New remailer...

13 Oct 1992

      I have been experimenting with Eric's remailing software on
the Sun 4 I use at work.  This is what I've found.

First, Eric's descriptions of how all the different software
components work together have been very helpful.  The software
has gone through three revisions as Eric added new features, so
I implemented them in that order - first the basic remailer,
then adding the "##" and "::" support for header management.

(I had to get perl and slocal before I could get started.
Luckily my system already uses sendmail.)

Basically, I was able to put the parts together the way Eric
described and have it work.  I was able to send messages and
have them remailed.  I even did some tests bouncing mail between
my remailer and Eric's.

Then I tried adding a new feature to the remailer - automatic
message decryption using PGP.  It's not really very secure since
anyone with root privileges at my site can see my pass phrase,
but my site is pretty isolated (a 2400 baud modem is the only link
to the outside world).  For this I had to add one line to Eric's
model .maildelivery file to invoke my PGP filter, and had to write
about a five line shell script to run PGP in a useful way.  I
am still tuning this a little bit but I can send the exact scripts
out when people are ready for them.

One nice thing about this is that, with my remailer plus Eric's,
and with the decryption option, you can now send anonymous messages
for which no one person can tell that you did it.  What you would
do is to send the message first through Eric's remailer, so I
don't know where it came from, then through my remailer, but with
the message encrypted so that Eric can't tell where it's going after
it leaves me.  If more people will run remailers then we'll have
much more security.

I will now tell you how to use it, in case you want to experiment.
But remember that all messages are going across an intermittently-
polled 2400 baud modem, so don't expect fast turnaround and please
don't send a large volume of messages.  Also, please don't pass
information about this remailer beyond this list, for now.

The remailer is at hal@ghs.com.  The basic remailing operation is
as Eric has described: either put "Request-Remailing-To: <dest>" in
the header of the message, or put, as the first two lines of the
body of your message:

::
Request-Remailing-To: <dest>

And follow these two lines with a blank line, then the message to
be forwarded.

Decryption is just a little complicated.  The thing to remember is
that you want to do more than just have me decrypt the message.  You
want me to then remail the message after decryption.  This means
that you should prepare a message with remailing instructions as
above, then encrypt the whole thing, including the "::" and
"Request-Remailing-To:" lines.  Encrypt using PGP with the public
key I show below, and use the -a flag for Ascii output.

This will create a PGP output file, typically with the extension .asc.
The first line will be:

-----BEGIN PGP MESSAGE-----

Now, you can send this message to me, but you have to do one more
thing.  You have to mark it as an encrypted message, by putting the
line "Encrypted: PGP" in the header.  If you can't put stuff into
the headers of messages, then use Eric's "::" feature and add the
following two lines, then a blank line, before "-----BEGIN PGP MESSAGE-----":

::
Encrypted: PGP

Don't forget the blank line after these two.

Now, this message can be sent to my remailer.  It will be decrypted
and then remailed to whomever you requested.

I know this sounds complicated, so let me break it down into steps:

  1. Create the message.

  2. Add "::" and "Request-Remailing-To: <dest>" and a blank line to the
	top.

  3. Encrypt the whole file using PGP and the public key below.

  4. Add "::" and "Encrypted: PGP" and a blank line to the top of
  	the encrypted file.

  5. Send it to hal@ghs.com.

That's not so bad, is it?

Now, if you're really adventurous, here's how to do the double-remailing
process I described above, the one which keeps any one remailer from
knowing who's talking to whom.

  1. Create the message.

  2. Add "::" and "Request-Remailing-To: <dest>" and a blank line to the
	top.

  3. Encrypt the whole file using PGP and the public key below.

  4. Add "::" and "Request-Remailing-To: hal@ghs.com", then a blank line,
  	then "##" then "Encrypted: PGP", then a blank line, to the top of
  	the encrypted file.

  5. Send it to hughes@soda.berkeley.edu

The only complicated step is step 4, where you put in the remailing
request to go from Eric's system to mine, and use the "##" line so
that the outgoing message has "Encrypted: PGP" in the header.

If you want real security, encrypt the message using your friend's
public key after step 1 and send that.  Then nobody will even know
what you're saying, let alone who you're talking to.

As promised, here's the public key for my remailer:

P.S. Coming soon: anonymous return addresses!

Hal

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