Tiger: a fast new hash function. Among those cryptographic hash function which are not based on block ciphers, MD4 and Snefru seemed initially quite attractive for applications requiring fast software hashing. However collisions for Snefru were found in 1990, and recently a collision of MD4 was also found. This casts doubt on how long these functions’ variants, such as RIPE-MD, MD5, SHA, SHA1 and Snefru-8, will remain unbroken. Furthermore, all these functions were designed for 32-bit processors, and cannot be implemented efficiently on the new generation of 64-bit processors such as the DEC Alpha. We therefore present a new hash function which we believe to be secure; it is designed to run quickly on 64-bit processors, without being too slow on existing machines.