computer science

Pseudonymous remailer

Pseudonymous remailer is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Pseudonymous remailer rather than just read about it. In short: A pseudonymous remailer or nym server, as opposed to an anonymous remailer, is an Internet software program designed to allow people to write pseudonymous messages on Usenet newsgroups and send pseudonymous email. Unlike purely anonymous remailers, it assigns its users a user name, and it keeps a database of instructions on how to return messages to the real user.

Key takeaways

Pseudonymous remailer belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Pseudonymous remailer to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Pseudonymous remailer from memory before moving on to harder problems.

Reference excerpt

A pseudonymous remailer or nym server, as opposed to an anonymous remailer, is an Internet software program designed to allow people to write pseudonymous messages on Usenet newsgroups and send pseudonymous email. Unlike purely anonymous remailers, it assigns its users a user name, and it keeps a database of instructions on how to return messages to the real user. These instructions usually involve the anonymous remailer network itself, thus protecting the true identity of the user. Primordial pseudonymous remailers once recorded enough information to trace the identity of the real user, making it possible for someone to obtain the identity of the real user through legal or illegal means. This form of pseudonymous remailer is no longer common. David Chaum wrote an article in 1981 that described many of the features present in modern pseudonymous remailers. The Penet remailer, which lasted from 1993 to 1996, was a popular pseudonymous remailer.

Contemporary nym servers A nym server (short for "pseudonym server") is a 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 PGP keypair and submits it to the nym server, along with instructions (called a reply block) to anonymous remailers (such as Cypherpunk or 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, 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 (based on 2005 figures) in a paper by Bram Cohen, Len Sassaman, and Nick Mathewson.

See also Anonymity Anonymous P2P Anonymous remailer Cypherpunk anonymous remailer (Type I) Mixmaster anonymous remailer (Type II) Mixminion (Type III) I2P-Bote Onion routing Tor (network) Data privacy Penet remailer Traffic analysis

References

Further reading Bruce Schneier (January 25, 1995). Email Security. Wiley. ISBN 0-471-05318-X. Bacard, Andre (1995). Computer Privacy Handbook. Peachpit Press. ISBN 1-56609-171-3.

External links Anonymous Remailer FAQ Mixmaster FAQ Official I2P-Bote eepsite (I2P-internal)

Worked examples

Example 1 — a first encounter with Pseudonymous remailer

Start with the simplest possible case. Write down what Pseudonymous remailer claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Pseudonymous remailer before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Pseudonymous remailer ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Pseudonymous remailer

In research: Pseudonymous remailer appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Pseudonymous remailer in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Pseudonymous remailer is common in secondary-school and first-year university syllabi. It links to neighbouring topics Anonymity networks, Internet Protocol based network software, Network architecture, so understanding it makes those chapters shorter.
In everyday life: Look for Pseudonymous remailer outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Pseudonymous remailer in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Pseudonymous remailer means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Pseudonymous remailer out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Pseudonymous remailer in simple terms?

Why does Pseudonymous remailer matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Pseudonymous remailer?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Pseudonymous remailer.