What happens when a key expires?

[Johan Wevers]

Jean-David Beyer wrote:

> I expect that a little before 2002-09-22 comes around, I will make a new
> 1024g key to replace EEF02424 and export it to some keyservers. But what
> happens to the e-mails I have received (assuming I have kept them) that
> have been encoded with EEF02424?

You are still able to decrypt them. An expiry date is only a way to tell
an implementation not to use a key any more after a certain date, but
there is no cryptographical method to enforce that (and it would be
easily circumvented by setting back the time on your machine).

> I would not want people sending me new email with EEF02424 after that key
> expires, and I suppose they will not.

But they still could. I still receive email encrypted with a compromised
key which I revoked, for which I sent the revocation certificate to the
keyservers and with warnings on my site not to use it any more. :-(

> But will I still be able to read the old e-mails (provided I do not
> delete it from my private keyring)?

Yes. BTW, that's also possible with revoked keys.

-- 
ir. J.C.A. Wevers         //  Physics and science fiction site:
johanw@vulcan.xs4all.nl   //  http://www.xs4all.nl/~johanw/index.html
PGP/GPG public keys at http://www.xs4all.nl/~johanw/pgpkeys.html