From: Rick Busdiecker <rfb@lehman.com>
Date: Mon, 8 Aug 94 08:40:54 PDT
To: Hal <hfinney@shell.portal.com>
Subject: Re: Remailer ideas
In-Reply-To: <199408060511.WAA24892@jobe.shell.portal.com>
Message-ID: <9408081539.AA25778@fnord.lehman.com>
MIME-Version: 1.0
Content-Type: text/plain


    Date: Fri, 5 Aug 1994 22:11:59 -0700
    From: Hal <hfinney@shell.portal.com>
    To: cypherpunks@toad.com
    Subject: Re: Remailer ideas
    References: <9408051709.AA14763@ah.com>
    
    . . .

    A copy of outgoing email could be kept, acknowledgements received
    on receipt, and the email deleted or re-transmitted as needed.  Serial
    numbers would distinguish retransmissions so that redundant resendings
    (where the packets "crossed in the mail", so to speak) would be dropped.
    All this was designed in an afternoon in Xmodem.  It's conceptually easy.
    The hard part is getting a standard and getting people to build it into
    their Mail User Agents.

I think that many of the simple cases are conceptually easy, but even
slightly complicated ones are non-trivial.  For example, I tend to
include Return-Receipt-To: lines in my messages, so I get a bunch of
responses.  Interpreting those responses and deciding what action
would be appropriate raises some interesting questions, not the least
of which is ``What does it mean for a message to be successfully
delivered to the cypherpunks list?''.  Just as an example how easily
the issue can become confused, I'll throw in, ``How is the meaning of
successful delivery affected by changes in list membership during
transmission?''  Considering that some of the addresses to which
cypherpunks is distributed are also distribution lists, any list
related problems are multiplied.

Practical issues make this whole thing more difficult.  The ``getting
people to build it into their Mail User Agents'' part in particular.
The idea of a Return-Receipt-To: field has been around for a while,
but the semantics have never been pinned down.  Some mailer daemons
generate replies meaning that the bits were delivered.  Some readers
(MUAs?) generate replies based on end-user actions.

This thread of discussion got me thinking about a really sick thought
though:  Using email messages to represent UDP packets.

			Rick