This book constitutes the thoroughly refereed post-conference proceedings of the 21st International Workshop on Fast Software Encryption, held in London, UK, March 3-5, 2014. The 31 revised full papers presented were carefully reviewed and selected from 99 initial submissions. The papers are organized in topical sections on designs; cryptanalysis; authenticated encryption; foundations and theory; stream ciphers; hash functions; advanced constructions.

Designs.- Cryptanalysis.- Authenticated encryption.- Foundations and theory.- Stream ciphers.- Hash functions.- Advanced constructions.