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99. Appendix III - Cypherpunks (PGP)




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This article is from the PGP FAQ, by Jeff Licquia jalicqui@prairienet.org with numerous contributions by others.

99. Appendix III - Cypherpunks (PGP)

========
What are Cypherpunks?
========

========
What is the cypherpunks mailing list?
========

Eric Hughes <hughes@toad.com> runs the "cypherpunk" mailing list
dedicated to "discussion about technological defenses for privacy in
the digital domain." Frequent topics include voice and data
encryption, anonymous remailers, and the Clipper chip. Send e-mail to
majordomo@toad.com with "subscribe cypherpunks" in the body to be
added or subtracted from the list. The mailing list itself is
cypherpunks@toad.com. You don't need to be a member of the list in
order to send messages to it, thus allowing the use of anonymous
remailers to post your more sensitive messages that you just as soon
would not be credited to you. (Traffic is sometimes up to 30-40
messages per day.)

========
What is the purpose of the Cypherpunk remailers?
========

The purpose of these remailers is to take privacy one level further.
While a third party who is snooping on the net may not be able to read
the encrypted mail that you are sending, he is still able to know who
you are sending mail to. This could possibly give him some useful
information. This is called traffic flow analysis. To counter this
type of attack, you can use a third party whose function is simply to
remail your message with his return address on it instead of yours.

Two types of remailers exist. The first type only accepts plain text
remailing headers. This type would only be used if your goal was only
to prevent the person to whom your are sending mail from learning your
identity. It would do nothing for the problem of net eavesdroppers
from learning to whom you are sending mail.

The second type of remailer accepts encrypted remailing headers. With
this type of remailer, you encrypt your message twice. First, you
encrypt it to the person ultimately receiving the message. You then
add the remailing header and encrypt it again using the key for the
remailer that you are using. When the remailer receives your message,
the system will recognize that the header is encrypted and will use
its secret decryption key to decrypt the message. He can now read the
forwarding information, but because the body of the message is still
encrypted in the key of another party, he is unable to read your mail.
He simply remails the message to the proper destination. At its
ultimate destination, the recipient uses his secret to decrypt this
nested encryption and reads the message.

Since this process of multiple encryptions and remailing headers can
get quite involved, there are several programs available to simplify
the process. FTP to soda.berkeley.edu and examine the directory
/pub/cypherpunks/remailers for the programs that are available.

========
Where are the currently active Cypherpunk remailers?
========

Raph Levien maintains a list of currently active remailers. The list,
unfortunately, seems to change often as remailers are shut down for
whatever reasons; therefore, I am not printing a list here. You can
get the list by fingering remailer-list@kiwi.cs.berkeley.edu.

========
Are there other anonymous remailers besides the cypherpunk remailers?
========

Yes, the most commonly used remailer on the Internet is in Finland. It
is known as anon.penet.fi. The syntax for sending mail through this
remailer is different from the cypherpunk remailers. For example, if
you wanted to send mail to me (gbe@netcom.com) through anon.penet.fi,
you would send the mail to "gbe%netcom.com@anon.penet.fi". Notice that
the "@" sign in my Internet address is changed to a "%". Unlike the
cypherpunk remailers, anon.penet.fi directly supports anonymous return
addresses. Anybody using the remailer is assigned an anonymous id of
the form "an?????" where "?????" is filled in with a number
representing that user. To send mail to someone when you only know
their anonymous address, address your mail to "an?????@anon.penet.fi"
replacing the question marks with the user id you are interested in.
For additional information on anon.penet.fi, send a blank message to
"help@anon.penet.fi". You will receive complete instructions on how to
use the remailer, including how to obtain a pass phrase on the system.

========
What is the remailer command syntax?
========

The first non blank line in the message must start with two colons
(::). The next line must contain the user defined header
"Request-Remailing-To: <destination>". This line must be followed by a
blank line. Finally, your message can occupy the rest of the space. As
an example, if you wanted to send a message to me via a remailer, you
would compose the following message:

      ::
      Request-Remailing-To: gbe@netcom.com

[body of message]

You would then send the above message to the desired remailer. Note
the section labeled "body of message" may be either a plain text
message, or an encrypted and armored PGP message addressed to the
desired recipient. To send the above message with an encrypted header,
use PGP to encrypt the entire message shown above to the desired
remailer. Be sure to take the output in armored text form. In front of
the BEGIN PGP MESSAGE portion of the file, insert two colons (::) as
the first non-blank line of the file. The next line should say
"Encrypted: PGP". Finally the third line should be blank. The message
now looks as follows:

      ::
      Encrypted: PGP
  
      -----BEGIN PGP MESSAGE-----
      Version 2.3a
  
      [body of pgp message]
      -----END PGP MESSAGE-----

You would then send the above message to the desired remailer
just as you did in the case of the non-encrypted header. Note that it
is possible to chain remailers together so that the message passes
through several levels of anonymity before it reaches its ultimate
destination.

========
Where can I learn more about Cypherpunks?
========

ftp://ftp.csua.berkeley.edu/pub/cypherpunks

 

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