Multivariate multitarget high order side-channel attacks

Side Channel Attacks are a classical threat against cryptographic algorithms in embedded systems. They aim at exploiting the physical leakages unintentionally emitted by the devices during the execution of their embedded programs to recover sensitive data. As such attacks represent a real threat against embedded systems different countermeasures have been developed. In thesis we investigate their security in presence of multiple leakages. Indeed there often are in the leakage measurements several variables which can be exploited to mount Side Channel Attacks. In particular we show in this thesis the optimal way to exploit multiple leakages of a unique variable. This dimensionality reduction comes with no loss on the overall exploitable information. Based on this result we investigate further how such dimensionality reduction methodscan be applied in the case of protected implementations. We show that the impact of such methods increases with the security “level” of the implementation. We also investigate how to exploit the leakages of multiplevariables in order to improve the results of Side Channel Analysis. We start by improving the attacks against masking schemes, with a precomputed table recomputation step. Some protections have been developed to protect such schemes. As a consequence we investigate the security provided by these protections. In this context we present results which show that the main parameter to evaluate the security of the masking schemes is not sufficient to estimate the global security of the implementation. Finally we show that in the context of masking scheme with shuffling the optimal attack is not computable. As a consequence we present a truncated version of this attack with a better effectiveness.