Starting to think about sha-256?
From: Jeff Garzik <hidden>
Date: 2016-06-15 22:42:38
Recent press[1] is talking about sha-1 collisions again. Even though the reported attack was against a weakened variant of sha-1 (64, not 80, passes), it serves as a useful point to start talking about the future. I argue that sha-256 is better suited to git's purposes, and to modern machines, than sha-1. Upsides to sha-256: * not just a bit increase, but a stronger algorithm. there is more mixing, doing a more-than-incrementally better job at avoiding collisions. * the bit increase itself provides more hash space, theoretically reducing collisions. * properly aligned, a set of 32-byte hashes won't straddle CPU cachelines. Downsides to sha-256: * git protocol/storage format change implications. * increase in storage size (20 to 32 bytes per hash). * fewer hand-optimized algorithm variants have been implemented. * likely more CPU cycles per hash, though I haven't measured. Wikimedia page has lotsa info: http://en.wikipedia.org/wiki/Secure_Hash_Algorithm Maybe sha-256 could be considered for the next major-rev of git? Jeff [1] http://www.heise-security.co.uk/news/77244