This book constitutes the refereed proceedings of the First International Conference on Cryptology hosted in Malaysia, held in Kuala Lumpur, Malaysia in September 2005, in conjunction with the e-Secure Malaysia 2005 convention. The 19 revised full papers presented together with 3 invited papers were carefully reviewed and selected from a total of 90 submissions. The papers are organized in topical sections on stream ciphers analysis, cryptography based on combinatorics, cryptographic protocols, implementation issues, unconventional cryptography, block cipher cryptanalysis, and homomorphic encryption.