This book constitutes the refereed proceedings of the Cryptographers' Track at the RSA Conference 2003, CT-RSA 2003, held in San Francisco, CA, USA, in April 2003. The 26 revised full papers presented together with abstracts of 2 invited talks were carefully reviewed and selected from 97 submissions. The papers are organized in topical sections on key self-protection, message authentication, digital signatures, pairing based cryptography, multivariate and lattice problems, cryptographic architectures, new RSA-based cryptosystems, chosen-ciphertext security, broadcast encryption and PRF sharing, authentication structures, elliptic curves and pairings, threshold cryptography, and implementation issues.