This book constitutes the thoroughly refereed post-proceedings of the 13th International Workshop on Security Protocols, held in Cambridge, UK, in April 2005. There are 24 revised full papers presented together with edited transcriptions of some of the discussions following the presentations. Among the topics addressed are authentication, anonymity, cryptographics and biometrics, cryptographic protocols, network security, privacy, SPKI, user-friendliness, and access control.