Re: [PATCH 0/1] Hashed mailmap support

From: Phillip Wood <phillip.wood123@gmail.com>
To: "Jeff King" <peff@peff.net>,
	"brian m. carlson" <sandals@crustytoothpaste.net>,
	"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Cc: git@vger.kernel.org
Subject: Re: [PATCH 0/1] Hashed mailmap support
Date: Tue, 15 Dec 2020 11:15:06 +0000	[thread overview]
Message-ID: <558dc3da-e0c4-2e7e-83b3-e8f8c431a696@gmail.com> (raw)
In-Reply-To: <X9gV3mKwGrHL7PzV@coredump.intra.peff.net>

Hi Peff, Ævar, Brian

On 15/12/2020 01:48, Jeff King wrote:
> On Sun, Dec 13, 2020 at 01:05:38AM +0000, brian m. carlson wrote:
> 
>> Note that this is not perfect, because a user can simply look up all the
>> hashed values and find out the old values.  However, for projects which
>> wish to adopt the feature, it can be somewhat effective to hash all
>> existing mailmap entries and include some no-op entries from other
>> contributors as well, so as to make this process less convenient.
> 
> I remain unconvinced of the value of any noop entries. Ultimately it's
> easy to invert a one-way hash that comes from a small known set of
> inputs. And that's true whether there are extra noops or not.
> 
> The interesting argument IMHO is that somebody has to _bother_ to invert
> the hash. So it means that the old and new identities do not show up
> next to each other in a file indexed by search engines, etc. That drops
> the low-hanging fruit.
> 
> And from that argument, I think the obvious question becomes: is it
> worth using a real one-way function, as opposed to just obscuring the
> raw bytes (which Ævar went into in more detail). I don't have a strong
> opinion either way (the obvious one in favor is that it's less expensive
> to do so; and something like "git log" will have to either compute a lot
> of these hashes, or cache the hash computations internally).
> 
> I think somebody also mentioned that there's value in the social
> signaling here, and I agree with that. But that is true even for a
> reversible encoding, I think.

 From an obscurity point of view one possible advantage of using a 
one-way function as opposed to just obscuring the raw bytes with a 
reversible encoding is that looking up an old identity requires someone 
to have both the .mailmap and the repository, they cannot get the old 
identities by just downloading the .mailmap file. (I think this the same 
argument as Ævar makes in favor of a reversible encoding as the .mailmap 
file has other uses)

Best Wishes

Phillip

> -Peff
> 