaotic system is preprocessed to be suitable for the grayscale image encryption, and the shuffled image is encrypted by the preprocessed signal pixel by pixel. The experimental results demonstrate that the key space is large enough to resist the brute-force attack and the distribution of grey values of the encrypted image has a random-like behavior.
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paper_title: A new chaos-based fast image encryption algorithm

paper_content:

In recent years, various image encryption algorithms based on the permutation-diffusion architecture have been proposed where, however, permutation and diffusion are considered as two separate stages, both requiring image-scanning to obtain pixel values. If these two stages are combined, the duplicated scanning effort can be reduced and the encryption can be accelerated. In this paper, a fast image encryption algorithm with combined permutation and diffusion is proposed. First, the image is partitioned into blocks of pixels. Then, spatiotemporal chaos is employed to shuffle the blocks and, at the same time, to change the pixel values. Meanwhile, an efficient method for generating pseudorandom numbers from spatiotemporal chaos is suggested, which further increases the encryption speed. Theoretical analyses and computer simulations both confirm that the new algorithm has high security and is very fast for practical image encryption.
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paper_title: Distinguishing random and deterministic systems: Abridged version

paper_content:

Abstract This paper attempts to give a mathematically precise version of recent tests on an observed time series {at} for the presence of low dimensional deterministic chaos. Three practical tests for chaos are discussed: (a) the correlation dimension of {at} must be low, (b) the estimated largest Lyapunov exponent must be positive, (c) the residuals {at} of an estimated linear time (or nonlinear) series model (for a large class of such models) must have the same dimension and largest Lyapunov exponent as {at}. Based on (a)-(c) evidence for chaos in post war II, U.S. quarterly real GNP is weak.
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paper_title: Cryptanalysis of a chaos-based image encryption algorithm

paper_content:

A chaos-based image encryption algorithm was proposed in [Z.-H. Guan, F. Huang, W. Guan, Phys. Lett. A 346 (2005) 153]. In this Letter, we analyze the security weaknesses of the proposal. By applying chosen-plaintext and known-plaintext attacks, we show that all the secret parameters can be revealed.
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paper_title: Security Analysis of A Chaos-based Image Encryption Algorithm

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The security of Fridrich Image Encryption Algorithm against brute-force attack, statistical attack, known-plaintext attack and select-plaintext attack is analyzed by investigating the properties of the involved chaotic maps and diffusion functions. Based on the given analyses, some means are proposed to strengthen the overall performance of the focused cryptosystem.
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paper_title: Image encryption algorithm based on chaotic mapping

paper_content:

Image scrambling is one important method in image encryption field. By using some characteristics of chaos system, e.g. the sensitivity to initial conditions, the sensitivity to parameter and the pseudo-randomicity, this paper presents one image scrambling algorithm based on chaotic mapping. In order to achieve an effect of image scrambling, each pair of pixel points is exchanged for all the possible pair combinations. Compared to other image encryption algorithms which are based on chaotic mapping, this algorithm has some advantages, e.g. simplicity in design and high efficiency. In this paper, the methodology for evaluating image scrambling degree which is based on the position correlation is adopted to evaluate the encryption effect, which is consistent with the results of subjective evaluation.
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paper_title: Image encryption based on chaotic maps

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In this paper, it is shown how to adapt certain invertible chaotic 2D maps on a torus or on a square to create new symmetric block encryption schemes. The schemes are especially useful for encryption of large amounts of data, such as digital images or electronic databases. A chaotic map is first generalized by introducing parameters and then discretized to a finite square lattice of points which represent pixels or some other data items. Although the discretized map is a permutation and thus cannot be chaotic, it shares certain sensitivity and mixing properties with its continuous counterpart as long as the number of iterations remains small. It is shown that for the 2D baker map the permutations behave as typical random permutations. The discretized map is further extended to 3D and composed with a simple diffusion mechanism. As a result, a block product encryption scheme is obtained. To encrypt an N/spl times/N image, the ciphering map is iteratively applied to the image. This paper is an extension of the work of Pichler and Scharinger (1994, 1996) who first introduced encryption schemes based on 2D baker map.
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paper_title: Analysis and improvement of a chaos-based image encryption algorithm

paper_content:

Abstract The security of digital image attracts much attention recently. In Guan et al. [Guan Z, Huang F, Guan W. Chaos-based image encryption algorithm. Phys Lett A 2005; 346: 153–7.], a chaos-based image encryption algorithm has been proposed. In this paper, the cause of potential flaws in the original algorithm is analyzed in detail, and then the corresponding enhancement measures are proposed. Both theoretical analysis and computer simulation indicate that the improved algorithm can overcome these flaws and maintain all the merits of the original one.
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paper_title: Selective Encryption for G.729 Speech Using Chaotic Maps

paper_content:

