Re: O.J. ObCrypto: Fuhrman's Folly Fans Fakery Fears...

>I do not think that PGP 2.x can easily (ie: Automatically) use one key for
>Signing and another for Encrypting a Message (it does both at the same time
>if you ask). If I "Clear Sign" a message and then Encrypt it, then I get
>the result but I'm not sure if doing the decrypt on such a message will
>automatically spot the signature and verify it (as would occur with a E+S
>pass).

PGP identifies the key for decryption and signature checking from the message.
When you're signing a message or key, you can pick which of your keys to
use with the -u option.  The difficulty is getting people to use your
encryption key instead of your signature key when encrypting stuff for you.
Derek mentioned one approach (get people to load the encryption key first);
unfortunately, you can't predict their behavior, and if you change encryption
keys more often than signature keys, they'll load the newest encryption key
last.
Another approach is to identify them in the names - my key certification key
says "KeyCert-only" in the text.

For the problem that started this discussion, though, there's no good solution.
Since the Bad Guys _can_ encrypt a message to you with your signature key,
and send it to you by anonymous remailer, they can plant a reason to suspect
that you may have evidence encrypted with that key.
#---
#                                Thanks;  Bill
# Bill Stewart, Freelance Information Architect, stewarts@ix.netcom.com
# Phone +1-510-247-0664 Pager/Voicemail 1-408-787-1281
#---

> unfortunately, you can't predict their behavior, and if you change
> encryption keys more often than signature keys, they'll load the
> newest encryption key last.

Actually, the most recently-added key will be the one that is
used.. So updating your encryption key works fine, since the most
recent encryption key will be on top, and hense used first.

> For the problem that started this discussion, though, there's no good
> solution.  Since the Bad Guys _can_ encrypt a message to you with your
> signature key, and send it to you by anonymous remailer, they can
> plant a reason to suspect that you may have evidence encrypted with
> that key.

True.. To get around this problem you need the concept of a two-key
certificate... However a rogue user could still use the signature
key to encrypt, so I'm not sure that even this would help the problem.

-derek