Ever Better Cryptanalytic Results Against SHA-1
The SHA family (which, I suppose, should really be called the MD4 family) of cryptographic hash functions has been under attack for a long time. In 2005, we saw the first cryptanalysis of SHA-1 that was faster than brute force: collisions in 269 hash operations, later improved to 263 operations. A great result, but not devastating. But remember the great truism of cryptanalysis: attacks always get better, they never get worse. Last week, devastating got a whole lot closer. A new attack can, at least in theory, find collisions in 252 hash operations—well within the realm of computational possibility. Assuming the cryptanalysis is correct, we should expect to see an actual SHA-1 collision within the year.
Note that this is a collision attack, not a pre-image attack. Most uses of hash functions don’t care about collision attacks. But if yours does, switch to SHA-2 immediately. (This has more information on this, written for the 269 attack.)
This is why NIST is administering a SHA-3 competition for a new hash standard. And whatever algorithm is chosen, it will look nothing like anything in the SHA family (which is why I think it should be called the Advanced Hash Standard, or AHS).
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