Git hash function transition plan

Only have time to skim it, I didn&#x27;t see anyplace, so might be a good time to suggest multihash: <a href="https:&#x2F;&#x2F;multiformats.io&#x2F;multihash&#x2F;" rel="nofollow">https:&#x2F;&#x2F;multiformats.io&#x2F;multihash&#x2F;</a><p>Having git to use that could be a great opportunity to standardize on a de facto hash function encoding standard.<p>What would be the best way to suggest that (if it hasn&#x27;t been already, though I am guessing it likely has).

Funny, I always expected Git to transition by adding a stronger hash as a piece of metadata to each commit and continue using SHA-1 for the day-to-day identifier, seeing as most of the time Git doesn&#x27;t actually go back and actually <i>verify</i> the whole commit chain unless you ask it to.

Previous discussion: <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=13906804" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=13906804</a>

This doesn’t render very well on mobile. I wish the Git team would write their docs as a .md so GitHub could render as HTML with word wrap in all its glory.

So, this is the transition plan. Is there anywhere where we can find what progress has been made on the plan? As far as I can tell, it is only a plan at the moment?<p>I also like the idea of a transition plan, but is there anywhere a proposed timeframe, for phasing out the non &quot;post-transition&quot; modes of operation? That is, as an organisation, is there anything that we can do with this now towards our future planning?

So it says the protocol won&#x27;t be extended initially, only the repo format. I&#x27;m trying to figure out the implications of that. IIUC this basically boils down to: can we make sure that when you have a signed tag (i.e. a hash signed with GPG), the content of your repo is truly the same as what the signer intended, and not a collision generated by a bad actor.<p>It says that there will be a new format for signed objects, i.e. you will now be able to sign tags with NewHash. But if the format is not extended, does that mean you can&#x27;t get push or fetch those objects? If so then I believe this is just foundational work with no immediate functional impact, right?<p>(Not shitting on it btw, it&#x27;s obviously still a Good Idea!)

Torvald&#x27;s on signing commits : <a href="http:&#x2F;&#x2F;git.661346.n2.nabble.com&#x2F;GPG-signing-for-git-commit-td2582986.html" rel="nofollow">http:&#x2F;&#x2F;git.661346.n2.nabble.com&#x2F;GPG-signing-for-git-commit-t...</a>

The main downside to switching the hash function is that, when explaining why developers should stop worrying about hash conflicts, we&#x27;ll need to calculate a new analogy to replace the standard, 180 bit &quot;every member of your programming team being attacked and killed by wolves in unrelated incidents on the same night&quot; scenario.

&gt; Some hashes under consideration are SHA-256, SHA-512&#x2F;256, SHA-256x16, K12, and BLAKE2bp-256.

How does it prevent this exact same problem in the future?

&gt; In early 2005, around the time that Git was written, Xiaoyun Wang, &gt; Yiqun Lisa Yin, and Hongbo Yu announced an attack finding SHA-1 &gt; collisions in 2^69 operations. In August they published details. &gt; Luckily, no practical demonstrations of a collision in full SHA-1 were &gt; published until 10 years later, in 2017.<p>&gt; The hash function NewHash to replace SHA-1 should be stronger than &gt; SHA-1 was: we would like it to be trustworthy and useful in practice &gt; for at least 10 years.

Why is SHA-3 not explicitly mentioned as a candidate?

NewHash is a terrible name - on par with Xbox One [X] and iPad New. Googling stuff will be hard, and good luck explaining to less technical-savvy users what is this all about.<p>Plus, in 100 years, when SHA-256 is compromised, what would be the name of a <i>new</i> new format?

Can someone explain why they would transition to a new hash function and not a block chain based system of tracking? If one of the goals of introducing a stronger hash function is signage of individual commits it seems like a block chain would be ideal.