FORK-256

FORK-256 is a hash algorithm designed in response to security issues discovered in the earlier SHA-1 and MD5 algorithms. After substantial cryptanalysis, the algorithm is considered broken.

Background

In 2005, Xiaoyun Wang announced an order-collision attack on the government's hash standard SHA-1. The National Institute of Standards and Technology (NIST), the body responsible for setting cryptographic standards in the United States, concluded this was a practical attack (as previous estimates were order-) and began encouraging additional research into hash functions and their weaknesses. As part of this effort, NIST hosted two workshops where potential new algorithms, including FORK-256, were introduced and discussed. Rather than immediately select any of these algorithms, NIST conducted a public competition from 2007–2012 which ultimately resulted in the Keccak algorithm being selected for use as the SHA-3 standard.

Algorithm and Analysis

FORK-256 was introduced at the 2005 NIST Hash workshop and published the following year. FORK-256 uses 512-bit blocks and implements preset constants that change after each repetition. Each block is hashed into a 256-bit block through four branches that divides each 512 block into sixteen 32-bit words that are further encrypted and rearranged.