From: Hal <hfinney@shell.portal.com>
Date: Wed, 13 Apr 94 23:21:27 PDT
To: cypherpunks@toad.com
Subject: Re: New anon mailer idea?
Message-ID: <199404140622.XAA20444@jobe.shell.portal.com>
MIME-Version: 1.0
Content-Type: text/plain


Graham Toal's suggestion for automatic insertion of an encrypted
return address block is interesting.  We had some discussion here last
year of a similar approach, although Graham's twist of using a symmetric
rather than PK cypher for the return address is new.  A few thoughts:

 - You'd want this feature to be optional.  Some people might not want
   their anonymity limited by having their return address recorded, even
   in encrypted form.

 - Graham is right about the advantages of use-once (or use-only-a-few-times)
   return addresses.  Chaum discusses how multiple use of return addresses
   allows these systems to be broken, similar to the way Graham describes.

 - The use of a symmetric cypher is a very nice way of getting the use-once
   capability, along with the "burn after reading" effect of a remailer
   chain which destroys itself as it goes.  But it could be a considerable
   burden on the remailer operator to maintain the database.  One possibility
   would be to fix a maximum time limit on how long the return addresses are
   kept "alive" and require some real money to keep them longer.

 - What we would really like is for the recipient to hit the "reply" button
   and be able to send his mail back.  It sounds like this system would still
   require some cut-and-paste.  We already have programs to create encrypted
   remailer chain addresses fairly automatically.  It would be nice to automate
   this last little bit.  Unfortunately, there seems to be no easy way to
   make this work under Graham's scheme.

 - It doesn't look like this would be an easy drop-in to the current remailers,
   unfortunately.  The syntax for how the address would be built up as it
   passes through a chain of remailers is a little unclear as well.

The idea does have a lot of promise, though, and I think it is definately
worth keeping in mind for the next generation of remailers.

Hal