RAIRO-Theor. Inf. Appl.
Volume 47, Number 2, April-June 2013
|Page(s)||171 - 180|
|Published online||06 November 2012|
A tight bound for exhaustive key search attacks against Message Authentication Codes
Depto. de Ciência da Computação, Univ. Federal do Rio de
2 Inmetro, National Institute of Metrology, Quality and Technology, Brazil
email@example.com; firstname.lastname@example.org; email@example.com
Accepted: 3 September 2012
A Message Authentication Code (MAC) is a function that takes a message and a key as parameters and outputs an authentication of the message. MAC are used to guarantee the legitimacy of messages exchanged through a network, since generating a correct authentication requires the knowledge of the key defined secretly by trusted parties. However, an attacker with access to a sufficiently large number of message/authentication pairs may use a brute force algorithm to infer the secret key: from a set containing initially all possible key candidates, subsequently remove those that yield an incorrect authentication, proceeding this way for each intercepted message/authentication pair until a single key remains. In this paper, we determine an exact formula for the expected number of message/authentication pairs that must be used before such form of attack is successful, along with an asymptotical bound that is both simple and tight. We conclude by illustrating a modern application where this bound comes in handy, namely the estimation of security levels in reflection-based verification of software integrity.
Mathematics Subject Classification: 94A60
Key words: Cryptography / Message Authentication Code / asymptotic analysis
© EDP Sciences 2012
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