Worst-case side-channel security : from evaluation of countermeasures to new designs

Modern cryptography relies on the Kerckhoff’s principle which states that everything about a crypto-system should be public, except for the secret keys. In this thesis, I apply these principles to cryptography implementations by providing the evaluator full knowledge of the implementation, in a worst-case manner. As a result, it allows to estimate their long-term security against side-channel attacks. The first part is dedicated to the verification of the two underlying assumptions in masking proofs. More precisely, I contribute to proof-based evaluations by putting forward that i) the verification of independence thanks to leakage detection benefits from multivariate statistics ii) the noise can be estimated in a quantitative manner thanks to formal bounds on the mutual information. The second part of the thesis is dedicated to efficient methodologies to perform worst-case attacks which are a useful shortcut for evaluators since they allow to estimate, with a reduce profiling data complexity, the online complexity other attacks strategies. Concretely, I propose worst-case attacks against a recent open-source AES implementation by the French ANSSI and masked higher-order bitslice implementations. From the lessons learned from the side-channel evaluation of current proposals, I propose new designs to obtain strong side-channel protection. More precisely, the noise versus security trade-off can be improved thanks to a sound combination of masking and shuffling. Concretely, I apply masking and shuffling to ISW multiplications in order to exponentially amplify with masking the effect of shuffling.