Differential Analysis Using Phase-Substitution

Among several countermeasures suggested for thwarting differential analysis are the random ordering of operations, insertion of random operations, and random insertion of operations. This paper presents a phase-substitution technique which in combination with subsequent time-domain differential analysis is shown to be able to thwart these three countermeasures in several experiments. Unlike previous techniques for aligning traces, this approach makes use of the phase information. The proposed technique involves: fast fourier transform, phase-substitution, inverse fast fourier transform and time-based differential analysis. Results are demonstrated using electromagnetic traces acquired from a PDA device (representing a complex embedded system including cache misses, operating system events, etc). This research is important for future wireless embedded systems which will increasingly demand higher levels of security.