PGP suggestions (was Re: anonymous mail)

[Derek Atkins <warlord@MIT.EDU>]

> Perhaps it's time we polished the edges, added a few of the features
> that are lacking, and wrote up up an RFC for the PGP message format.

This is being worked on....

> Some features I'd like to see in PGP are:
> 
> 	The ability to send an encrypted message to multiple
> 	recipients without duplicating the entire message.  The
> 	most logical way to do this would probably be to encrypt
> 	the random IDEA key once for each recipient.

This has been in PGP since version 2.2!  Read the docs!  To use this
feature, you just execute:

	pgp -e filename user1 user2 user3...

And it will encrypt the file to all users, using the same IDEA key and
RSA-encrypting it to the different recipients.

> 	There needs to be a facility for having multiple signatures
> 	on a single document without making the signers sign each
> 	others signatures.  Besides the obvious application of
> 	removing a signature from a document, this would also
> 	facilitate things like petitions where many people could
> 	asynchronously sign a single document, and latter assemble
> 	all the signatures together.

This has been discussed.  It is possible to do this in the PGP
protocol, but it has not been implemented.  What this means is that
you could write the code to generate the proper packets to do this,
since those packets are legal, but this code has not yet been written.
It is in the works, but I wouldn't expect to see it in the 2.4
version.

> 	It should be possible (though certainly not mandatory) to
> 	hide the recipient's identity entirely.

This, too, is in the works, albeit a little more difficult to
accomplish.

> 	The message format needs to allow for alternate forms of
> 	encryption (besides IDEA).  Furthermore, the (shared key)
> 	algorithm used to encrypt a message should be hidden in
> 	the RSA encrypted part of the message along with the shared
> 	key.  Ideally, a list of algorithms could be given which
> 	would allow the message to be optionally compressed before
> 	being encrypted, or encrypted two or more times with
> 	different algorithms.

This is already supported.  There is a byte that represents the
secret-key algorithm (and there is a byte that represents the
message-digest algorithm as well).  It would be simple to add, say,
triple-DES to PGP as an alternative encryption algorithm.  As for
hiding the encryption algorithm, this is a possibility but I don't see
it happening.  The data structures, I don't believe, allow for this
currently.  (I'd have to go back and double check this one).

> If I'm confused and the PGP message format already supports some
> of these features, please correct me.

Thats why this message was composed.  Enjoy!

-derek