There seems to me to be a serious problem with the "novel return address" idea. The information that ties together multiple anonymous messages from the same person is out in the world, encrypted by a single key in a conventional cipher. If that single key is compromised, everyone's identity is exposed. (Or, at least, the correlation among all messages sent by that individual, even if their legal or email name is not revealed). Furthermore, breaking the key will be possible by sending test-probes and doing exhaustive search. E.g. if you add 128 bits of salt, someone can send five or ten messages to themself through the remailer, and accumulate ten encrypted addresses that are known to be for the same sender. When decrypted, these keys will have maybe a 16- or 32-bit "return address ID" and 128 bits of salt. The attacker can then search the key space for keys that include large numbers of identical bits when decrypting those ten keys. This search is easily amenable to parallelization, fast hardware also exists to do it, and it may be possible to find improved algorithms to use the knowledge of identical plaintext bits to speed up the search process. The idea also suffers from the dossier problem -- all the information about return addresses will exist in a single place (at the remailer site) where it's tempting for a government (or other adversary of privacy) to try for it. Keep thinking, folks! We aren't there yet... John