Cryptography Seminar

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Marc Joye


Courbes elliptiques et attaques par canaux cach├ęs

Provable security becomes more and more popular in the cryptographic community. As exemplified by the NESSIE project, it is now common to see it as an attribute of a cryptosystem. Provable security is at the protocol level; a harder task may be to evaluate the security of a cryptosystem at the implementation level. Rather than considering a cryptosystem as a black-box, we may assume that some sensitive data can leak during the course of the execution of a (naively implemented) crypto-algorithm. A concrete example is given by the so-called side-channel analysis.

Side-channel analysis is a powerful technique re-discovered by P. Kocher in 1996. The principle consists in monitoring some side-channel information like the running time, the power consumption, or the electromagnetic radiation. Next, from the monitored data, the attacker tries to deduce the inner-workings of the algorithm and thereby to retrieve some secret information. When there is a single measurement, the process is referred to as a simple side-channel analysis; and when there are several measurements handled together with statistical tools, the process is referred to as differential side-channel analysis.

This talk is aimed at studying the resistance of elliptic curve cryptosystems against those two classes of attacks. In particular, we survey the various strategies proposed so far to prevent side-channel attacks.