Since 2010, I am a Cryptography & Security Expert for CryptoExperts in Paris !
I received a Ph.D. in 2008 under the direction of Prof. Serge Vaudenay, head of the Cryptography and Security Laboratory (LASEC) at EPFL, Switzerland. My main research areas cover block ciphers and their cryptanalysis. I then spent some time in Belgium where I worked as a consultant and researcher for Smals.
I am part of the program committee of the 2011 edition of the ECRYPT Workshop on Lightweight Cryptography.
LC 2011 is organized by the UCL Crypto Group and sponsored by the SymLab and VAMPIRE virtual labs of the Network of Excellence in Cryptology - ECRYPT II. It will be held on November 28-29, 2011, in Louvain-la-Neuve in Belgium.
In this paper, we study the soundness amplification by repetition of cryptographic protocols. As a tool, we use the Chernoff Information. We specify the number of attempts or samples required to distinguish two distributions efficiently in various protocols. This includes weakly verifiable puzzles such as CAPTCHA-like challenge-response protocols, interactive arguments in sequential composition scenario and cryptanalysis of block ciphers. As our main contribution, we revisit computational soundness amplification by sequential repetition in the threshold case, i.e when completeness is not perfect. Moreover, we outline applications to the Leftover Hash Lemma and iterative attacks on block ciphers.