Re: [Gnu-arch-users] crypto features and 1.2preX

[Florian Weimer]

Brian May wrote:

> 1. I have heard, from other mailing lists, that it is feasible to
> alter a file *and* *its* length* in such a way that it will produce
> exactly the same MD5 Checksum. The moral of the story was you can't
> rely on the MD5 checksum by itself, you need the MD5Sum + Length of
> the data.

As far as I know, this problem is specific to the old version 3 public
key format of OpenPGP.  In this case, two values are concatenated, and a
single hash is computed over that concatenation, so it's possible to
alter the boundary between the two values.

> Here, the signature is made with my key, but tla doesn't realize that
> the creator field was forged.

This has to be handled in the signature verification script.  You
probably want to use a separate keyring and disable the web-of-trust
mechanism (after checking key validity manually).