Adding recipients to an encrypted message?

[mbp2 at Lehigh.EDU]

A suggestion for a new feature...  the ability to add recipients to an encrypted
message.

If I have a file or message that's encrypted to me, and I want to give it
securely to someone else, it's awkward to have to decrypt the whole thing and
then re-encrypt it again to the new person, especially if the file is large. 
It'd be very useful if I could tell GPG to decrypt the session key using my
private key and immediately encrypt it (just the session key) with the new
person's public key, and then add a new recipient packet to the message without
touching the encrypted message body.  This is not only more secure (it's easier
to wipe a small decrypted session key from memory than a whole decrypted
message), but also faster and more convenient.
--

Mike Paul
mbp2 at lehigh.edu
http://www.lehigh.edu/~mbp2/