Cryptology ePrint Archive: Report 2005/243

Cryptanalysis of Sfinks

Nicolas T. Courtois

Abstract: Sfinks is an LFSR-based stream cipher submitted to ECRYPT call for stream ciphers by Braeken, Lano, Preneel et al. The designers of Sfinks do not to include any protection against algebraic attacks. They rely on the so called "Algebraic Immunity", that relates to the complexity of a simple algebraic attack, and ignores other algebraic attacks. As a result, Sfinks is insecure.

Category / Keywords: secret-key cryptography / algebraic cryptanalysis, stream ciphers, nonlinear filters, Boolean functions, solving systems of multivariate equations, fast algebraic attacks on stream ciphers

Date: received 24 Jul 2005, last revised 31 Jul 2005

Contact author: courtois at minrank org

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Version: 20050731:200244 (All versions of this report)

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