Re: Questions about the hash function transition

From: Jonathan Nieder <jrnieder@gmail.com>
Date: Aug 24, 2018, 01:54 UTC
Message-ID: <20180824015438.GF99542@aiede.svl.corp.google.com>
In-Reply-To: <20180824014007.GF535143@genre.crustytoothpaste.net>

Hi,

brian m. carlson wrote:

> On Thu, Aug 23, 2018 at 04:02:51PM +0200, Ævar Arnfjörð Bjarmason wrote:

Show 8 quoted lines

>>> 1. Add SHA-256 support to Git protocol. This is valuable and the
>>>    logical next step but it is out of scope for this initial design.
>>
>> This is a non-goal according to the docs, but now that we have protocol
>> v2 in git, perhaps we could start specifying or describing how this
>> protocol extension will work?
>
> I have code that does this.  The reason is that the first stage of the

[nice explanation snipped]

> I hope to be able to spend some time documenting this in a little bit.
> I have documentation for that code in my branch, but I haven't sent it
> in yet.

Yay!

> I realize I have a lot of code that has not been sent in yet, but I also
> tend to build on my own series a lot, and I probably need to be a bit
> better about extracting reusable pieces that can go in independently
> without waiting for the previous series to land.

For what it's worth, even if it all is in one commit with message "wip", I think I'd benefit from being able to see this code. I can promise not to critique it, and to only treat it as a rough premonition of the future.

[...]

> For SHA-1, I have 0x73686131, which is "sha1", big-endian, and for
> SHA-256, I have 0x73323536, which is "s256", big-endian.  The former is
> in the codebase already; the latter, in my hash-impl branch.

I mentioned in another reply that "sha2" sounds fine. "s256" of course also sounds fine to me. Thanks to Ævar for asking so that we have the reminder to pin it down in the doc.

Thanks, Jonathan