Séminaire de Cryptographie

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François-Xavier Standaert

Recent results about side-channel attacks and countermeasures.

Traditionally, cryptographic algorithms provide security against an adversary who has only black box access to cryptographic devices. That is, the only thing the adversary can do is to query the cryptographic algorithm on inputs of its choice and analyze the responses, which are always computed according to the correct original secret information. However, such a model does not always correspond to the realities of physical implementations. During the last decade, significant attention has been paid to the physical security evaluation of cryptographic devices. In particular, it has been demonstrated that actual attackers may be much more powerful than what is captured by the black box model. For example, they can actually get a side-channel information, based on the device's physical computational steps. As a consequence, some kind of obfuscation is required to protect integrated circuits from these physical attacks. This is especially important for small embedded devices (e.g. smart card, RFIDs, sensor networks, ...) that can typically be under and adversary's control for a short period of time. This implies new theoretical concerns (how to exactly model and evaluate these physical threats) and practical ones (how to prevent them). In this talk, I will discuss different results in the area of side-channel attacks, with a particular focus on formal tools that can be used to evaluate physical security on a fair basis. Starting from an introductive view of the field, I will describe some well known attacks and countermeasures, present a framework for the analysis of side-channel key-recovery from Eurocrypt 2009 and finally discuss the connection of this framework with recent works in leakage-resilient cryptography.