From: Jason Cooper Date: Mon, 02 Oct 2017 19:41:27 GMT Subject: Re: [PATCH v4] technical doc: add a design doc for hash function transition Message-ID: <20171002194127.GI31762@io.lakedaemon.net> In-Reply-To: <20170929173413.GI19555@aiede.mtv.corp.google.com> On Fri, Sep 29, 2017 at 10:34:13AM -0700, Jonathan Nieder wrote: > Junio C Hamano wrote: > > Jonathan Nieder writes: ... > > If it is a goal to eventually be able to lose SHA-1 compatibility > > metadata from the objects, then we might want to remove SHA-1 based > > signature bits (e.g. PGP trailer in signed tag, gpgsig header in the > > commit object) from NewHash contents, and instead have them stored > > in a side "metadata" table, only to be used while converting back. > > I dunno if that is desirable. > > I don't consider that desirable. > > A SHA-1 based signature is still of historical interest even if my > centuries-newer version of Git is not able to verify it. Agreed, even a signature made by a now exposed and revoked key still has validity. Especially in a commit or merge. We know it was made prior to the key being compromised / revoked. This is assuming that the keyholder can definitively say "Don't trust signatures from this key after this date/time+0000". And the signature in question is in the git history prior to that cut off. Tags are a different animal because they can be added at any time and aren't directly incorporated into the history. thx, Jason.