This book constitutes the refereed proceedings of the Third International Information Security Practice and Experience Conference, ISPEC 2007, held in Hong Kong, China in May 2007. The 24 revised full papers presented together with 2 invited papers were carefully reviewed and selected from 135 submissions. The papers are organized in topical sections on cryptanalysis, signatures, network security and security management, privacy and applications, cryptographic algorithms and implementations, authentication and key management, as well as cryptosystems.