This book constitutes the thoroughly refereed post-proceedings of the 11th International Workshop on Selected Areas in Cryptography, SAC 2004, held in Waterloo, Canada in August 2004.

The 24 revised full papers presented were carefully selected during two rounds of reviewing and improvement. The papers are organized in topical sections on stream cipher analysis, side channel analysis, block cipher design, efficient implementations, secret key cryptography, cryptanalysis, and cryptographic protocols.