From: Junio C Hamano <gitster@pobox.com>
To: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Cc: git@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>,
Edward Thomson <ethomson@edwardthomson.com>,
"brian m . carlson" <sandals@crustytoothpaste.net>,
Jonathan Nieder <jrnieder@gmail.com>,
Johannes Schindelin <Johannes.Schindelin@gmx.de>,
demerphq <demerphq@gmail.com>, Adam Langley <agl@google.com>,
keccak@noekeon.org
Subject: Re: [PATCH 2/2] doc hash-function-transition: pick SHA-256 as NewHash
Date: Wed, 25 Jul 2018 09:45:52 -0700 [thread overview]
Message-ID: <xmqq4lgnw9fj.fsf@gitster-ct.c.googlers.com> (raw)
In-Reply-To: <20180725083024.16131-3-avarab@gmail.com> ("Ævar Arnfjörð Bjarmason"'s message of "Wed, 25 Jul 2018 08:30:24 +0000")
Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:
> @@ -125,19 +122,19 @@ Detailed Design
> ---------------
> Repository format extension
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~
> -A NewHash repository uses repository format version `1` (see
> +A SHA-256 repository uses repository format version `1` (see
> Documentation/technical/repository-version.txt) with extensions
> `objectFormat` and `compatObjectFormat`:
>
> [core]
> repositoryFormatVersion = 1
> [extensions]
> - objectFormat = newhash
> + objectFormat = sha256
> compatObjectFormat = sha1
Whenever we said SHA1, somebody came and told us that the name of
the hash is SHA-1 (with dash). Would we be nitpicker-prone in the
same way with "sha256" here?
> @@ -155,36 +152,36 @@ repository extensions.
> Object names
> ~~~~~~~~~~~~
> Objects can be named by their 40 hexadecimal digit sha1-name or 64
> -hexadecimal digit newhash-name, plus names derived from those (see
> +hexadecimal digit sha256-name, plus names derived from those (see
> gitrevisions(7)).
Seeing this hunk makes me respond to the above question with another
question: "having to write sha-256-name, sha-1-name, gpgsig-sha-256,
and sha-256-content is sort of ugly, no?"
I guess names with two dashes are not _too_ bad, so I dunno.
> Selection of a New Hash
> -----------------------
> @@ -611,6 +608,10 @@ collisions in 2^69 operations. In August they published details.
> Luckily, no practical demonstrations of a collision in full SHA-1 were
> published until 10 years later, in 2017.
>
> +It was decided that Git needed to transition to a new hash
> +function. Initially no decision was made as to what function this was,
> +the "NewHash" placeholder name was picked to describe it.
> +
> The hash function NewHash to replace SHA-1 should be stronger than
> SHA-1 was: we would like it to be trustworthy and useful in practice
> for at least 10 years.
This sentence needs a bit of updating to match the new paragraph
inserted above. "should be stronger" is something said by those
who are still looking for one and/or trying to decide. Perhaps
something like this?
...
the "NewHash" placeholder name was used to describe it.
We wanted to choose a hash function to replace SHA-1 that is
stronger than SHA-1 was, and would like it to be trustworthy
and useful in practice for at least 10 years.
Some other relevant properties we wanted in NewHash are:
> @@ -630,14 +631,19 @@ Some other relevant properties:
> 4. As a tiebreaker, the hash should be fast to compute (fortunately
> many contenders are faster than SHA-1).
>
> -Some hashes under consideration are SHA-256, SHA-512/256, SHA-256x16,
> +Some hashes under consideration were SHA-256, SHA-512/256, SHA-256x16,
> K12, and BLAKE2bp-256.
