Re:Whatever happened to SHA-256 support in Git?
by dspillett on Thursday June 23, 2022 @03:58PM
(#31854407)
It makes random collisions more likely when comparing truncated SHA256 to pure SHA256, but given the collisions and pre-image attacks shown so far is truncated SHA256 still safer than SHA1 in that respect? I have seen an article that claimed so (sorry, I can't re-find it ATM so I can't offer it for criticism, if anyone else has good information either way please respond with relevant links), and it is immune to extension attacks which is a significant advantage if this is part of your threat sensitivity surface and SHA1 is used without other protective wrappers like HMAC.
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Re:Whatever happened to SHA-256 support in Git?
by bawolff on Thursday June 23, 2022 @04:44PM
(#31854909)
Truncated sha256 is safer than sha-1 (depending of course on how much you truncate it, but given context lets assume truncating to size of sha-1 - 160 bits).
SHA-1 is quite broken at this point. SHA-256 is not. There aren't any practical non-generic attacks on full sha-256 and thus there wouldn't be any on the truncated version. The Wikipedia article goes into the different attacks on the two algorithms.
That said, if your concern is length extension attacks - strongly reccomend using sha-512/256 instead of trying to do your own custom thing.