REMAIL: X-TTL and X-Discard

[nobody at eli-remailer]

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I don't see that X-TTL is very useful as currently proposed.  As I see
it, I would have to create something like this:

=======================================
::
X-TTL: 5
Request-Remailing-To: remailer1

::
Request-Remailing-To: remailer2

::
Request-Remailing-To: remailer3

::
Request-Remailing-To: remailer4

::
Request-Remailing-To: remailer5

Dummy message to be sent.
=======================================

(Or an equivalent structure could be set up with nested PGP encryptions.)

This would go through remailers 1, 2, 3, 4, and 5, decrementing the
X-TTL field each time, and after the last one when it was 0 the message
would be deleted.  The X-TTL is not very convenient in this case since
you still have to come up with a path for sending your message which is
at least as long as the X-TTL value.

It seems to me that the X-Discard idea is simpler; you can just put the
X-Discard in the command block for the last remailer, and you don't have
to count them.

What is needed to make X-TTL useful is for the remailer to choose another
remailer as its destination, and ideally to encrypt the message before
sending it.  This way X-TTL can be used to insert a random remailer path of
n hops in the middle of a sender-constructed remailing path.  This leads to
a system where the remailer decrypts an incoming message, reads the X-TTL
value, decrements it, re-encrypts the message for the next remailer in the
chain, and sends it.  The X-TTL value is never exposed to outsiders.

At one point I wrote a modification to my remailer to cause it to
encrypt any message which it sent to another remailer which supported
PGP.  But I decided that this didn't really help security enough to
be worthwhile.  It would be much better to encourage users to encrypt
their messages themselves in a nested fashion so that no remailer sees
any more information than the bare minimum necessary.

Hal Finney
74076.1041 at compuserve.com

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