I will avoid re-hashing points that dkg already made.
On Fri, Apr 08, 2016 at 09:07:33PM -0700, Jon Callas wrote:
On Apr 8, 2016, at 8:15 PM, Daniel Kahn Gillmor
<dkg(_at_)fifthhorseman(_dot_)net> wrote:
What is the utility here, specifically?
I appreciate making tracking/linkability harder as a goal, but i'm not
conivnced that this achieves that purpose.
PGP 3 and thus OpenPGP threw the creation time in there as a quickie salt. I
didn't do it. I don't know the full reasons.
I originally thought this was dumb. I got turned around, and believe that
salting the hash is a good thing. I know that I have used this property so
that I can re-use key material, but it's not the total reason.
I can think of a bunch of half-assed things someone can do with key-canonical
fingerprints if they are, say, the NSA. Nothing that's an attack, but just
stuff.
Given that the NSA can easily keep around a database of all public
keys and fingerprints they have observed, I would like to know
what is that hand-wavy “just stuff”.
Moreover, what would be the purpose of reusing the same key material?
If anything, I think that salting the hash ought to be with more than the
timestamp. But really, I'd keep the fingerprint computation the same, just
with a more modern algorithm than SHA-1. The problem we're trying to solve is
that SHA-1 is old. I like to change only one knob at a time.
Which purpose does the “salt” serve here? It doesn't make it harder
to find keys with a similar-looking fingerprint, at least...
Most of all, I think that semantic properties like this shouldn't change
without a reason. At present, there are uses, questionable as they are, for
this, and why break it just because?
Right now, we know that for every fingerprint there is a key (modulo hash
collisions), but a key can have many fingerprints. Why to we want to change
it so that there's one-to-one correspondence between keys and fingerprints?
This sounds to me like it's vaguely surveillance-friendly.
Again, please make this explicit.
Best,
kf
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