This book constitutes the refereed proceedings of the 7th International Conference on Cryptology and Network Security CANS 2008 held in Hong-Kong China in December 2008. The 27 revised full papers presented were carefully reviewed and selected from 73 submissions. The papers are organized in topical sections on cryptosystems signatures identification authentication and key management cryptographic algorithms and protocols stream ciphers and block ciphers cryptographic foundations applications and implementations as well as security in ad hoc networks and wireless sensor networks.