SCHEME for FULL-SPEC RETURN PATH
-----BEGIN PGP SIGNED MESSAGE----- This is a portion of mail that I sent to bill stewart. Since bill seems to busy to send a critique, could someone else comply, please? Jon Boone | PSC Networking | boone@psc.edu | (412) 268-6959 | PGP Key # B75699 PGP Public Key fingerprint = 23 59 EC 91 47 A6 E3 92 9E A8 96 6A D9 27 C9 6C - ------- Forwarded Message Date: Thu, 03 Feb 94 13:45:31 -0500 From: "Jon 'Iain' Boone" <boone@psc.edu> How secure do you think this is? Three remailers: anon1+@a.edu anon2+@b.com anon3+@c.org Originator: boone@psc.edu (really igi.psc.edu, as Message-ID: shows) Receiver: wcs@anchor.ho.att.com ()Ka == contents inside () are encrypted with Public Key of A mail addressed to random+*@foo.edu == mail to user random@foo.edu, random's mail processor will deal with the +* The sender must encrypt his/her own address with the public key of the first remailer and put it in the X-A-R-P: field. Upon reciept of a message with X-A-S-P: set to non-empty, the re-mailer will strip off its portion of the address and decrypt the rest with its private key. It will add itself to the X-A-R-P: and encrypt it in the public key of the next remailer on the X-A-S-P: If there is nothing in the X-A-S-P: (after having removed its own address), then it needs to be sent to the To: address, so we set the From: address to be the contents of the X-A-R-P: with its own address pre- & post- pended. That way, the reciepient need not change his/her mail agent to respond via the X-A-R-P: (or even need to include the X-A-S-P: in the outgoing response). If the message doesn't have an X-A-S-P:, the remailer checks the "To:" for the contents of what would have been the X-A-S-P: with its own address pre- & post- pended. By stripping off its own address and de-crypting the resultant, it has the next address to send it to. Barring wire-tapping, your privacy is susceptible in the logs (syslog, etc.) of the first remailer (a.edu in my example) or if all the RSA-keys for a.edu, b.com and c.org are broken. To dampen wire-tapping, you could encrypt the contents of the message with padding, making traffic analysis more difficult. Comments? IGI.PSC.EDU: To: wcs@anchor.ho.att.com X-A-S-P: anon1+"(anon2+"(anon3+@c.org)Kb"@b.com)Ka"@a.edu X-A-R-P: (boone@psc.edu)Ka From: boone@psc.edu Message-Id: <348723472.AA34890235@igi.psc.edu> A.EDU: To: wcs@anchor.ho.att.com X-A-S-P: anon2+"(anon3+@c.org)Kb"@b.com X-A-R-P: (anon1+"(boone@psc.edu)Ka"@a.edu)Kb From: anon1+@a.edu Message-Id: <2349458.AA23575@a.edu> B.COM: To: wcs@anchor.ho.att.com X-A-S-P: anon3+@c.org X-A-R-P: (anon2+"(anon1+"(boone@psc.edu)Ka"@a.edu)Kb"@b.com)Kc From: anon2+@b.edu Message-Id: <8980234.AA23489203@b.com> C.ORG: To: wcs@anchor.ho.att.com X-A-R-P: anon3+"(anon2+"(anon1+"(boone@psc.edu)Ka"@a.edu)Kb"@b.com)Kc"@c.org From: anon3+"(anon2+"(anon1+"(boone@psc.edu)Ka"@a.edu)Kb"@b.com)Kc"@c.org Message-Id: <2343.AA123@c.org> ANCHOR.HO.ATT.COM: (Reply) To: anon3+"(anon2+"(anon1+"(boone@psc.edu)Ka"@a.edu)Kb"@b.com)Kc"@c.org From: wcs@anchor.ho.att.com Message-Id: <99234.AA23492383@anchor.ho.att.com> C.ORG: To: anon2+"(anon1+"(boone@psc.edu)Ka"@a.edu)Kb"@b.com From: wcs@anchor.ho.att.com Message-Id: <2342349324.AA2343242@c.org> B.COM: To: anon1+"(boone@psc.edu)Ka"@a.edu From: wcs@anchor.ho.att.com Message-Id: <98234234.AA123213@b.com> A.EDU: To: boone@psc.edu From: wcs@anchor.ho.att.com Message-Id: <7732432.AA52342@a.edu> Of course, some work would be necessary to accomodate double-blind conversations. -----BEGIN PGP SIGNATURE----- Version: 2.3a iQCVAgUBLV92F4SAMUrxt1aZAQErUQQAggfMfjxAXS0rk9AL5uZTNN9adGNJqMvF gC5QSlgSki2bmUzfeoq/2cSpdUx7vX9LPCGd88+RnnouyhCDhK0a6fOLGgEDrtar miKGU11Ernt/bQC6gwvBa+KuD7pceLM2mPGw9NLxLMwwajP/U6CxL2/bMXIQhxZ0 eMTM76QuEwE= =tfVg -----END PGP SIGNATURE----- #
From: "Jon 'Iain' Boone" <boone@psc.edu>
How secure do you think this is?
Three remailers:
anon1+@a.edu anon2+@b.com anon3+@c.org
Originator: boone@psc.edu (really igi.psc.edu, as Message-ID: shows) Receiver: wcs@anchor.ho.att.com
()Ka == contents inside () are encrypted with Public Key of A
mail addressed to random+*@foo.edu == mail to user random@foo.edu, random's mail processor will deal with the +* ...
To: anon3+"(anon2+"(anon1+"(boone@psc.edu)Ka"@a.edu)Kb"@b.com)Kc"@c.org From: wcs@anchor.ho.att.com Message-Id: <99234.AA23492383@anchor.ho.att.com>
C.ORG:
To: anon2+"(anon1+"(boone@psc.edu)Ka"@a.edu)Kb"@b.com From: wcs@anchor.ho.att.com Message-Id: <2342349324.AA2343242@c.org> ...
Well, I guess great minds think alike. I'm already working on this. I've been hacking on in my spare time for about a month now. My program is about 75-80% done. Here's how it will work: You send mail to remail+getid@x.edu. The remailer takes your address and encrypts it with its private key, adds some random padding (to disguise the legnth), a checksum, and then puts it in "ascii-armor" format. Then it mails it back to you. You get an address of the format: remail+to+8k3dsa5gzctoy6ahz433mwqqe1v4oo1fr@x.edu Then when you post anonymously, you can use that address as a reply-to address (a few of the cypherpunk remailers allow you to insert your own reply-to fields, i think the BSU ones do.) All of the encryption/decryption routines are completely finished. The only things left to do are to add the actual mail handler that will take an incoming message, decrypt the address and forward the mail. The auto-reply program to send the encrypted addresses is finished also; it works basically like my automatic faq-sender which you can email at mg5n+remailers@andrew.cmu.edu . The above is acutal output from my cipher and will decrypt to mg5n+@andrew.cmu.edu (if you have the secret key!) I chose to use a private key cipher instead of p-k because of the enourmous overhead that you get with PGP, and I was afraid that it would be too big for the mail headers. The cipher used employs transpositions, substitution tables and cipher feedback, in multiple layers of encryption. Perhaps in the future, PGP encryption of the message could be added, and better methods for chaining remailers, and compression of the mail address before encryption (I have experimented with this). I've been a bit busy with other things this past week so I haven't worked on the program lately. If you're serious about this, and you or someone you know is willing to finish the program and actually run a remailer using it, I'll let you have my source code so far. Program is written in C.
participants (2)
-
Jon 'Iain' Boone -
Matthew J Ghio