Speech encryption is becoming increasingly important as the increasing relevance of multimedia applications such as video conference and news broadcasting. However, multimedia encryption and decryption are often computationally demanding and unpractical for power-constrained devices and narrow bandwidth environments. To tackle this situation, two novel selective encryption schemes are presented for G.729 speech in this paper. In the proposed schemes, speech bitstreams are partitioned into two parts based on bit sensitivity, i.e., one is encrypted by a high degree of encryption, and the other is encrypted by a lesser degree. To test the schemes, we introduce two chaotic maps, i.e., cat map and logistic map, and give contrast experiments addressed in signal inspection and objective distortion measure. Additionally, we discuss the two schemes' cryptanalysis and computational complexity. The results demonstrate the effectiveness of our selective encryption schemes for power-constrained devices and narrow bandwidth environments.
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paper_title: Pattern dynamics in spatiotemporal chaos: Pattern selection, diffusion of defect and pattern competition intermettency

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Abstract A class of coupled map lattices is investigated as a model for the spatiotemporal chaos. As the parameters are changed, phase transitions among the patterns are observed. Pattern selection through the chaotic motion of domain is observed. Chaos is suppressed by the selection. Selection of the zigzag pattern is studied, where localized defects which separate the two anti-phase domains are found. They change chaotically in time and move randomly in space. The diffusion of defect is related with its chaotic motion. Collapse of zigzag pattern and the defect turbulence are studied in connection with the crisis in high-dimensional dynamical systems. Pattern selection with longer wavelengths is found in the stronger coupling regime. Transition from pattern selection phase to fully developed turbulence occurs via the intermittency. Selective flicker-like noise and the Pareto distribution of lifetime of pattern are observed at the intermittency regime. For the quantitative characterization of each phase, pattern distributions, pattern transition matrix, static and dynamical entropies, lifetime distribution of pattern, spatiotemporal power spectra, and Lyapunov spectra are calculated. Phase transition from the pattern selection to fully developed turbulence is investigated with the use of these quantifiers, where some order parameters and critical indeces are introduced.
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paper_title: A block cipher based on a suitable use of the chaotic standard map

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Abstract Due to their features of ergodicity, sensitivity to initial conditions and sensitivity to control parameters, etc., chaotic maps have good potential for information encryption. In this paper, a block cipher based on the chaotic standard map is proposed, which is composed of three parts: a confusion process based on chaotic standard map, a diffusion function, and a key generator. The parameter sensitivity of the standard map is analyzed, and the confusion process based on it is proposed. A diffusion function with high diffusion speed is designed, and a key generator based on the chaotic skew tent map is derived. Some cryptanalysis on the security of the designed cipher is carried out, and its computational complexity is analyzed. Experimental results show that the new cipher has satisfactory security with a low cost, which makes it a potential candidate for encryption of multimedia data such as images, audios and even videos.
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paper_title: Construction and Analysis of One Class of Chaotic Running Key Generator

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This paper proposed a method of constructing one class of chaotic running key generator based on time varied parameter piecewise linear maps(PLM). No local linear structure exists in the phase portrait of the generated analogical chaotic series, and the key sequences generated by this generator have ideal cryptographic properties.
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paper_title: Yet another chaotic attractor

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This Letter reports the finding of a new chaotic at tractor in a simple three-dimensional autonomous system, which resembles some familiar features from both the Lorenz and Rossler at tractors.
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paper_title: A new image encryption algorithm based on hyper-chaos

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This Letter presents a new image encryption scheme, which employs an image total shuffling matrix to shuffle the positions of image pixels and then uses a hyper-chaotic system to confuse the relationship between the plain-image and the cipher-image. The experimental results demonstrate that the suggested encryption algorithm of image has the advantages of large key space and high security, and moreover, the distribution of grey values of the encrypted y image has a random-like behavior.
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paper_title: A fast image encryption system based on chaotic maps with finite precision representation

paper_content:

Abstract In this paper, a fast chaos-based image encryption system with stream cipher structure is proposed. In order to achieve a fast throughput and facilitate hardware realization, 32-bit precision representation with fixed point arithmetic is assumed. The major core of the encryption system is a pseudo-random keystream generator based on a cascade of chaotic maps, serving the purpose of sequence generation and random mixing. Unlike the other existing chaos-based pseudo-random number generators, the proposed keystream generator not only achieves a very fast throughput, but also passes the statistical tests of up-to-date test suite even under quantization. The overall design of the image encryption system is to be explained while detail cryptanalysis is given and compared with some existing schemes.
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paper_title: Image encryption with compound chaotic sequence cipher shifting dynamically

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We design a new two-dimensional chaotic function using two one-dimensional chaotic functions, and then prove the chaotic properties to a new function based on a strict Devaney definition. And we propose a new encrypting image scheme using the new compound chaotic function by choosing one of the two one-dimensional chaotic functions randomly. We give statistical analysis, sequence random analysis, and sensitivity analysis to plaintext and key on the proposed scheme. The experimental results show that the new scheme has a very fast encryption speed and the key space is expanded and it can resist all kinds of cryptanalytic, statistical and brute-force attacks, and especially, our new method can be also used to solve the problem that is easily exposed to chosen plaintext attack and low digitization of one-dimensional chaotic function.
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paper_title: Cryptanalysis of a new image encryption algorithm based on hyper-chaos

paper_content:

