Defensive Leakage Camouflage

This paper considers the transfer of digital data over leaky and noisy communication channels. We develop defensive strategies exploiting the fact that noise prevents the attacker from accurately measuring leakage. The defense strategy described in this paper pairs each useful data element k with a camouflage value v and simultaneously transmits both k and v over the channel. This releases an emission e(k, v). We wish to select the camouflage values v(k) as a function of k in a way that makes the quantities e(k, v(k)) as indistinguishable as possible from each other. We model the problem and show that optimal camouflage values can be computed from sidechannels under very weak physical assumptions. The proposed technique is hence applicable to a wide range of readily available technologies. We propose algorithms for computing optimal camouflage values when the number of samples per trace is moderate (typically ≤ 6) and justify our models by a statistical analysis. We also provide experimental results obtained using FPGAs.