SHA-1 Broken

SHA-1 Broken.

SHA-1 has been broken. Not a reduced-round version. Not a simplified version. The real thing.

The research team of Xiaoyun Wang, Yiqun Lisa Yin, and Hongbo Yu
(mostly from Shandong University in China) have been quietly
circulating a paper announcing their results:

  • collisions in the the full SHA-1 in 2**69 hash operations, much
    less than the brute-force attack of 2**80 operations based on the hash

  • collisions in SHA-0 in 2**39 operations.

  • collisions in 58-round SHA-1 in 2**33 operations.

This attack builds on previous attacks on SHA-0 and SHA-1, and is a
major, major cryptanalytic result. This pretty much puts a bullet into
SHA-1 as a hash function for digital signatures (although it doesn't
affect applications such as HMAC).

The paper isn't generally available yet. At this point I can't tell
if the attack is real, but the paper looks good and this is a reputable
research team.

More details when I have them.   [Schneier on Security]

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