This Letter proposes two different attacks on a recently proposed image based on hyper-chaos. The cryptosystem under study proceed first by shuffling the image rows and columns to disturb the high correlation among pixels by iterating the logistic map. Second, a keystream is generated to mix it with the pixels of the shuffled image using hyper-chaos. These two processes in the encryption stage present weakness, and a chosen plaintext attack and a chosen ciphertext attack can be done to recover the ciphered-image without any knowledge of the key value. It just demands three couples of plaintext/ciphertext to break totally the cryptosystem.
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paper_title: An efficient diffusion approach for chaos-based image encryption

paper_content:

Abstract One of the existing chaos-based image cryptosystems is composed of alternative substitution and diffusion stages. A multi-dimensional chaotic map is usually employed in the substitution stage for image pixel permutation while a one-dimensional (1D) chaotic map is used for diffusion purpose. As the latter usually involves real number arithmetic operations, the overall encryption speed is limited by the diffusion stage. In this paper, we propose a more efficient diffusion mechanism using simple table lookup and swapping techniques as a light-weight replacement of the 1D chaotic map iteration. Simulation results show that at a similar security level, the proposed cryptosystem needs about one-third the encryption time of a similar cryptosystem. The effective acceleration of chaos-based image cryptosystems is thus achieved.
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paper_title: An image encryption approach based on chaotic maps

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Abstract It is well-known that images are different from texts in many aspects, such as highly redundancy and correlation, the local structure and the characteristics of amplitude–frequency. As a result, the methods of conventional encryption cannot be applicable to images. In this paper, we improve the properties of confusion and diffusion in terms of discrete exponential chaotic maps, and design a key scheme for the resistance to statistic attack, differential attack and grey code attack. Experimental and theoretical results also show that our scheme is efficient and very secure.
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paper_title: A Chaotic-Neural-Network-Based Encryption Algorithm for JPEG2000 Encoded Images

paper_content:

In this paper, a cipher based-on chaotic neural network is proposed, which is used to encrypt JPEG2000 encoded images. During the image encoding process, some sensitive bitstreams are selected from different subbands, bit-planes or encoding-passes, and then are completely encrypted. The algorithm has high security with low cost; it can keep the original file format and compression ratio unchanged, and can support direct operations such as image browsing and bit-rate control. These properties make the cipher very suitable for such real-time encryption applications as image transmission, web imaging, mobile and wireless multimedia communication.
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paper_title: Techniques For A Selective Encryption Of Uncompressed And Compressed images

paper_content:

This paper describes several techniques to encrypt uncompressed and compressed images. We first present the aims of image encryption. In the usual ways to encryption, all the information is encrypted. But this is not mandatory. In this paper we follow the principles of a technique initially proposed by MAPLES et al. [1] and encrypt only a part of the image content in order to be able to visualize the encrypted images, although not with full precision. This concept leads to techniques that can simultaneously provide security functions and an overall visual check which might be suitable in some applications like, for example, searching through a shared image database. The principle of selective encryption is first applied to uncompressed images. Then we propose a simple technique applicable to the particular case of JPEG images. This technique is proven not to interfere with the decoding process in the sense that it achieves a constant bit rate and that bitstreams remain compliant to the JPEG specifications. Then we develop a scheme called multiple selective encryption, discuss its properties and conclude.
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paper_title: Perception-based partial encryption of compressed speech

paper_content:

Mobile multimedia applications, the focus of many forthcoming wireless services, increasingly demand low-power techniques implementing content protection and customer privacy. In this paper low complexity perception-based partial encryption schemes for speech are presented. Speech compressed by a widely-used speech coding algorithm, the ITU-T G.729 standard at 8 kb/s, is partitioned in two classes, one, the most perceptually relevant, to be encrypted, the other, to be left unprotected. Two partial-encryption techniques are developed, a low-protection scheme, aimed at preventing most kinds of eavesdropping and a high-protection scheme, based on the encryption of a larger share of perceptually important bits and meant to perform as well as full encryption of the compressed bitstream. The high-protection scheme, based on the encryption of about 45% of the bitstream, achieves content protection comparable to that obtained by full encryption, as verified by both objective measures and formal listening tests. For the low-protection scheme, encryption of as little as 30% of the bitstream virtually eliminates intelligibility as well as most of the remaining perceptual information. Low-power, portable devices could therefore achieve very high levels of speech-content protection at only 30-45% of the computational load of current techniques, freeing resources for other tasks and enabling longer battery life.
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paper_title: Chaotic secure image coding based on SPIHT

paper_content:

From the viewpoint of Shannon?s information theory, image coding and image encryption both aim at reducing the correlations of pixels. However, current image encoding methods did not take the confidentiality into account. In this paper, a novel chaotic image encryption scheme integrated with the SPIHT wavelet image coding is proposed. Comparing with the existing image encryption schemes, the new method has three prominent advantages: first, only sensitive bits in the coding stream are encrypted, which introduces small overheads to the image codec; second, by introducing a cipher-text feedback mechanism, the scheme can effectively resist the known-plain-text attack; third, by using chaotic pseudo-random bits to mask the SPIHT encoded bitstream, the scheme can truncate the output stream at any position while keeping the image recoverable with different visual qualities. Cryptanalysis and various experiments have been carried out and the results were reported in this paper, which demonstrate the feasibility and flexibility of the proposed scheme.
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paper_title: Partial Encryption of Compressed Images and Videos

