Improving Efficiency of Key Enumeration Based on Side-Channel Analysis

Side-channel analysis (SCA) is usually used for analyzing the side-channel resistance of a crypto device. However, it does not mean "practical secure" when a SCA attack fails since SCA only provides a success or failure conclusion. On the basis of the SCA data about scores and ranks of all candidates for each subkey, it is still possible to apply key enumeration (KE) algorithms to search the correct master key at an affordable overhead. Nevertheless, the efficiency of KE is limited by the SCA data in essence. To address the issue, we proposed two methods to exploit the SCA data and Riemann integral of the rank curves of all subkey candidates to update each correct subkey rank before carrying out KE. We applied the proposed methods for different crypto implementations running on different devices to verify their performance. Experimental studies for both mono-channel and multi-channel leakages verified that the proposed methods were effective in improving the efficiency of KE to recover the correct key. The proposed methods are designed for processing the SCA data and can be deemed as a preliminary before executing KE. The work of this paper bridges the gap between SCA and KE.