Re: Hash algorithm analysis

From: Junio C Hamano <gitster@pobox.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Edward Thomson <ethomson@edwardthomson.com>,
	"brian m. carlson" <sandals@crustytoothpaste.net>,
	Jonathan Nieder <jrnieder@gmail.com>,
	Git Mailing List <git@vger.kernel.org>,
	Johannes Schindelin <Johannes.Schindelin@gmx.de>,
	demerphq <demerphq@gmail.com>, Adam Langley <agl@google.com>,
	keccak@noekeon.org
Subject: Re: Hash algorithm analysis
Date: Tue, 24 Jul 2018 14:13:07 -0700	[thread overview]
Message-ID: <xmqqzhygwd5o.fsf@gitster-ct.c.googlers.com> (raw)
In-Reply-To: <CA+55aFwSe9BF8e0hLk9pp3FVD5LaVY5GRdsV3fbNtgzekJadyA@mail.gmail.com> (Linus Torvalds's message of "Tue, 24 Jul 2018 13:31:00 -0700")

Linus Torvalds <torvalds@linux-foundation.org> writes:

> On Tue, Jul 24, 2018 at 12:01 PM Edward Thomson
> <ethomson@edwardthomson.com> wrote:
>>
>> Switching gears, if I look at this from the perspective of the libgit2
>> project, I would also prefer SHA-256 or SHA3 over blake2b.  To support
>> blake2b, we'd have to include - and support - that code ourselves.  But
>> to support SHA-256, we would simply use the system's crypto libraries
>> that we already take a dependecy on (OpenSSL, mbedTLS, CryptoNG, or
>> SecureTransport).
>
> I think this is probably the single strongest argument for sha256.
> "It's just there".

Yup.  I actually was leaning toward saying "all of them are OK in
practice, so the person who is actually spear-heading the work gets
to choose", but if we picked SHA-256 now, that would not be a choice
that Brian has to later justify for choosing against everybody
else's wishes, which makes it the best choice ;-)