From: "Robert J. Woodhead" <trebor@foretune.co.jp>
Date: Tue, 26 Oct 93 02:34:51 PDT
To: Eli Brandt <ebrandt@jarthur.Claremont.EDU>
Subject: Re: Totally Anonymous Remailing
In-Reply-To: <9310260243.AA27775@toad.com>
Message-ID: <9310260929.AA13959@dink.foretune.co.jp>
MIME-Version: 1.0
Content-Type: text/plain


Eli writes regarding my Totally Anonymous Mailing scheme:
>A problem here.  The SEND system eliminates the risk of database
>seizure, and encrypting mail to the remailer eliminates snooping on
>incoming mail, but outgoing mail is unprotected.  Anybody watching
>net traffic coming out of the TAR can snoop the destination of SEND
>requests, and reasonably presume that address to be the owner of the
>nym.  This is of course a problem with a penet-style setup too, but
>it's something to fix if you want to be "totally anonymous".  

I don't think this is a problem.  The send command is received by
the mailing system encrypted by the mailer's public key.  An outside
observer can't decode the message.  When it gets the message, the
mailer decrypts the envelope, and gets the sender's pseudonym and
an encrypted command (encrypted with the sender's private key).
The mailer knows the pseudo's public key, so it can decrypt the
command.  If it is a spoofed command, the mailer gets junk, and
merely sends email into the psuedo's account giving details of
the intrusion attempt (which might just be an error on the
owner's part).

The outgoing mail packet(s) would be encrypted by the pseudo owner's
public key, so only he could read them.

Some mechanism might have to be added to prevent an irritating "spoof"
attack where the attacker records an incoming message and merely
duplicates it.  This might involve having the server remember the last
couple of weeks of command transactions, reject duplicates, and
reject any messages more than a week "old."  This would require a
timestamp in the encrypted part of the message.

The part of the proposal that really needs work is methods to make
traffic analysis prohibitive.  I suspect that a net of cooperative
mailers, along with the ability to delay the relay of outgoing mail,
might help in that regard.