ietf-openpgp
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Re: Interop grill-off

2005-09-20 09:17:49

On Tue, Sep 20, 2005 at 11:17:05AM -0400, David Shaw wrote:

3. Some keyservers do not return matching keys, if searched by the long
(16 byte) key ID of a subkey. SKS is guilty of this.

Isn't this a just SKS feature request?  Nothing in the draft says
anything about how keyservers work, or even that a UI must allow
particular ways to search.

No, it isn't. This becomes a major interoperability issue, when you use
signature subkeys. It's not quite clear from RFC2440 wether the 8-byte
signatory field sould point to the main key or the subkey, but in several
implementations it points to the subkey, which actually made the signature
(and this is the right behavior, IMHO).

In this case, databases of keys, be it local keyrings or remote keyservers
MUST be indexed by subkey IDs as well, otherwise such signatures cannot be
verified. For example, this SKS deficienci breaks interoperability (namely
yautotmatic key retrieval) with GnuPG (and very possibly PGP), if signature
subkeys are used.

Signature subkeys have many uses, and although they are less popular than
encryption subkeys (because of the default settings of pgp and gpg) their
use is an important security measure allowing for changing the regularly
used signing key without losing all certificatitons on the main key. They
are also useful if the same user wishes to make signatures from different
computers without risking too much.

-- 
Daniel

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