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The increased popularity of multimedia applications places a great demand on efficient data storage and transmission techniques. Network communication, especially over a wireless network, can easily be intercepted and must be protected from eavesdroppers. Unfortunately, encryption and decryption are slow, and it is often difficult, if not impossible, to carry out real-time secure image and video communication and processing. Methods have been proposed to combine compression and encryption together to reduce the overall processing time, but they are either insecure or too computationally intensive. We propose a novel solution called partial encryption, in which a secure encryption algorithm is used to encrypt only part of the compressed data. Partial encryption is applied to several image and video compression algorithms in this paper. Only 13-27% of the output from quadtree compression algorithms is encrypted for typical images, and less than 2% is encrypted for 512/spl times/512 images compressed by the set partitioning in hierarchical trees (SPIHT) algorithm. The results are similar for video compression, resulting in a significant reduction in encryption and decryption time. The proposed partial encryption schemes are fast, secure, and do not reduce the compression performance of the underlying compression algorithm.
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paper_title: Selective encryption of wavelet-packet encoded image data: efficiency and security

paper_content:

Selective encryption provides the ability to strike a balance between security and processing demands, e.g., in mobile clients. Image encoding using wavelets, and especially wavelet packets, can be used for efficient selective encryption. We will show how two such methods work and discuss their advantages and disadvantages in terms of security and speed.
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paper_title: Selective image encryption using a spatiotemporal chaotic system

paper_content:

A universal selective image encryption algorithm, in which the spatiotemporal chaotic system is utilized, is proposed to encrypt gray-level images. In order to resolve the tradeoff between security and performance, the effectiveness of selective encryption is discussed based on simulation results. The scheme is then extended to encrypt RGB color images. Security analyses for both scenarios show that the proposed schemes achieve high security and efficiency.
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paper_title: Frequency-selective partial encryption of compressed audio

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The widespread adoption of compressed digital audio increasingly demands effective ways to conjugate ease of distribution with content protection. In this paper a low-complexity partial-encryption scheme for MPEG audio is presented. The aim is to provide listeners with sample-quality audio material that can be upgraded to full-quality by simply acquiring a key and decrypting a few selected bits (1-10% of the total bitstream) of the already available data. Sample-quality is obtained by limiting the frequency content of the signal, and it is achieved without altering the compatibility of the compressed audio bitstream. Audio material partially encrypted with the proposed scheme can thus be freely distributed for evaluation and then easily unlocked to achieve full quality without any further transmission of audio data.
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paper_title: Fast encryption methods for audiovisual data confidentiality

paper_content:

Two methodologies for efficient audiovisual data encryption are studied in this research, i.e. selective encryption and MHT (multiple-Huffman-table). We first discuss benefits and limitations of selective encryption, and propose a selective encryption scheme for ITU G.723.1 speech coding. A review of all cryptanalysis work of selective encryption algorithms in the literature is given, our cryptanalysis for the JPEG/MPEG sign-bit encryption scheme is presented, and two rules to determine whether selective encryption for a compression system is suitable are concluded. Then, we investigate another encryption methodology via the manipulation of Huffman coding tables of multimedia coding systems. The MHT scheme chooses several different Huffman tables from a vast number of possible candidates, and uses them alternatively to encode multimedia data. The choice of Huffman tables and the order that they are used are kept secret as the key. This method requires very little computational overhead, and can be applied to the encryption of MPEG audio, MPEG video and JPEG/JPEG2000 images.
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paper_title: Hierarchical Selective Encryption for G.729 Speech Based on Bit Sensitivity

paper_content:

Speech encryption is becoming increasingly important as the increasing relevance of multimedia applications such as video conference and news broadcasting. However, multimedia encryption and decryption are often computationally demanding and unpractical for power-constrained devices and narrow bandwidth environments. It is a challenge to obtain a good tradeoff between high security and low computational cost. To tackle this situation, a group of hierarchical selective encryption schemes are presented based on the computational complexity analysis of G.729 standard speech in this paper. In the proposed schemes, speech bit streams are partitioned into two parts according to the bit sensitivity, i.e., one is encrypted by a strong cipher and the other by a lightweight cipher. The contrast experiments are addressed in signal inspection and objective distortion measure. Additionally, we discuss the schemes' cryptanalysis is investigated. The results demonstrate the effectiveness of the hierarchical selective encryption schemes for power-constrained devices and narrow bandwidth environments.
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paper_title: Efficient image or video encryption based on spatiotemporal chaos system

paper_content:

Abstract In this paper, an efficient image/video encryption scheme is constructed based on spatiotemporal chaos system. The chaotic lattices are used to generate pseudorandom sequences and then encrypt image blocks one by one. By iterating chaotic maps for certain times, the generated pseudorandom sequences obtain high initial-value sensitivity and good randomness. The pseudorandom-bits in each lattice are used to encrypt the Direct Current coefficient (DC) and the signs of the Alternating Current coefficients (ACs). Theoretical analysis and experimental results show that the scheme has good cryptographic security and perceptual security, and it does not affect the compression efficiency apparently. These properties make the scheme a suitable choice for practical applications.
---
paper_title: Encryption of Digital Video Based on Lorenz Chaotic System

paper_content:

