[47324] in Cypherpunks
Re: A weakness in PGP signatures, and a suggested solution (long)
daemon@ATHENA.MIT.EDU (Jiri Baum)
Tue Jan 16 18:37:20 1996
From: Jiri Baum <jirib@sweeney.cs.monash.edu.au>
To: ckey2@eng.ua.edu (Christopher R. Key)
Date: Wed, 17 Jan 1996 10:19:37 +1100 (EST)
Cc: cypherpunks@toad.com
In-Reply-To: <1996Jan11.152134.127675@ua1ix.ua.edu> from "Christopher R. Key" at Jan 11, 96 03:21:34 pm
Reply-To: jirib@cs.monash.edu.au
-----BEGIN PGP SIGNED MESSAGE-----
Hello ckey2@eng.ua.edu (Christopher R. Key)
and cypherpunks@toad.com
> In article <Pine.ULT.3.91.960110182255.18692H-100000@xdm011>, Jeffrey Goldberg <cc047@Cranfield.ac.uk> says:
...
> First of all, if the recipient is a newsgroup, why would that particular
> information need to be part of the signed information? If you post to a
...
Somebody already pointed out an adult message being re-posted to a kidgroup.
...
> Secondly, if you are sending email to some one and sign it using pgp, wouldn't
> that person need pgp to prove that in fact you did sign it? Then it can be
...
> So if all that needs be done to a message to insure that the appropriate
> person reads it is encrypt it using their public key, why does pgp (or one
> of the pgp interfaces) need to be changed to include header information?
...
But then the recipient has a PGP-signed message from you which
isn't encrypted (using pgp -d). That person could then impersonate
you. Eg Alice the jilted lover could resend the goodbye message
with forged headers to Bob's new girlfriend to get back at him.
What a sentence. Here it is again, hopefully understandable:
Bob->Alice
From:Bob; Encrypted(Signed("We're through",Bob),Alice)
Alice does pgp -d, leaving her with Signed("We're through",Bob)
Alice->Carol
From:Bob; Encrypted(Signed("We're through",Bob),Carol)
Later, when Bob gets another girlfriend,
Alice->Danielle
From:Bob; Encrypted(Signed("We're through",Bob),Danielle)
Later still,
Alice->Eve
From:Bob; Encrypted(Signed("We're through",Bob),Eve)
