From: Hal <hfinney@shell.portal.com>
Date: Mon, 6 Feb 95 21:37:24 PST
To: cypherpunks@toad.com
Subject: Re: New directions in anonymity (needed)
Message-ID: <199502070522.VAA27293@jobe.shell.portal.com>
MIME-Version: 1.0
Content-Type: text/plain


From: Noyb, anonymous-remailer@shell.portal.com
>   So, lets look at the
> cost of ataining anonymity.  For U people to communicate M bits (total
> -- 2 people each sending 2 bits is M==4) s/r anonymously takes O(U*M)
> bits multicast bandwidth for Chaum's DC protocol, but the repool
> protocol uses only O(h*M) bits narowcast bandwidth plus O(M) bits
> multicast bandwidth (Where h is the average number of remailer hops,
> expected to be a constant wrt U and M, smaller than U, and much smaller
> than M).

The repool could actually be somewhat worse than this.  Wei has
shown that if you don't send every tick then statistical information
builds up surprisingly quickly to link senders and probable receivers,
especially if there is a pair communicating frequently over a long period
of time, arguably one of the main forms of usage of these nets.  So
everyone has to send all the time at the rate of the maximum per-user
rate accepted by the remailers (say, one packet per tick).  If this rate
is considerably above the actual average communication rate of a given
user then this will be much higher than O(h*M) (although granted it will
not scale directly with U, increasing U will increase the desired packet
rate that would satisfy, say, 90% of users).

Hal