Description:This book constitutes the thoroughly refereed post-proceedings of the 12th International Workshop on Fast Software Encryption, FSE 2005, held in Paris, France in February 2005.The 29 revised full papers presented were carefully reviewed and selected from 96 submissions. The papers address all current aspects of fast primitives for symmetric cryptology, including the design, cryptanalysis, and implementation of block ciphers, stream ciphers, hash functions, and message authentication codes.