This book constitutes the refereed proceedings of the Second Theory of Cryptography Conference, TCC 2005, held in Cambridge, MA, USA in February 2005.

The 32 revised full papers presented were carefully reviewed and selected from 84 submissions. The papers are organized in topical sections on hardness amplification and error correction, graphs and groups, simulation and secure computation, security of encryption, steganography and zero knowledge, secure computation, quantum cryptography and universal composability, cryptographic primitives and security, encryption and signatures, and information theoretic cryptography.