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From: "brian m. carlson" <sandals@crustytoothpaste.net>
To: Jonathan Nieder <jrnieder@gmail.com>
Cc: Ævar Arnfjörð Bjarmason <avarab@gmail.com>,
	git@vger.kernel.org, Junio C Hamano <gitster@pobox.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Edward Thomson <ethomson@edwardthomson.com>,
	Johannes Schindelin <Johannes.Schindelin@gmx.de>,
	demerphq <demerphq@gmail.com>, Adam Langley <agl@google.com>,
	keccak@noekeon.org
Subject: Re: [PATCH v2 2/2] doc hash-function-transition: pick SHA-256 as NewHash
Date: Fri, 3 Aug 2018 17:45:58 +0000
Message-ID: <20180803174558.GC106068@genre.crustytoothpaste.net> (raw)
In-Reply-To: <20180803072014.GA256410@aiede.svl.corp.google.com>

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On Fri, Aug 03, 2018 at 12:20:14AM -0700, Jonathan Nieder wrote:
> Ævar Arnfjörð Bjarmason wrote:
> >  Object format
> >  ~~~~~~~~~~~~~
> >  The content as a byte sequence of a tag, commit, or tree object named
> > -by sha1 and newhash differ because an object named by newhash-name refers to
> > +by sha1 and sha256 differ because an object named by sha256-name refers to
> 
> Not about this patch: this should say SHA-1 and SHA-256, I think.
> Leaving it as is in this patch as you did is the right thing.
> 
> [...]
> > @@ -255,10 +252,10 @@ network byte order):
> >    up to and not including the table of CRC32 values.
> >  - Zero or more NUL bytes.
> >  - The trailer consists of the following:
> > -  - A copy of the 20-byte NewHash checksum at the end of the
> > +  - A copy of the 20-byte SHA-256 checksum at the end of the
> 
> Not about this patch: a SHA-256 is 32 bytes.  Leaving that for a
> separate patch as you did is the right thing, though.
> 
> [...]
> > -  - 20-byte NewHash checksum of all of the above.
> > +  - 20-byte SHA-256 checksum of all of the above.
> 
> Likewise.

For the record, my code for these does use 32 bytes.  I'm fine with this
being a separate patch, though.

> [...]
> > @@ -351,12 +348,12 @@ the following steps:
> >     (This list only contains objects reachable from the "wants". If the
> >     pack from the server contained additional extraneous objects, then
> >     they will be discarded.)
> > -3. convert to newhash: open a new (newhash) packfile. Read the topologically
> > +3. convert to sha256: open a new (sha256) packfile. Read the topologically
> 
> Not about this patch: this one's more murky, since it's talking about
> the object names instead of the hash function.  I guess "sha256"
> instead of "SHA-256" for this could be right, but I worry it's going
> to take time for me to figure out the exact distinction.  That seems
> like a reason to just call it SHA-256 (but in a separate patch).

My assumption has been that when we are referring to the algorithm,
we'll use SHA-1 and SHA-256, and when we're referring to the input to
Git (in config files or in ^{sha256} notation), we use "sha1" and
"sha256".  I see this as analogous to "Git" and "git".

Otherwise, I'm fine with this document as it is.
-- 
brian m. carlson: Houston, Texas, US
OpenPGP: https://keybase.io/bk2204

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  parent reply index

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
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 [this message]
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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