Creating signatures with expiration time

[Jesus Cea]

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Hi, everybody.

I have a corporate PGP key we use to sign employee keys to validate the
UID belonging to the corporation (that is, that the email present in the
key is actually assigned by us).

My idea was to create a signature with a expiration date, so signatures
should be renewed every year. The OpenPGP Standard documents this type
of signature <http://tools.ietf.org/html/rfc4880#section-5.2.3.10>, but
GPG doesn't seems to have the option to create them.

That is, when I create a signature, I have no way to introduce an
expiration date.

Am I missing anything?. I am using GPG 1.4.10. I would consider moving
to GPG 2 if necessary.

PS: We could manage with revocation signatures, but people would need to
refresh the keys. With a expired signatures people would need to refresh
to see the extension, so they would do.

- -- 
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