Sécurité des cryptosystèmes contre les attaques par analyse de courant
Sonia Belaïd · HAL (Le Centre pour la Communication Scientifique Directe) · 2015
Side-channel attacks are the most efficient attacks against cryptosystems. While the classical black-box attacks only exploit the inputs and outputs of cryptographic algorithms, side-channel attacks also use the physical leakage released by the underlying device during algorithms executions. In this thesis, we focus on one kind of side-channel attacks which exploits the power consumption of the underlying device to recover the algorithms secret keys : power-analysis attacks.Most of the existing power-analysis attacks rely on the observations of variables which only depend on a few secret bits using a divide-and-conquer strategy. In this thesis, we exhibit new kinds of attacks which exploit the observation of intermediate variables highly dependent onhuge secrets. We also study two commonly used algorithmic countermeasures against side-channel attacks : leakage-resilient primitives and masking schemes. On the one hand, we define a leakage-resilient encryption scheme based on a regular update of the secret key and we prove its security. On the other hand, we build, using formal methods, a tool to automatically verify the security of masked algorithms.We also exhibit new security and compositional properties which can be used to generate masked algorithms at any security order from their unprotected versions. Finally, we propose a comparison between these two countermeasures in order to help industrial experts to determine the best protection to integrate in their products.