Filtering-based CPA: a successful side-channel attack against desynchronization countermeasures

Secure implementations against side channel attacks usually combine hiding and masking protections in software implementations. In this work, we focus on desynchronization protection which is considered as a hiding countermeasure. The idea of desynchronization is to obtain a non-predictable offset of the attacking point in terms of time dimension. For this purpose, we present exploiting pattern-recognition methods to filter interesting points for obtaining a successful side channel attack. Using this tool as a case study, we completely cancel the desynchronization effect of the CHES 2009/2010 countermeasure [2, 3]. Moreover, 25k traces are needed for a successful key recoveries in case of polymorphism-based countermeasure [4].