Cryptology ePrint Archive: Report 2009/089

A Provably Secure And Efficient Countermeasure Against Timing Attacks

Boris Köpf and Markus Dürmuth

Abstract: We show that the amount of information about the key that an unknown-message attacker can extract from a deterministic side-channel is bounded from above by |O| \log_2 (n+1) bits, where n is the number of side-channel measurements and O is the set of possible observations. We use this bound to derive a novel countermeasure against timing attacks, where the strength of the security guarantee can be freely traded for the resulting performance penalty. We give algorithms that efficiently and optimally adjust this trade-off for given constraints on the side-channel leakage or on the efficiency of the cryptosystem. Finally, we perform a case-study that shows that applying our countermeasure leads to implementations with minor performance overhead and formal security guarantees.

Category / Keywords: applications / Side-Channel Attacks, Implementation, Information theory

Date: received 20 Feb 2009, last revised 7 May 2009

Contact author: bkoepf at mpi-sws mpg de

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Version: 20090507:113029 (All versions of this report)

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