A novel video encryption scheme based on chaotic maps is performed. First the video sequence to be encrypted is taken. Then it is split up into frames. If the frames are larger in size, then it is broken into macro-blocks for the operation. The high dimensional Lorenz chaotic system is employed to confuse the position of the pixels. Multi-key concept is used to improve the security of the cryptosystem against attacks. Security analysis is performed to test the proposed cryptosystem and the system is proved to be robust against various attacks.
---
paper_title: A chaotic stream cipher and the usage in video protection

paper_content:

Abstract In this paper, a chaotic stream cipher is constructed and used to encrypt video data selectively. The stream cipher based on a discrete piecewise linear chaotic map satisfies the security requirement of cipher design. The video encryption scheme based on the stream cipher is secure in perception, efficient and format compliant, which is suitable for practical video protection. The video encryption scheme’s performances prove the stream cipher’s practicability.
---
paper_title: A video encryption method based on chaotic maps in DCT domain

paper_content:

Abstract This paper proposes a new and secure video encryption method based on chaotic maps in DCT domain, which is quite in keeping with the common ideas and the frequent practices of video encryption. We select the I-frames of the video sequence as encryption objects. First, we introduce two coupling chaotic maps to scramble the DCT coefficients of every original I-frame, and receive the scrambled I-frame. Second, we encrypt the DCT coefficients of the scrambled I-frame using another chaotic map. In the whole process, we use three chaotic maps and five keys; the I-frame is encrypted twice. Finally, we performed several tests and the experimental results have proved our method to be secure and efficient.
---
paper_title: Chaotic video objects encryption based on mixed feedback, multiresolution decomposition and time-variant S-boxes

paper_content:

The increasing popularity of multimedia applications creates an increasing need for secure storage and transmission techniques. Especially wireless communications, which can be easily intercepted, should be protected by eavesdroppers. Towards this direction, several encryption schemes have been proposed in literature, however most of them do not consider regions of interest (video objects). These regions may need better protection, may be the only regions that need protection, or should be accessed separately according to different privileges. For these reasons in this paper a video objects chaotic encryption system is proposed. Initially stereoscopic pairs are analyzed and video objects are automatically extracted using a color segments fusion approach. Next for each video object multiresolution decomposition is performed and the pixels of the lowest resolution level are encrypted using a chaotic cipher module. Finally the encrypted regions are propagated to the higher resolution levels and the encryption process is repeated until the highest level is reached. The system presents robustness against known cryptanalytic attacks, enables layered access of multimedia content and the overall security can be enhanced due to region topology.
---
paper_title: Chaotic encryption of speech signals in transform domains

paper_content:

A speech encryption system based on substitution and permutation is described. The stream of speech segments is divided and reshaped into two fixed size blocks and the elements are permutated by chaotic map technique, then substituted to different values by discrete cosine transform (DCT) and then permutated another time to eliminate attacks with known plaintext attack. Finally, chaotic speech signals that completely different from original signal is generated. The proposed low complexity system will avoid the delay resulting from the use of simple substitution and fast permutation process. the target of the proposed system is to change the characteristics of speech signal and eliminate the intelligibility of the encrypted signal‥ The security aspects of the proposed system will depend on different parameters including secret blocks size, permutation process and variable number of rounds.
---
paper_title: Video Compression and Encryption Based-On Multiple Chaotic System

paper_content:

Different from most of recent studies or research on encryption algorithms based on chaotic system, the paper schemes out multiple chaotic system as an encryption approach not only after compressing video streams but also during the processing of compression frame by frame. The so-called multiple chaotic system actually consists of three chaotic or hyperchaotic maps, namely logistics map[l], 2-D Baker Map and a 4-D hyperchaotic Map[2].The three secret key encryptions are carried out as partial encryption when compressing the video data, and as block permutation and confusion after the video compression respectively. The implemented application fully substantiates the favorable efficiency of the proposed scheme such as speedy compression and encryption, overall high security and small size preservation.
---
paper_title: Security of human video objects by incorporating a chaos-based feedback cryptographic scheme

paper_content:

Security of multimedia files attracts more and more attention and many encryption methods have been proposed in literature. However most cryptographic systems deal with multimedia files as binary large objects, without taking into consideration regions of semantic information. These regions may need better protection or can be the only regions that need protection, depending on the specific application. Towards this direction, in this paper we propose a human video object encryption system based on the chaotic logistic map. Initially face regions are efficiently detected and afterwards body regions are extracted, using geometric information of the location of face regions. Next the pixels of extracted human video objects are encrypted using an iterative cipher module, which is based on a feedback mechanism responsible for mixing the current encryption parameters with encrypted information of the previous step. The system presents robustness against known cryptanalytic attacks, and can save us a great amount of computational resources and time devoted for encrypting the whole contents of a multimedia file.
---
paper_title: Public Key Encryption of Images and Videos in Real Time Using Chebyshev Maps

paper_content:

