Re: Questions about the hash function transition

From: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Date: Aug 23, 2018, 15:20 UTC
Message-ID: <876001f6u3.fsf@evledraar.gmail.com>
In-Reply-To: <xmqqy3cxjgz1.fsf@gitster-ct.c.googlers.com>

On Thu, Aug 23 2018, Junio C Hamano wrote:

Show 12 quoted lines

> Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:
>
>>> - The trailer consists of the following:
>>>   - A copy of the 20-byte SHA-256 checksum at the end of the
>>>     corresponding packfile.
>>>
>>>   - 20-byte SHA-256 checksum of all of the above.
>>
>> We need to update both of these to 32 byte, right? Or are we planning to
>> truncate the checksums?
>
> https://public-inbox.org/git/CA+55aFwc7UQ61EbNJ36pFU_aBCXGya4JuT-TvpPJ21hKhRengQ@mail.gmail.com/

Thanks.

Yeah for this checksum purpose even 10 or 5 characters would do, but since we'll need a new pack format anyway for SHA-256 why not just use the full length of the SHA-256 here? We're using the full length of the SHA-1.

I don't see it mattering for security / corruption detection purposes, but just to avoid confusion. We'll have this one place left where something looks like a SHA-1, but is actually a trunctated SHA-256.