Séminaire SoSySec

Sécurité des logiciels et des systèmes

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Tania Richmond (Université de Toulon)

Side-channel analysis in code-based cryptography

The first cryptographic protocol based on error-correcting codes was proposed in 1978 by Robert McEliece. Code-based cryptography is called post-quantum because until now, no algorithm able to attack this kind of protocols in polynomial time, even using a quantum computer, has been proposed. This is in contrast with protocols based on number theory problems like factorization of large numbers, for which efficient Shor's algorithm can be used on quantum computers.

Nevertheless, the McEliece cryptosystem security is based not only on mathematical problems. Implementation, in software or hardware, is also very important for its security. Improvements regarding its side-channel analysis can still be done.

We present two attacks against the McEliece cryptosystem in decryption, used with classical Goppa codes. Proposed attacks are based on evaluation of running time for the first one, and on power consumption analysis for the second one. We provide associate countermeasures and show that it is necessary to secure the decryption algorithm by considering it as a whole and not only step by step.