Nicolas Tadeusz Courtois (born 14 November 1971) is a cryptographer.
He was formerly senior lecturer in computer science at University College London.
[2] Courtois was one of the co-authors of both the XSL attack against block ciphers, such as the Advanced Encryption Standard,[3][4] and the XL system for solving systems of algebraic equations[5] used in the attack.
Other cryptographic results of Courtois include algebraic attacks on stream ciphers,[6] attacks on the KeeLoq and Hitag 2 systems used for remote keyless automobile entry systems,[7] and an analysis of cryptographic weaknesses in public transit smart cards including the London Underground Oyster card[8] and the Dutch OV-chipkaart.
[10] Courtois graduated from University of Paris VI: Pierre et Marie Curie, where he received his doctoral degree in cryptography.