Editing Pseudonymous remailer (section)

==Contemporary nym servers==
A '''nym server''' (short for "[[pseudonymity|pseudonym]] server") is a [[Server (computing)|server]] that provides an untraceable e-mail address, such that neither the nym server operator nor the operators of the remailers involved can discover which nym corresponds to which real identity.

To set up a nym, one creates a [[Pretty Good Privacy|PGP]] keypair and submits it to the nym server, along with instructions (called a ''reply block'') to [[anonymous remailer]]s (such as [[Cypherpunk anonymous remailer|Cypherpunk]] or [[Mixmaster anonymous remailer|Mixmaster]]) on how to send a message to one's real address. The nym server returns a confirmation through this reply block. One then sends a message to the address in the confirmation.

To send a message through the nym server so that the ''From'' address is the nym, one adds a few headers,{{clarify|date=September 2023}} signs the message with one's nym key, encrypts it with the nym server key, and sends the message to the nym server, optionally routing it through some anonymous remailers. When the nym server receives the message it decrypts it and sends it on to the intended recipient, with the ''From'' address indicating one's nym.

When the nym server gets a message addressed ''to'' the nym, it appends it to the nym's reply block and sends it to the first remailer in the chain, which sends it to the next and so on until it reaches your real address. It is considered good practice to include instructions to encrypt it on the way, so that someone (or some organization) doing in/out [[traffic analysis]] on the nym server cannot easily match the message received by you to the one sent by the nym server.

Existing "multi-use reply block" nym servers were shown to be susceptible to passive traffic analysis with one month's worth of incoming [[Spam (electronic)|spam]] (based on 2005 figures) in a paper by [[Bram Cohen]], [[Len Sassaman]], and [[Nick Mathewson]].<ref>See [http://www.cosic.esat.kuleuven.be/publications/article-620.pdf The Pynchon Gate: A Secure Method of Pseudonymous Mail Retrieval] {{cite journal|
  title=The Pynchon Gate: A Secure Method of Pseudonymous Mail Retrieval |
  author=Len Sassaman and Bram Cohen and Nick Mathewson  |
  journal=Proceedings of the Workshop on Privacy in the Electronic Society (WPES 2005)|date=November 2005 |
  editor = Sabrina De Capitani di Vimercati and Roger Dingledine |
  publisher = ACM Press| url=http://www.cosic.esat.kuleuven.be/publications/article-620.pdf |
  accessdate = 2008-06-06
 |doi=10.1145/1102199.1102201
|
 s2cid=356770 }}</ref>