Due to rapid developments in limits and possibilities of communications and information transmissions, there is a growing demand of cryptographic techniques, which has spurred a great deal of intensive research activities in the study of cryptography. This paper describes a public key encryption based on chebyshev polynomials. We discuss the algorithm for textual data and present the cryptanalysis which can be performed on this algorithm for the recovery of encrypted data. We also describe a simple hashing algorithm for making this algorithm more secure, and which can also be used for digital signature. The main scope of this paper is to propose an extension of this algorithm to images and videos and making it secure using multilevel scrambling and hash. Software implementations and experimental results are also discussed in detail.
---
paper_title: Security of public-key cryptosystems based on Chebyshev polynomials

paper_content:

Chebyshev polynomials have been recently proposed for designing public-key systems. Indeed, they enjoy some nice chaotic properties, which seem to be suitable for use in Cryptography. Moreover, they satisfy a semi-group property, which makes possible implementing a trapdoor mechanism. In this paper, we study a public-key cryptosystem based on such polynomials, which provides both encryption and digital signature. The cryptosystem works on real numbers and is quite efficient. Unfortunately, from our analysis, it comes up that it is not secure. We describe an attack which permits to recover the corresponding plaintext from a given ciphertext. The same attack can be applied to produce forgeries if the cryptosystem is used for signing messages. Then, we point out that also other primitives, a Diffie-Hellman like key agreement scheme and an authentication scheme, designed along the same lines of the cryptosystem, are not secure due to the aforementioned attack. We close the paper by discussing the issues and the possibilities of constructing public-key cryptosystems on real numbers.
---
paper_title: Encryption of Digital Video Based on Lorenz Chaotic System

paper_content:

A novel video encryption scheme based on chaotic maps is performed. First the video sequence to be encrypted is taken. Then it is split up into frames. If the frames are larger in size, then it is broken into macro-blocks for the operation. The high dimensional Lorenz chaotic system is employed to confuse the position of the pixels. Multi-key concept is used to improve the security of the cryptosystem against attacks. Security analysis is performed to test the proposed cryptosystem and the system is proved to be robust against various attacks.
---
paper_title: Public Key Encryption of Images and Videos in Real Time Using Chebyshev Maps

paper_content:

Due to rapid developments in limits and possibilities of communications and information transmissions, there is a growing demand of cryptographic techniques, which has spurred a great deal of intensive research activities in the study of cryptography. This paper describes a public key encryption based on chebyshev polynomials. We discuss the algorithm for textual data and present the cryptanalysis which can be performed on this algorithm for the recovery of encrypted data. We also describe a simple hashing algorithm for making this algorithm more secure, and which can also be used for digital signature. The main scope of this paper is to propose an extension of this algorithm to images and videos and making it secure using multilevel scrambling and hash. Software implementations and experimental results are also discussed in detail.
---
paper_title: Chaotic video objects encryption based on mixed feedback, multiresolution decomposition and time-variant S-boxes

paper_content:

The increasing popularity of multimedia applications creates an increasing need for secure storage and transmission techniques. Especially wireless communications, which can be easily intercepted, should be protected by eavesdroppers. Towards this direction, several encryption schemes have been proposed in literature, however most of them do not consider regions of interest (video objects). These regions may need better protection, may be the only regions that need protection, or should be accessed separately according to different privileges. For these reasons in this paper a video objects chaotic encryption system is proposed. Initially stereoscopic pairs are analyzed and video objects are automatically extracted using a color segments fusion approach. Next for each video object multiresolution decomposition is performed and the pixels of the lowest resolution level are encrypted using a chaotic cipher module. Finally the encrypted regions are propagated to the higher resolution levels and the encryption process is repeated until the highest level is reached. The system presents robustness against known cryptanalytic attacks, enables layered access of multimedia content and the overall security can be enhanced due to region topology.
---
paper_title: Security of human video objects by incorporating a chaos-based feedback cryptographic scheme

paper_content:

Security of multimedia files attracts more and more attention and many encryption methods have been proposed in literature. However most cryptographic systems deal with multimedia files as binary large objects, without taking into consideration regions of semantic information. These regions may need better protection or can be the only regions that need protection, depending on the specific application. Towards this direction, in this paper we propose a human video object encryption system based on the chaotic logistic map. Initially face regions are efficiently detected and afterwards body regions are extracted, using geometric information of the location of face regions. Next the pixels of extracted human video objects are encrypted using an iterative cipher module, which is based on a feedback mechanism responsible for mixing the current encryption parameters with encrypted information of the previous step. The system presents robustness against known cryptanalytic attacks, and can save us a great amount of computational resources and time devoted for encrypting the whole contents of a multimedia file.
---
paper_title: Efficient image or video encryption based on spatiotemporal chaos system

paper_content:

Abstract In this paper, an efficient image/video encryption scheme is constructed based on spatiotemporal chaos system. The chaotic lattices are used to generate pseudorandom sequences and then encrypt image blocks one by one. By iterating chaotic maps for certain times, the generated pseudorandom sequences obtain high initial-value sensitivity and good randomness. The pseudorandom-bits in each lattice are used to encrypt the Direct Current coefficient (DC) and the signs of the Alternating Current coefficients (ACs). Theoretical analysis and experimental results show that the scheme has good cryptographic security and perceptual security, and it does not affect the compression efficiency apparently. These properties make the scheme a suitable choice for practical applications.
---
paper_title: A video encryption method based on chaotic maps in DCT domain

paper_content:

