Security by obscurity not so bad after all, argues prof

Game theory suggests secrecy has some uses

Security by obscurity may not be so bad after all, according to a provocative new research paper that questions long-held security maxims.

The Kerckhoffs' Principle holds that withholding information on how a system works is no security defence. A second accepted principle is that a defender has to defend against all possible attack vectors, whereas the attacker only needs to find one overlooked flaw to be successful, the so-called fortification principle.

However a new research paper from Prof Dusko Pavlovic of Royal Holloway, University of London, applies game theory to the conflict between hackers and security defenders in suggesting system security can be improved by making it difficult for attackers to figure out how their mark works. For example, adding a layer of obfuscation to a software application can make it harder to reverse engineer.

Pavlovic compares security to a game in which each side has incomplete information. Far from being powerless against attacks, a defender ought to be able to gain an advantage (or at least level the playing field) by examining an attacker's behaviour and algorithms while disguising defensive moves. At the same time defenders can benefit by giving away as few clues about their defensive posture as possible, an approach that the security by obscurity principle might suggest is futile.

Public key encryption works on the basis that making the algorithm used to derive a code secret is useless and codes, to be secure, need to be complex enough so that they can't be unpicked using a brute force attack. As computer power increases we therefore need to increase the length of an encryption key in order outstrip the computational power an attacker might have at his disposal. This still hold true for cryptography, as Pavlovic acknowledges, but may not be case in other scenarios.

Pavlovic argues that an attacker's logic or programming capabilities, as well as the computing resources at their disposal, might also be limited, suggesting that potential shortcomings in this area can be turned to the advantage of system defenders.

The paper, which is likely to spawn a lively debate, Gaming security by obscurity, can be found here. ®

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