making the X.509 infrastructure available for OpenPGP

Daniel Kahn Gillmor dkg at
Wed Feb 5 06:03:23 CET 2014

On 02/04/2014 12:36 PM, Hauke Laging wrote:
>> I don't know of a formalized way to do the other mapping, but it seems
>> like it would be pretty straightforward to embed the full X.509
>> certificate in a notation packet
> Why wouldn't the fingerprint and the DN not be enough? The whole 
> approach is based on the assumption that the X.509 certificate is 
> already available.

if the X.509 certificate is already available, nothing else needs to be
done.  you can compare the MPIs for the public key directly.

> Using a different key would not make sense.

why not?  many of the main cartel CAs routinely set up special keys for
sub-CAs whose job is to make certain kinds of certifications.  Perhaps
such a sub-CA could be made for issuing OpenPGP certifications?

> That's my opinion, too. And exactly that can be taken over to OpenPGP. 
> Integrated deployment is already there, we just need the technical 
> bridge from X.509 to OpenPGP. And afterwards the OpenPGP certifications 
> by the CAs, of course.

I'd love to see it the other way around, actually (though maybe i'm
misunderstanding you again) -- It would be great to use S/MIME as the
message transport and encapsulation, but use OpenPGP for the certificate
model.  This takes advantage of all the existing message parsing and
packaging in any existing S/MIME client, and reduces OpenPGP support to
a key management and certificate validation plugin.

To do this, i'd likely want to add a pair of S/MIME-specific subkeys to
my OpenPGP certificate (one for encryption, one for signing), so that i
can avoid re-using key material across different cryptographic messaging
schemes (i.e. not use the same signing key for both OpenPGP messages and
S/MIME messages).

Werner recently (in message ID 87zjmv127f.fsf at
indicated his acceptance of a notation named extended-usage at
with a value that can be set to "bitcoin".  Maybe the same notation
could be used to indicate "s/mime-sign" or "s/mime-encrypt" for these
sorts of keys?


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