>
> +Eventually in July 2018 SHA-256 was chosen to be the NewHash. See the
> +thread starting at <20180609224913.GC38834@genre.crustytoothpaste.net>
> +for the discussion
> +(https://public-inbox.org/git/20180609224913.GC38834@genre.crustytoothpaste.net/)
> +
next prev parent reply other threads:[~2018-07-25 16:45 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-09 20:56 State of NewHash work, future directions, and discussion brian m. carlson
2018-06-09 21:26 ` Ævar Arnfjörð Bjarmason
2018-06-09 22:49 ` Hash algorithm analysis brian m. carlson
2018-06-11 19:29 ` Jonathan Nieder
2018-06-11 20:20 ` Linus Torvalds
2018-06-11 23:27 ` Ævar Arnfjörð Bjarmason
2018-06-12 0:11 ` David Lang
2018-06-12 0:45 ` Linus Torvalds
2018-06-11 22:35 ` brian m. carlson
2018-06-12 16:21 ` Gilles Van Assche
2018-06-13 23:58 ` brian m. carlson
2018-06-15 10:33 ` Gilles Van Assche
2018-07-20 21:52 ` brian m. carlson
2018-07-21 0:31 ` Jonathan Nieder
2018-07-21 19:52 ` Ævar Arnfjörð Bjarmason
2018-07-21 20:25 ` brian m. carlson
2018-07-21 22:38 ` Johannes Schindelin
2018-07-21 23:09 ` Linus Torvalds
2018-07-21 23:59 ` brian m. carlson
2018-07-22 9:34 ` Eric Deplagne
2018-07-22 14:21 ` brian m. carlson
2018-07-22 14:55 ` Eric Deplagne
2018-07-26 10:05 ` Johannes Schindelin
2018-07-22 15:23 ` Joan Daemen
2018-07-22 18:54 ` Adam Langley
2018-07-26 10:31 ` Johannes Schindelin
2018-07-23 12:40 ` demerphq
2018-07-23 12:48 ` Sitaram Chamarty
2018-07-23 12:55 ` demerphq
2018-07-23 18:23 ` Linus Torvalds
2018-07-23 17:57 ` Stefan Beller
2018-07-23 18:35 ` Jonathan Nieder
2018-07-24 19:01 ` Edward Thomson
2018-07-24 20:31 ` Linus Torvalds
2018-07-24 20:49 ` Jonathan Nieder
2018-07-24 21:13 ` Junio C Hamano
2018-07-24 22:10 ` brian m. carlson
2018-07-30 9:06 ` Johannes Schindelin
2018-07-30 20:01 ` Dan Shumow
2018-08-03 2:57 ` Jonathan Nieder
2018-09-18 15:18 ` Joan Daemen
2018-09-18 15:32 ` Jonathan Nieder
2018-09-18 16:50 ` Linus Torvalds
2018-07-25 8:30 ` [PATCH 0/2] document that NewHash is now SHA-256 Ævar Arnfjörð Bjarmason
2018-07-25 8:30 ` [PATCH 1/2] doc hash-function-transition: note the lack of a changelog Ævar Arnfjörð Bjarmason
2018-07-25 8:30 ` [PATCH 2/2] doc hash-function-transition: pick SHA-256 as NewHash Ævar Arnfjörð Bjarmason
2018-07-25 16:45 ` Junio C Hamano [this message]
2018-07-25 17:25 ` Jonathan Nieder
2018-07-25 21:32 ` Junio C Hamano
2018-07-26 13:41 ` [PATCH v2 " Ævar Arnfjörð Bjarmason
2018-08-03 7:20 ` Jonathan Nieder
2018-08-03 16:40 ` Junio C Hamano
2018-08-03 17:01 ` Linus Torvalds
2018-08-03 16:42 ` Linus Torvalds
2018-08-03 17:43 ` Ævar Arnfjörð Bjarmason
2018-08-04 8:52 ` Jonathan Nieder
2018-08-03 17:45 ` brian m. carlson
2018-07-25 22:56 ` [PATCH " brian m. carlson
2018-06-11 21:19 ` Hash algorithm analysis Ævar Arnfjörð Bjarmason
2018-06-21 8:20 ` Johannes Schindelin
2018-06-21 22:39 ` brian m. carlson
2018-06-11 18:09 ` State of NewHash work, future directions, and discussion Duy Nguyen
2018-06-12 1:28 ` brian m. carlson
2018-06-11 19:01 ` Jonathan Nieder
2018-06-12 2:28 ` brian m. carlson
2018-06-12 2:42 ` Jonathan Nieder
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