From: b44729@achilles.ctd.anl.gov (Samuel Pigg)
Date: Wed, 25 Aug 93 06:35:37 PDT
To: cypherpunks@toad.com
Subject: Attacks on remailers
In-Reply-To: <9308251148.AA25085@tamsun.tamu.edu>
Message-ID: <9308251334.AA22042@achilles.ctd.anl.gov>
MIME-Version: 1.0
Content-Type: text/plain



   > Response: Encrypt the messages.  Use "nesting", so that all that is
   > visible as each message leaves a remailer is the destination of the
   > next remailer.

   This should be made smoother.  The learning curve needed to
   get to this stage : install PGP & get it working, learn
   how to use remailers, install remailer nesting script, debug
   all of the above, because something in there is bound to
   break at this stage : quite a lot of work!  Just
   improving things up to here with clearer documentation,
   and better scripts and GUIs, would greatly increase the number
   of remailer users and traffic.

Working on it. (NeXT version at least.)

	[..]

   Here's another item: faster links!  The delay between
   when I post this and when it arrives on "cypherpunks" can
   be half a day. 

   What about that idea of using direct sockets instead of
   SMTP between remailers?  That could kill two birds with one stone:
   delivery speed and cheap attacks against the intermediate
   links via logging or spool files.



Actually what I was proposing was the direct usage of SMTP itself rather
than going through the host machine's mail system. As anyone can do it,
it would help with the usage of student accounts as remailers.
And with direct SMTP (socket connections to port 25 of the receiving machine)
you have some control over the header information that is generated.

The protocol is outlined in RFC821 if anyone wants to look at it.

So that's 4 birds with one stone:

	(1) Speed.

	(2) No logging on remailer host.

	(3) Control over header information (hell you could even make 
	    something up for the header fields that looks 'legitimate')

	(4) Tighter control of possible batching by not going though
	    the host machine's mail system.

Earlier it was noted that traffic analysis worked for the a.s.a.r. remailer
to find the sender of messages by checking the logs on the machine
that the messages were originally from. With a simple utility someone could
submit mail directly to the remailer host using sockets, and so leave little
trace on their host of having done so.

I'm working on the tiny utility to send mail via socket 25
(I'm sure it has been done many times before, and is probably already
available somewhere. Is no big deal.)

School is of course stealing my time.
-Sam
(is the remailer source code available on soda?)