computer science

Messaging Layer Security

Messaging Layer Security 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 Messaging Layer Security rather than just read about it. In short: Messaging Layer Security (MLS) is a security layer for end-to-end encrypted messages. It is maintained by the MLS working group of the Internet Engineering Task Force (IETF), and is designed to provide an efficient and practical security mechanism for groups as large as 50,000 and for those who access chat systems from multiple devices.

Key takeaways

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

Reference excerpt

Messaging Layer Security (MLS) is a security layer for end-to-end encrypted messages. It is maintained by the MLS working group of the Internet Engineering Task Force (IETF), and is designed to provide an efficient and practical security mechanism for groups as large as 50,000 and for those who access chat systems from multiple devices.

Security properties Security properties of MLS include message confidentiality, message integrity and authentication, membership authentication, asynchronicity, forward secrecy, post-compromise security, and scalability.

History The idea was born in 2016 and first discussed in an unofficial meeting during IETF 96 in Berlin with attendees from Wire, Mozilla and Cisco. Initial ideas were based on pairwise encryption for secure 1:1 and group communication. In 2017, an academic paper introducing Asynchronous Ratcheting Trees was published by the University of Oxford and Facebook setting the focus on more efficient encryption schemes. The first BoF took place in February 2018 at IETF 101 in London. The founding members are Mozilla, Facebook, Wire, Google, Twitter, University of Oxford, and INRIA. On March 29, 2023, the IETF approved publication of Messaging Layer Security (MLS) as a new standard. It was officially published on July 19, 2023. At that time, Google announced it intended to add MLS to the end to end encryption used by Google Messages over Rich Communication Services (RCS). In March 2025, the GSMA announced the Universal Profile 3.0 standard of RCS would support MLS and Apple announced it would support this RCS standard on Apple Messages. Both Google Messages and Apple Messages began the rollout of MLS E2EE over RCS in May 2026. Matrix is one of the protocols declaring migration to MLS. In 2026, Discord rolled out end-to-end encryption on voice and video calls, using MLS for scalable group key exchanges. Research on adding post-quantum cryptography (PQC) to MLS is ongoing. The IETF has prepared an Internet-Draft using PQC algorithms in MLS.

Implementations

References

External links RFC 9420 – The Messaging Layer Security (MLS) Protocol

Worked examples

Example 1 — a first encounter with Messaging Layer Security

Start with the simplest possible case. Write down what Messaging Layer Security 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 Messaging Layer Security 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 Messaging Layer Security 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 Messaging Layer Security

In research: Messaging Layer Security 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 Messaging Layer Security 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: Messaging Layer Security is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cryptography, Internet privacy, Secure communication, so understanding it makes those chapters shorter.
In everyday life: Look for Messaging Layer Security 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 Messaging Layer Security in 20 minutes

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

Frequently asked questions

What is Messaging Layer Security in simple terms?

Why does Messaging Layer Security 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 Messaging Layer Security?

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 Messaging Layer Security.