Template:Primary sources Template:Infobox block cipher Threefish is a tweakable block cipher designed as part of the Skein hash function, an entry in the NIST hash function competition. Threefish uses no S-boxes or other table lookups in order to avoid cache timing attacks; its nonlinearity comes from alternating additions with exclusive ORs. In that respect, it's similar to Salsa20, TEA, and the SHA-3 candidates CubeHash and BLAKE.
In October 2010, an attack that combines rotational cryptanalysis with the rebound attack was published. The attack breaks collision resistance within 53 of 72 rounds in Threefish-256, and 57 of 72 rounds in Threefish-512. It also affects the Skein hash function. This is a follow-up to the earlier attack published in February, which breaks 39 and 42 rounds respectively.
In 2009, a related key boomerang attack against a reduced round Threefish version was published. For the 32-round version, the time complexity is and the memory complexity is ; for the 33-round version, the time complexity is with a negligible memory usage. The attacks also work against the tweaked version of Threefish: for the 32-round version, the time complexity is and the memory complexity is ; for the 33-round version, the time complexity is with a negligible memory usage.
- "Homepage" Homepage of the Skein Hash Function Family.