Re: Git and SHA-1 security (again)

Hi Zsolt,

On Mon, 18 Jul 2016, Herczeg Zsolt wrote:

quoted

quoted

My point is not to throw out old hashes and break signatures. My point
is to convert the data storage, and use mapping to resolve problems
with those old hashes and signatures.

If you convert the data storage, then the SHA-1s listed in the commit
objects will have to be rewritten, and then the GPG signature will not
match anymore.

Call e.g. `git cat-file commit 44cc742a8ca17b9c279be4cc195a93a6ef7a320e`
to see the anatomy of a gpg-signed commit object.

Yes and no. That's the reason you need the two-way lookup table. If
you need to verify a commit which was signed as SHA-1, you must use
the lookup table in reverse.

That pretends that it is both easy and trustworthy to know when (and how)
to recreate the SHA-1-ified version of the commit object.

Neither is the case, though.

Ciao,
Johannes