To send truly anonymous email, one must use a Mixmaster system. Later on, we'll see how Freedom.net draws upon the ideas of the Mixmaster system to create a powerful general system for Internet communication. A fair number (more than a dozen) nodes operate publicly-accessible Mixmaster systems. A client wishing to send an anonymous message retrieves each of their public keys. (see sidebar on Public Key Cryptography for more information on how public/private keys work.) The client picks three of the machines: A, B, and C, to send her message. The client then encrypts the message and the destination with C's public key. C's address is then tacked onto the encrypted bundle, and the lot is then encrypted with B's public key. Finally, that encrypted bundle has B's address tacked on and is finally encrypted with A's public key. The whole bunch is sent to A. A then decrypts the message, revealing B's address and a bundle of unreadable data. A sends the bundle to B. B then decrypts the data to reveal C's address and another bundle of data. B forwards the message to C, C decrypts the last chunk of the bundle and discovers the final message and its recipient and sends the message, unencrypted, to its final destination.Unless the recipient can discover all three machines that were used, ensure that all three machines kept logs of all transactions, and coerce all three entities to cooperate in revealing their private keys, the original sender cannot be discovered. If only one of A, B, or C, refuses to comply, the sender cannot be discovered. If these systems are processing a great deal of email and wait a random amount of time before decrypting and forwarding on a message, it becomes effectively impossible for someone monitoring the network to correlate an incoming with an outgoing message. If all three systems are in different, and liberal, countries, the legal complications become effectively insurmountable. As of the writing of this essay in mid-June 2000, there has not been even an attempted legal attack on the decade-old Mixmaster system.