The Skein hash family is a group of cryptographic hash functions which entered the final round of the NIST SHA-3 competition, it ultimately lost to Keccak. Developed by Niels Ferguson, Bruce Schneier, Stefan Lucks, Doug Whiting, Mihir Bellare, Tadayoshi Kohno, Jon Callas, and Jesse Walker, Skein incorporates the Threefish block cipher as its core building block.

The version 1.3 paper by Niels Ferguson, et al. is available at https://www.schneier.com/wp-content/uploads/2015/01/skein.pdf. The original website has since been dismantled.