Abstract This paper proposes a new and secure video encryption method based on chaotic maps in DCT domain, which is quite in keeping with the common ideas and the frequent practices of video encryption. We select the I-frames of the video sequence as encryption objects. First, we introduce two coupling chaotic maps to scramble the DCT coefficients of every original I-frame, and receive the scrambled I-frame. Second, we encrypt the DCT coefficients of the scrambled I-frame using another chaotic map. In the whole process, we use three chaotic maps and five keys; the I-frame is encrypted twice. Finally, we performed several tests and the experimental results have proved our method to be secure and efficient.
---
paper_title: A new chaotic algorithm for video encryption

paper_content:

We present a new encryption algorithm for the video signal that, employing suitably arranged chaotic functions, allows to increase the security level while maintaining acceptable processing times. We analyze the performance of the new scheme either though simulation or via practical implementation, thus demonstrating its efficiency, also in comparison with previous proposals.
---
paper_title: A chaotic stream cipher and the usage in video protection

paper_content:

Abstract In this paper, a chaotic stream cipher is constructed and used to encrypt video data selectively. The stream cipher based on a discrete piecewise linear chaotic map satisfies the security requirement of cipher design. The video encryption scheme based on the stream cipher is secure in perception, efficient and format compliant, which is suitable for practical video protection. The video encryption scheme’s performances prove the stream cipher’s practicability.
---
paper_title: Video Compression and Encryption Based-On Multiple Chaotic System

paper_content:

Different from most of recent studies or research on encryption algorithms based on chaotic system, the paper schemes out multiple chaotic system as an encryption approach not only after compressing video streams but also during the processing of compression frame by frame. The so-called multiple chaotic system actually consists of three chaotic or hyperchaotic maps, namely logistics map[l], 2-D Baker Map and a 4-D hyperchaotic Map[2].The three secret key encryptions are carried out as partial encryption when compressing the video data, and as block permutation and confusion after the video compression respectively. The implemented application fully substantiates the favorable efficiency of the proposed scheme such as speedy compression and encryption, overall high security and small size preservation.
---
paper_title: Speech encryption in the transform domain

paper_content:

A comparison has been made of the use of five discrete orthogonal transforms in speech encryption systems. Four objective measures were used to grade the encryption systems with respect to residual intelligibility and recovered voice quality. A figure of merit based on all the objective measures was formed which gave good correlation to the subjective results of residual intelligibility and recovered speech quality.
---
paper_title: Blind source separation-based encryption of images and speeches

paper_content:

Blind source separation (BSS) has been successfully applied in many fields such as communications and biomedical engineering. Its application for image and speech encryption, however, has been scarce. Motivated by the fact that the security of many public-key cryptosystems relies on the apparent intractability of the computational problems such as the integer factorization problem, we present a BSS-based method for encrypting images and speeches by utilizing the BSS underdetermined problem. We discuss how to construct the mixing matrix for encryption and how to generate the key signals. Computer simulation results show that the BSS-based method has high level of security.
---
paper_title: Speech encryption based on fast Fourier transform permutation

paper_content:

This paper deals with the permutation of FFT (Fast Fourier Transform) coefficients in a speech encryption system. The scrambling algorithm is based on the permutation of the FFT coefficients and provides a highly secured scrambled signal by permuting a large number of those coefficients. The algorithm for the generation the permutation matrices is explained. This system is useful for a band limited telephone channel and mobile communication. Choice and construction of permutation matrices in the scrambling system are considered. Simulation has been carried out by using the C programming language. The results of simulation and tests show that the proposed scrambling achieves extremely high-level security as well as high speech quality.
---
paper_title: Chaotic encryption of speech signals in transform domains

paper_content:

A speech encryption system based on substitution and permutation is described. The stream of speech segments is divided and reshaped into two fixed size blocks and the elements are permutated by chaotic map technique, then substituted to different values by discrete cosine transform (DCT) and then permutated another time to eliminate attacks with known plaintext attack. Finally, chaotic speech signals that completely different from original signal is generated. The proposed low complexity system will avoid the delay resulting from the use of simple substitution and fast permutation process. the target of the proposed system is to change the characteristics of speech signal and eliminate the intelligibility of the encrypted signal‥ The security aspects of the proposed system will depend on different parameters including secret blocks size, permutation process and variable number of rounds.
---
paper_title: Speech privacy for modern mobile communication systems

paper_content:

Speech privacy techniques are used to scramble clear speech into an unintelligible signal in order to avoid eavesdropping. Some analog speech-privacy equipments (scramblers) have been replaced by digital encryption devices (comsec), which have higher degree of security but require complex implementations and large bandwidth for transmission. However, if speech privacy is wanted in a mobile phone using a modern commercial codec, such as the AMR (adaptive multirate) codec, digital encryption may not be an option due to the fact that it requires internal hardware and software modifications. If encryption is applied before the codec, poor voice quality may result, for the vocoder would handle digitally encrypted signal resembling noise. On the other hand, analog scramblers may be placed before the voice encoder without causing much penalty to its performance. Analog scramblers are intended in applications where the degree of security is not too critical and hardware modifications are prohibitive due to its high cost. In this article we investigate the use of different techniques of voice scramblers applied to mobile communications vocoders. We present our results in terms of LPC and cepstral distances, and PESQ values.
---
paper_title: Fast Fourier transform based speech encryption system

paper_content:

