On 3/9/22 04:48, Daniel P. Berrangé wrote: > On Wed, Mar 09, 2022 at 10:44:28AM +0100, Miroslav Lichvar wrote: >> On Tue, Mar 08, 2022 at 07:40:15PM +0100, Alexander Sosedkin wrote: >>> Took git years to migrate from SHA-1, and some others haven't even started. >> >> git is a good example showing that this won't be easy. The SHA-256 >> object format is still marked as experimental and not the default. > > Unless I'm mistaken Git isn't using SHA1 in cryptographic signatures, > it is using it directly for hashing. The proposal isn't banning all > use of SHA1, just SHA-1 based signatures. Git *does* use SHA-1 in signatures, via signed Git tags and commits. However, Git also includes code that can detect all known relatively fast collision attacks on SHA-1. A brute force attack (with 2^80 time complexity) is still possible, but the amount of resources required is such that the attack is not considered likely. Furthermore, in many cases, one would not only need to find a collision in SHA-1, but also get one of the colliding objects past code review. Finding a collision that will pass code review is likely far, *far* more difficult than just finding a collision. In short, Git *does* need to move away from SHA-1, but it isn’t a crisis — yet. -- Sincerely, Demi Marie Obenour (she/her/hers)
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