Re: About git and the use of SHA-1

["Geoffrey Irving" <irving@naml.us>]

On Tue, Apr 29, 2008 at 10:55 AM, Nicolas Pitre <nico@cam.org> wrote:
> On Tue, 29 Apr 2008, Geoffrey Irving wrote:
>
>
> > Sorry for the confusion: it would handwaving if I was saying git was insecure,
>  > but I'm not.  I'm saying that if or when SHA1 becomes vulnerable to collision
>  > attacks, git will be insecure.
>
>  Right.  And if or when that happens then we'll make Git secure again
>  with a different hash.  In the mean time there is low return for the
>  effort involved.

Yes.  I wasn't trying to advocate switching, just making sure people
know that the "collisions don't matter" argument is bogus.

One important thing: when SHA1 becomes vulnerable to collision
attacks, it will still be secure to trust the repositories and tags
that exist *at that moment.*  I.e., the transition period from SHA1 to
the next hash will also be secure, assuming that preimage attacks
don't become possible simultaneously.  So everything is good.

Geoffrey