This book constitutes the refereed proceedings of the Cryptographers' Track at the RSA Conference 2006, CT-RSA 2006, held in San Jose, CA, USA in February 2006. The 22 revised full papers presented together with 2 invited papers were carefully reviewed and selected from 72 submissions. The papers are organized in topical sections on attacks on AES, identification, algebra, integrity, public key encryption, signatures, side-channel attacks, CCA encryption, message authentication, block ciphers, and multi-party computation.