Re: Git and SHA-1 security (again)

On Sun, Jul 17, 2016 at 4:21 PM, brian m. carlson
[off-list ref] wrote:

On Sun, Jul 17, 2016 at 10:01:38AM +0200, Johannes Schindelin wrote:

quoted

Out of curiosity: have you considered something like padding the SHA-1s
with, say 0xa1, to the size of the new hash and using that padding to
distinguish between old vs new hash?

I'm going to end up having to do something similar because of the issue
of submodules.  Submodules may still be SHA-1, while the main repo may
be a newer hash.  I was going to zero-pad, however.  I was also, at
least at first, going to force a separate .git dir for those, to avoid
having to try to store two separate types of objects in the same repo.

If it's just the external hash representation, can we go with a prefix
<algo><colon> to identify the hash algorithm? For example
sha256:1234... is SHA-256 while 1235... by default is SHA-1 (but we
could switch the default to SHA-256 via config file later SHA-1 is
dead and nobody wants to type sha256: every time). It catches
incorrect hash algorithm references.
-- 
Duy