nelson@crynwr.com writes:
Scott Brickner writes:
The "to" and "from" values that the traffic analyst will be using are the IP addresses in the packets. It doesn't matter whether mixmaster, cypherpunks, or penet remailers are used, they still use IP addresses.
Sure *does* matter. There's no computationally feasible way to associate one mixmaster message with another. The only way you can get a clue is by analyzing who sends mail into and out of the mixmaster system. If both of your endpoints are within the mixmaster system, you have no entering or exiting mail to analyze. It doesn't matter if the mixmaster remailers are on the same or different systems.
Scott indicates, in private mail, that he needs another, clearer, explanation. Okay, here goes: A is sender, B is recipient, M is mixmaster remailer network, W is watcher. A Mixmaster system (there can be more than one, although there is currently only one published Mixmaster system of remailers) acts as a single node for the purposes of traffic analysis. Imagine, if you will, a remailer that everyone trusts implicitly. Why would you need any other remailers?? All W can see is incoming mixmaster messages (lets you identify A), and outgoing ASCII messages (lets you identify B). If W can correlate traffic between A and B, he does it by watching what happens between A and B, not being privy to the internals of M. Now obviously there is no single trustable M. So, you create many Ms, who move traffic between themselves. Let's assume that only one of them is trustable (M') and happens to be used by A to send a message to B. W STILL doesn't know what happens inside M' and has no more information about the correlation between the message sent by A and the message received by B than in the first case. Do you see now, Scott? Adding mixmasters doesn't need to make traffic analysis harder (it does, but it doesn't need to). It makes finding an M that you trust easier. And to that end, it doesn't matter if those mixmasters are all running on the same host or not. Now, my point about increased security by sender and/or receiver running a Mixmaster remailer is that W has an easy time identifying A and B because he can see that A sends a mixmaster message, and B receives an ASCII message from a mixmaster remailer. If either A or B is running a mixmaster, W is denied knowledge that A or B even exists. He MUST assume that anyone running a remailer is receiving or sending some or all of the messages. Message counting (looking for a delta implying an internally received or transmitted message) is no help. Since mixmaster happily ignores bogus messages, I could receive a message, fill its packets with junk, send them one or more hops, and let someone *else* be under suspicion of having received a message. As an aside, the TLAs *are* looking for A's and B's. They spend millions of dollars a year on telephone traffic analysis. We MUST assume that they would spend tens of thousands of dollars a year on email traffic analysis. -russ <nelson@crynwr.com> http://www.crynwr.com/~nelson Crynwr Software | Crynwr Software sells packet driver support | PGP ok 11 Grant St. | +1 315 268 1925 voice | It's no mistake to err on Potsdam, NY 13676 | +1 315 268 9201 FAX | the side of freedom.