"U.S. May Help Chinese Evade Net Censorship"

[Adam Shostack]

On Thu, Aug 30, 2001 at 09:14:46PM -0700, Tim May wrote:
| A mixnet of the N extant remailers offers pretty damned good 
| untraceability. Needs some work on getting remailers more robust, but 
| the underlying nested encryption looks to be a formidable challenge for 
| Shin Bet to crack.

http://anon.efga.org/Remailers lists about 35 Mixmasters and 45 type 1 
remailers.  An awful lot depends on what you mean by "pretty good
untracability."    For example, if you send a dozen messages from
Alice to Bob, then I'd bet you can do an entry-exit correlation
attack.  It becomes harder if you add substantial cover traffic, but
Kocher-esque reductions in the noise are very powerful.

If Alice and Bob are smart spies, and use a different hotmail
recieving address each time, then you get pretty good untracability,
but that untracability comes as much from the one-off nature of the
messages as the mix network between them.  And, depending on how good
I think Shin Bet is at traffic analysis, I'm not sure if I'd even draw
attention to my messages by sending them through 1/40^5 remailers.
Thats 28 or 29 bits with 5 hops.  If you start looking at reliability,
only half or so of the remailers have 99% reliability, although only
10 are below 95% which means either a smaller pool, or a need for
redundancy, both of which reduce your security.

Adam


-- 
"It is seldom that liberty of any kind is lost all at once."
					               -Hume