## Cryptology ePrint Archive: Report 2010/391

Exponential Bounds for Information Leakage in Unknown-Message Side-Channel Attacks

Daniel Z. Zanger

Abstract: In Backes&Kopf(2008), the authors introduced an important new information theoretic numerical measure for assessing a system's resistance to unknown-message side-channel attacks and computed a formula for the limit of the numerical values defined by this measure as the number of side-channel observations tends to infinity. Here, we present corresponding quantitative (exponential) bounds that yield an actual rate-of-convergence for this limit, something not given in Backes&Kopf(2008). Such rate-of-convergence results can potentially be used to significantly strengthen the utility of the limit formula of Backes&Kopf(2008) as a tool to reduce computational complexity difficulties associated with calculating the side-channel attack resistance measure presented there. In addition, our arguments here show how the arguments used in Backes&Kopf(2008) to prove the limit formula can be substantially simplified.

Category / Keywords: Side Channel Attacks, Information Theory