From: Hal <74076.1041@CompuServe.COM>
Date: Fri, 16 Apr 93 09:56:19 PDT
To: <cypherpunks@toad.com>
Subject: ANON: Chaining suggestions
Message-ID: <930416165143_74076.1041_FHD34-1@CompuServe.COM>
MIME-Version: 1.0
Content-Type: text/plain


Will Kinney suggests a form of anonymous return address in which 
"Request-Remailing-To" headers are nested and encrypted, then used for 
addressing.
 
This is a fine idea, Will, but we're way ahead of you on this.  This 
approach has been used ever since we added encryption to the remailers.  
Karl Barrus even wrote a script specifically for constructing anonymous 
addresses like this.  It's available from the Cypherpunks ftp site.  
(soda.berkeley.edu, /pub/cypherpunks.  I think the file is something 
like "scripts.tar".)
 
The problem with this in practice is, first, that the return address 
block is rather large, especially if more than one level of nesting is 
used (often 10, 20 lines or more); and second, that it does not lend 
itself to automatic use of the "reply" function.  Instead, the replier 
has to cut and paste this block of text from the message he's replying 
to and put it in the right place in his own message.  And he has to be 
instructed in how to do this.  (Karl's script adds the instructions when 
it creates the return address.)  This is pretty complicated.
 
This is why Eli suggested (based on suggestions from Eric Hughes) that 
at least Julf's remailer be enhanced so instead of just mapping, say, 
an12345 to joe@foo.com, it would map to a Cypherpunks return address of 
the type Will is describing - a block of encrypted text.  People could 
then have the convenience of automatic replies to an12345 along with the 
security of a chained address.
 
I don't think the idea quite works in this form, since I don't see how 
messages to Julf get translated to an12345.  Presumably only messages 
from one specific user should get posted under this ID (the user whose 
address is buried in the encrypted return address to which Julf's 
remailer will forward replies).  Perhaps another set of commands is 
needed to tell the remailer what ID to use to post under.  By the time 
you do this much I don't think that what you have bears much resemblence 
to Julf's current software.
 
I am stymied in doing experimentation in this area by one fundamental 
problem.  I do not have the power to create user ID's on any systems 
which I use, so I can't create pseudonym accounts.  I have tried various 
tricks.  For example, I sent mail with a "Reply-To:" of 
"hal@alumni.caltech.edu (Pseudonym 12345)".  I hoped that if someone did 
a reply to this mail, it might come to me with that whole field in the 
"To" line, and I could then parse it for the pseudonym number.  That 
didn't work on the particular reply mailer that I used; it stripped the 
comment field in parentheses.
 
The one other idea I've had is to put something at the beginning of the 
Subject: line, so if the user remailed a message with a Subject: of 
"How's it going, Jack?" it would actually go out as "Subject: (P12345) 
How's it going, Jack?".  Then when they reply it will probably come back 
as "Subject: Re: (P12345) How's it going, Jack?" or something similar, 
and I can parse for the (Pxxxxx).  This might work pretty often but 
munging the Subject line is bad for news posting since a lot of news 
readers sort by subject line.  I could put the (Pxxxxx) at the end but 
it might get truncated?  Maybe not.
 
I wonder if anyone knowledgable in mail systems could suggest a 
relatively robust way of setting up outgoing headers so that return mail 
will (A) come back to me (hal@alumni.caltech.edu in this case) and (B) 
be marked in some unique way that would let me do a pseudonym mapping.  
Any ideas would be appreciated.
 
Hal Finney
74076.1041@compuserve.com