From: Hal <hfinney@shell.portal.com>
Date: Thu, 12 May 94 23:26:17 PDT
To: cypherpunks@toad.com
Subject: Re: Message Havens, gopherholes
Message-ID: <199405130627.XAA10537@jobe.shell.portal.com>
MIME-Version: 1.0
Content-Type: text/plain


One problem I see with Karl's suggestion (if I understand it) is that
there needs to be some pre-arrangement between sender and receiver in
order for the receiver to know what "tag" will be used to identify the
next message.  That way he knows to download it after scanning all the
tags (plus, he downloads a certain number of other messages as cover).
(In other words, every day he downloads five messages from the message
haven.  He does this whether he has anything there or not.  An eaves-
dropper doesn't know how many of the five are for him and how many are
just random.)

I think it should be possible to have a way of marking a messages as being
for a particular user without any pre-arragement, and without any outsider
being able to determine which messages are for which user.  Simply encrypting
some standard constant number with the user's public key would be close to
right, although you'd have to find a way to keep the modulus size from
leaking out.

The main down side to this is that the decryption and tag check might take
too long, while Karl's pre-arranged tag idea could be very fast.  Perhaps
both concepts would be useful in different contexts.

Hal