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Threefish
General
Designers Bruce Schneier, Niels Ferguson, Stefan Lucks, Doug Whiting, Mihir Bellare, Tadayoshi Kohno, Jon Callas, Jesse Walker
First published 2008
Cipher detail
Key sizes 256, 512 or 1024 bits
(key size is always block size)
Block sizes 256, 512 or 1024 bits
Rounds 72 (80 for 1024-bit block size)
Best public cryptanalysis
As of 2010, a rotational cryptanalysis attack against Threefish breaks:
  • 39 out of 72 rounds in Threefish-256
  • 42 out of 72 rounds in Threefish-512
  • 43.5 of 80 rounds in Threefish-1024

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;[1] 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.

Threefish and the Skein hash function were designed by Bruce Schneier, Niels Ferguson, Stefan Lucks, Doug Whiting, Mihir Bellare, Tadayoshi Kohno, Jon Callas, and Jesse Walker.

Contents

Security

In 2009, a related key boomerang attack against a reduced round Threefish version was published. For the 32-round version, the time complexity is 2226 and the memory complexity is 212; for the 33-round version, the time complexity is 2352.17 with a negligible memory usage. The attacks also work against the tweaked version of Threefish: for the 32-round version, the time complexity is 2222 and the memory complexity is 212; for the 33-round version, the time complexity is 2355.5 with a negligible memory usage.[2]

In 2010, a new rotational cryptanalysis attack was published against Threefish. The attack breaks 39 rounds out of 72 in Threefish-256, 42 of 72 in Threefish-512 and 43.5 out of 80 in Threefish-1024.[3][4]

See also

References

External links

  • "Homepage" Homepage of the Skein Hash Function Family.
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