[messaging] Pond-like tokens for email (was: TOFU to ease PGP key discovery)

[elijah]

On 02/10/2015 10:52 PM, Trevor Perrin wrote:

> By Pond's approach, I think you mean recipients hand out one-time
> delivery tokens to their senders, so their mailbox can accept messages
> or blacklist senders without learning the sender?

Correct me if I am wrong, but afaik we can separate the Pond model into
three parts:

(a) direct delivery from client to recipient server via anonymous mechanism.
(b) the recipient server determines if the message may be received.
(c) using tokens for determining if message should be received.

There is probably some room for experimentation with each aspect,
although it is probably always necessary to block reception at the
server. Nevertheless, I would be willing to block reception at the
client level, which is trivial to do now, and work on the server-side
blocking as the next step. This simple method works until someone
decided to flood an email address, which is, of course, easy to do now
anyway.

> I think one option you're suggesting is an "in-band" exchange of
> tokens (similar to bootstrapping encryption off an in-band exchange of
> public keys).  This wouldn't hide the fact that people communicated
> once, but after an initial email exchange, further communications
> would be opportunistically encrypted and sent over the anonymity
> network.

Yes, I had in mind a system where the anonymity network does not kick in
until after the initial exchange, but nothing specific. But as a first
pass, I would like to just get delivery (a) working and implement (b)
and (c) later.

-elijah