If you spend much time on Usenet, you've undoubtably run across one or more postings that appear to emanate from users at anon.penet.fi or alpha.c2.org or any of a number of other servers across the Internet which offer anonymous remailing services. And, if you've been following the debate about the so-called "indecency" provisions of the United States' recently-passed telecommunications act, you're undoubtably aware that the authors of the indecency language and their supporters revile anonymous remailers as little more than accessories for the demonic hordes of pedophiles, international terrorists and narco-criminals that infest the Net.
If you actually believe that, I have a bridge I'd like to sell you. The truth is that the typical user of anonymous remailing services posts from an account at work and doesn't want his or her personal political, religious or philosophical opinions to be confused with those of his or her employer.
In 1992, Johan "Julf" Helsingius (firstname.lastname@example.org), president of Penetic, a Helsinki, Finland-based Internet consulting firm, set up what has become to longest-lived anonymous remailing service on the Net. He did so because, as he told Joshua Quittner (email@example.com) in an interview for Wired magazine, "It's important to be able to express certain views without everyone knowing who you are. On things like telephones, people take for granted the fact that they can be anonymous if they want to and they get really upset if people take that away. I think the same thing applies for e-mail."
Julf set up a 386 computer with FreeBSDI and wrote what has come to be known as the Penet semi-anonymous remailer. It works, as do most anonymous remailers, by stripping the original sender's email address off of a received message and replacing it with an anon.penet.fi accountname before forwarding the original content to the destination address. Any messages received in response are similarly anonymized, so that correspondents' true identities are kept hidden from each other. To further muddy the trail, received messages are held for up to 48 hours before being forwarded and are remailed in a different order than they arereceived. The Penet remailer now handles more than 4,000 email messages per day. It's extremely popular. Much too popular, in fact, for the pedophile/terrorist/druglord marketplace to account for more than a tiny fraction of the messages it handles--and anon.penet.fi is only the best-known of nearly two dozen such servers Internet-wide.
The Penet server is called a "semi-anonymous" remailer because, in fact, it maintains an internal database to coordinate real user IDs with their anXXXXX@anon.penet.fi counterparts, so as to properly handle responses. That database has been compromised twice, so far. In February, 1995, based on a warrant obtained by the Church of Scientology, Julf was forced to reveal to Finnish police the true identity of one of the Penet server's users whom the CoS was suing for theft of intellectual property (what has come to be called the "Thetans" breach). Also in 1995, in cooperation with the criminal investigation of an apparent stalking case in the USA, Julf again supplied the name of one of his users to the police.
The first group to tackle the task of creating truly anonymous remailers was the cypherpunks (Internauts with a strong interest in cryptography and nose rings). Since Phil Zimmerman's ubiquitous RSA-based PGP (Pretty Good Privacy) program is a part of every cypherpunk's toolkit, one of the first techniques brought to bear on the problem was the use of embedded email headers encrypted with the remailing server's public PGP key.
In this model, an email message to be forwarded is submitted to a cypherpunk remailer. The remailer strips off the original mail headers and decrypts the PGP-encrypted message body contents. The decrypted message consists of a new set of RFC 822-compliant mail headers and an encrypted body content. The server then resends the message to the address specified in those newly- decrypted headers. The original message often contains three or more encapsulated sets of headers, each of which will be encrypted with the PGP public key of a different remailer. By the time the message has passed through all three forwarding remailers, it is essentially untraceable. The final message content may be in clear text or may be further encrypted with the public key of the recipient. It may contain a set of encrypted, encapsulated headers to permit that recipient to send a reply back through the chain of remailers without ever learning the sender's true identity or the name of any but the first server in the route the response will take.
Considerable effort is involved in crafting messages which can take advantage of these remailers. Joel McNamara's (firstname.lastname@example.org) Private Idaho program for Windows (http://www.eskimo.com/~joelm) makes the task somewhat more transparent. You'll need PGP version 2.6.2 or higher (available in the USA from http://www.gibbon.com/getpgp.html), and you'll also need to finger email@example.com in order to obtain the public keys of the remailers you choose to employ.
Lance Cottrell (firstname.lastname@example.org) created the Mixmaster encrypting, chaining remailer, which is currently available only for Unix OSes. The Mixmaster scheme uses RSA public-key cryptography in conjunction with Digital Encryption Signature (DES) technology and packetization of the original message body to provide better security. It would take me an entire column to describe Mixmaster in detail, but Cottrell does a good job of explaining the technology himself on his home page at http://www.obscura.com/~loki/ (and you can obtain his software there, too).
Raph Levien (email@example.com) maintains detailed information about remailers currently in operation, including response times, reliability and features. The HTML version is available at http://www.cs.berkeley.edu/~raph/remailer-list.html.
For more information about remailers and electronic privacy issues in general, Andre Bacard (firstname.lastname@example.org), author of Computer Privacy Handbook, maintains an Anonymous Remailers FAQ Page at http://www.well.com/user/abacard/remail.html. Arnoud "Galactus" Engelfriet (email@example.com) also maintains an excellent set of links related to privacy, anonymity and cryptography on his home page at http://www.stack.urc.tue.nl/~galactus/remailers/index.html in the Netherlands. You may also want to follow the discussions on the alt.privacy.anon-server Usenet newsgroup.
(Copyright© 1996 by Thom Stark--all rights reserved)