A speech encryption system based on permutation of DFT coefficients is described. This system was designed for use on a band limited telephone channel. The choice of permutation matrices and methods of synchronisation are discussed. Results of subjective and objective tests performed on the system are given which indicate low residual intelligibility and good recovered voice quality. The cryptanalytic strength of the system is also considered.
---
paper_title: Audio encryption using higher dimensional chaotic map

paper_content:

In Chaotic the properties of sensitivity to initial conditions, control parameters and pseudo- randomness chaotic maps have been widely used in data encryption recently. The chaotic based cryptosystems are suitable for large-scale data encryption such as images, videos or audio data. This paper propose a novel higher dimensional chaotic system for audio encryption, in which variables are treated as encryption keys in order to achieve secure transmission of audio signals. Since the highly sensitive to the initial condition of a system and to the variation of a parameter, and chaotic trajectory is so unpredictable. As a result we obtain much higher security. The higher dimensional of the algorithm is used to enhance the key space and security of the algorithm. The security analysis of the algorithm is given. The experiments show that the algorithm has the characteristic of sensitive to initial condition, high key space; digital audio signal distribution uniformity and the algorithm will not break in chosen/known-plaintext attacks.
---
paper_title: Audio encryption using higher dimensional chaotic map

paper_content:

In Chaotic the properties of sensitivity to initial conditions, control parameters and pseudo- randomness chaotic maps have been widely used in data encryption recently. The chaotic based cryptosystems are suitable for large-scale data encryption such as images, videos or audio data. This paper propose a novel higher dimensional chaotic system for audio encryption, in which variables are treated as encryption keys in order to achieve secure transmission of audio signals. Since the highly sensitive to the initial condition of a system and to the variation of a parameter, and chaotic trajectory is so unpredictable. As a result we obtain much higher security. The higher dimensional of the algorithm is used to enhance the key space and security of the algorithm. The security analysis of the algorithm is given. The experiments show that the algorithm has the characteristic of sensitive to initial condition, high key space; digital audio signal distribution uniformity and the algorithm will not break in chosen/known-plaintext attacks.
---
paper_title: A speech encryption using fractional chaotic systems

paper_content:

In this paper, a new speech encryption using fractional chaotic systems is presented. A two-channel transmission method is used where the original speech is encoded using a nonlinear function of the chaotic states. Conditions for synchronization between fractional chaotic systems through one variable have been investigated theoretically by using the Laplace transform. The keys, key space, key selection rules, and sensitivity to keys are discussed in detail. Results show that the original speech is well masked in the ciphertexts yet recovered faithfully and efficiently by the present schemes.
---

Title: Multimedia Security: A Survey of Chaos-Based Encryption Technology

Section 1: Introduction
Description 1: Introduces the significance of multimedia security in today's world and discusses the limitations of traditional ciphers in multimedia applications. Provides an overview of chaos-based encryption as a potential solution.

Section 2: Requirements of multimedia encryption
Description 2: Summarizes the special requirements of multimedia encryption due to unique characteristics like large data volumes, high redundancy, and the need for real-time responses.

Section 3: Security
Description 3: Elaborates on security as the primary requirement of multimedia encryption, detailing key aspects like perceptual security, key space, key sensitivity, and resistance to potential attacks.

Section 4: Other requirements
Description 4: Discusses additional requirements for multimedia encryption, such as computational complexity, invariance of compression ratio, format compliance, demand for real-time performance, multiple levels of security, and transmission error tolerance.

Section 5: Time analysis
Description 5: Describes the methods for analyzing encryption time, including absolute encryption time, relative encryption time ratio, and computational complexity.

Section 6: Compression ratio test
Description 6: Explains the methods for testing the compression ratio by comparing original compressed data volumes with encrypted and compressed data volumes.

Section 7: Error-robustness test
Description 7: Details the process of testing encryption schemes for robustness against transmission errors.

Section 8: Chaos-based image encryption algorithms
Description 8: Covers various existing chaos-based image encryption algorithms, including those based on chaotic block ciphers and chaotic stream ciphers, as well as full and partial encryption techniques.

Section 9: Performance comparison
Description 9: Compares the performance of different image encryption algorithms based on various aspects like key space, key sensitivity, computational complexity, and format compliance.

Section 10: Chaos-based video encryption algorithms
Description 10: Discusses chaos-based video encryption algorithms categorized by their relation to compression processes: encrypting raw video data, encrypting video data during compression, and encrypting compressed video data.

Section 11: Chaos-based audio encryption algorithms
Description 11: Details chaos-based and other audio encryption algorithms, distinguishing between analogue and digital approaches and outlining several specific methods.

Section 12: Conclusions
Description 12: Summarizes the importance of multimedia encryption and the potential of chaos-based multimedia encryptions, while acknowledging the need for further development to meet practical application requirements.