computer science

Xx messenger

Xx messenger 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 Xx messenger rather than just read about it. In short: xx messenger is a cross-platform decentralized encrypted instant messaging service developed by David Chaum and partners and running on a blockchain called xx network. Messages are delivered over a variety of mix network first described in 2016.

Key takeaways

Xx messenger 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 Xx messenger to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Xx messenger from memory before moving on to harder problems.

Reference excerpt

xx messenger is a cross-platform decentralized encrypted instant messaging service developed by David Chaum and partners and running on a blockchain called xx network. Messages are delivered over a variety of mix network first described in 2016. Users can send one-to-one and group messages, which can include voice notes and images. xx messenger uses usernames as identifiers which can be optionally attached to standard cellular telephone numbers or email addresses for contact discovery. All communications between users are secured with quantum-resistant end-to-end encryption. xx messenger's software is free and open-source. Its mobile clients are published under the 2-clause BSD License, while its server software is published under a modified, patent-protected Business Source License.

History An alpha version of xx messenger was first presented on January 6, 2016 by David Chaum at the Real World Crypto conference with the stated goal of demonstrating a new type of mix network encryption scheme. The encryption scheme, known as PrivaTegrity, was described by Chaum and team of academic partners at Purdue University, Radboud University Nijmegen, University of Birmingham, and other schools. xx messenger was released to the public as a mobile app on Android and IOS on 25 January 2022.

Architecture

cMix xx messenger uses cMix - a network of decentralized servers called xx network that are run by independent operators in approximately 80 countries - for data transmission. cMix attempts to address traditional latency and scalability limitations of mix networks by performing computationally expensive public-key operations between mix nodes prior to any client data being transmitted over the network. Messages sent by users of xx messenger are grouped in batches of 1,000 and routed through a subset of cMix nodes. Once the mixing process is complete, each message can be retrieved and decrypted by their recipient.

Encryption protocols The cMix protocol uses XChaCha20, BLAKE2b, HMAC-SHA-256, Diffie–Hellman key exchange, and Supersingular isogeny key exchange as cryptographic primitives. Messages are encrypted in two layers. The inner layer is encrypted with ChaCha20 symmetric encryption. This payload is then encrypted once more for transmission over the mixnet using multi-party ElGamal encryption. The encryption protocols, in addition to the properties provided by the mixnet, allow both anonymity preservation and traditional end-to-end security guarantees, as well as preliminary post-quantum security with a traditional fallback mechanism.

Worked examples

Example 1 — a first encounter with Xx messenger

Start with the simplest possible case. Write down what Xx messenger 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 Xx messenger 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 Xx messenger 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 Xx messenger

In research: Xx messenger 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 Xx messenger 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: Xx messenger is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cross-platform software, Cryptographic software, Free VoIP software, so understanding it makes those chapters shorter.
In everyday life: Look for Xx messenger 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 Xx messenger in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Xx messenger 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 Xx messenger out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Xx messenger in simple terms?

Why does Xx messenger 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 Xx messenger?

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 Xx messenger.