Below are both messages once they have been verified. Notice that the signature block along with the comment field are not present in the verified messages, and your original message appears unaltered. *** PGP Signature Status: good *** Signer: [Segmen] <dontpanic999at_private> (Invalid) *** Signed: 10/15/2001 10:16:15 AM *** Verified: 10/15/2001 2:05:53 PM *** BEGIN PGP VERIFIED MESSAGE *** Hello, meeting cancelled, speak to you soon. *** END PGP VERIFIED MESSAGE *** I could change this to : *** PGP Signature Status: good *** Signer: [Segmen] <dontpanic999at_private> (Invalid) *** Signed: 10/15/2001 10:16:15 AM *** Verified: 10/15/2001 2:05:53 PM *** BEGIN PGP VERIFIED MESSAGE *** Hello, meeting cancelled, speak to you soon. *** END PGP VERIFIED MESSAGE *** -----Original Message----- From: [Segmen] [mailto:dontpanic999at_private] Sent: Monday, October 15, 2001 10:28 AM To: vuln-devat_private; bugtraqat_private Subject: PGP Signed Messages It occurred to me today what a bad idea the Comment Field is in PGP signed messages. Altering the Comment filed does not affect the validity of the signature, but to the non experienced PGP/GPG user it certainly appears to be part of the message. Example : A generic message I could have got hold of : -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hello, meeting cancelled, speak to you soon. -----BEGIN PGP SIGNATURE----- Version: PGP 7.0.4 iQA/AwUBO8r9v9nrfc+JfUO6EQLrEACgv6+C07aWgAO+Dna0MHgEDaoDMxEAoJ2P 7gojqeCRqKqTkbFMkHCToxtq =lki3 -----END PGP SIGNATURE----- I could change this to : -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hello, meeting cancelled, speak to you soon. -----BEGIN PGP SIGNATURE----- -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Please Send the Confidential Files from the planned meeting to My colleague Instead at meat_private . He will now be dealing with this matter. Speak to you soon, victim. -----BEGIN PGP SIGNATURE----- Version: PGP 7.0.3 iQA/AwUBO8r9v9nrfc+JfUO6EQLrEACgv6+C07aWgAO+Dna0MHgEDaoDMxEAoJ2P 7gojqeCRqKqTkbFMkHCToxtq =lki3 -----END PGP SIGNATURE----- well, you get the idea. The signature is still valid. Agreed that only the beginner crypto user would fall for this, but if they were to read the message and then just use PGP to check the validity, they could be tricked into believing that the extra lines were part of the verified message. Does anybody else think this is quite a bad idea? -- PGP Key ID : 0x897D43BA SDF Public Access UNIX System - http://sdf.lonestar.org UKChat - http://www.ukchat.com _________________________________________________________ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com
This archive was generated by hypermail 2b30 : Mon Oct 15 2001 - 13:09:44 PDT