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From: "H. Peter Anvin" <hpa@zytor.com>
To: "git@vger.kernel.org" <git@vger.kernel.org>
Subject: Migrating away from SHA-1?
Date: Tue, 12 Apr 2016 15:38:04 -0700	[thread overview]
Message-ID: <570D78CC.9030807@zytor.com> (raw)

OK, I'm going to open this can of worms...

At what point do we migrate from SHA-1?  At this point the 
cryptoanalysis of SHA-1 is most likely a matter of time.

For existing repositories we will need to have a migration mechanism. 
Since we can't modify objects without completely invalidating the 
cryptographic properties, what I would suggest is that we leave the 
existing objects as is, with a persistent lookup table from SHA-1 to 
<new hash>, and have that lookup table signed (e.g. GPG) by the person 
responsible for converting the repository.  This freezes the 
cryptographic status of the existing SHA-1 objects at the time the 
conversion happens.  This is a very good reason to do this before SHA-1 
is actually broken  In contrast. SHA-2 has been surprisingly resistant 
to cryptoanalysis, to the point that SHA-3 was motivated by performance 
and the desire to have a well-tested function based on entirely 
different principles should a generic attack against the common 
structure of MD5/SHA-1/SHA-2 would ever be found.

	-hpa

             reply	other threads:[~2016-04-12 22:38 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-04-12 22:38 H. Peter Anvin [this message]
2016-04-12 23:00 ` Migrating away from SHA-1? Stefan Beller
2016-04-12 23:06   ` H. Peter Anvin
2016-04-12 23:15   ` Jeff King
2016-04-12 23:15   ` David Turner
2016-04-12 23:44     ` Jeff King
2016-04-14  1:53     ` Theodore Ts'o
2016-04-14 16:47       ` Joey Hess
2016-04-14 17:23       ` David Turner
2016-04-14 17:28         ` H. Peter Anvin
2016-04-14 22:40           ` Theodore Ts'o
2016-04-15  2:13             ` Jeff King
2016-04-15  2:18               ` Junio C Hamano
2016-04-15  2:22                 ` Jeff King
2016-04-12 23:42 ` Jeff King
2016-04-13  1:03   ` Junio C Hamano
2016-04-13  1:36     ` Jeff King
2016-04-13  1:38     ` H. Peter Anvin
2016-04-13  1:51 ` Duy Nguyen
2016-04-13  1:58   ` H. Peter Anvin
2016-04-15  1:50     ` brian m. carlson
  -- strict thread matches above, loose matches on Subject: below --
2016-06-18  2:10 Leo Gaspard
2016-06-18  3:30 ` Eric Wong
2016-06-24 18:17 ` brian m. carlson

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