This book constitutes the refereed proceedings of the 4th Theory of Cryptography Conference, TCC 2007, held in Amsterdam, The Netherlands in February 2007.
The 31 revised full papers presented were carefully reviewed and selected from 118 submissions. The papers are organized in topical sections on encryption, universally composable security, arguments and zero knowledge, notions of security, obfuscation, secret sharing and multiparty computation, signatures and watermarking, private approximation and black-box reductions, and key establishment.