This post misses, uh, a few important things that get mentioned in the lobsters comments: https://lobste.rs/s/bytzgl/git_3_0_s_upcoming_sha_256_default_will_be

It's sad to see this community only listening to people because they're rich: there are a lot of better engineers who knows more than this guy but they're not "co-creator of GitHub". I read this title as boot licking silicon valley.

That being said you don't hash git commits for security reason : YOU SIGN YOUR COMMITS FOR SECURITY. Sorry for the caps but let's make this visible.

His defense of SHA-1:

Mathematically, for SHA-1’s 160-bit output, the birthday bound means that you would need about 1.4 septillion random files (1.4 quadrillion billion files - 1,400,000,000,000,000 billion - it's impossible to effectively describe) in a single project to have file hashes accidentally collide.

For the most part the article mostly talks about collision attacks, which quite frankly i think is silly.

He also talks about hashes pointing to other (older) projects using a different hashing algorithm, but can't the software just detect if its a SHA-1 hash or SHA-256, and fetch it accordingly? He acts like its the end of the world when in my mind most everything can (and probably will) be compensated for pretty easily. It's reminiscent of the IPv6 fear-mongering.

The thing that gets me is he doesn't say if the current hashing algorithm or the new one has any support for when hashes do collide. Since that can theoretically happen with both, to me that sounds like a problem worth tackling.

Madness

We had a similar stupid issue at my last job. Someone made an edict that all Sha-1 and md5 references in the code must be removed for security reasons.

Why did they skip the 255 versions?!

/s

I'm not qualified to talk about it but Hacker News has arguments against his post: https://news.ycombinator.com/item?id=49924179

I pull it from there because I trust that GitHub has its authentication game together enough that it's unlikely that anyone malicious...

i don't. more importantly, my package manager doesn't. that is, every package manager i can think of references git commit hashes in its build system. the end user trusts that when they build from commit xxxxxxxx, they're getting the exact same code as everyone else. what exactly is being signed in these build systems i don't know, but whatever scott or linus or anyone else wishes would happen, in the real world, commit hashes are a part of the trust chain.

then again, a lot of package managers just use tags. so maybe in practice, they do trust microsoft.

There's people who seriously think commit hashes are there for security purposes? Furthermore, there are git MAINTAINERS that think this?

How absurd. Author is completely right, making SHA-256 the default implementation serves no purpose. SHA-1 is a completely valid algorithm for non-security use cases, which is precisely how git uses it. This is a solution looking for a problem.

I think he's maybe overblowing the impact of this change. Realistically, the only ones who are going to be impacted are the folks who maintain git-related tools and forges, as he mentions. The rest of us probably won't even notice. But that's still a ton of pointless work for those folks.