Messaging Layer Security (MLS) is a security layer for end-to-end encrypting messages. It is maintained by the MLS working group of the

Internet Engineering Task Force The Internet Engineering Task Force (IETF) is a standards organization for the Internet standard, Internet and is responsible for the technical standards that make up the Internet protocol suite (TCP/IP). It has no formal membership roster ...

, 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 In cryptography, forward secrecy (FS), also known as perfect forward secrecy (PFS), is a feature of specific key-agreement protocols that gives assurances that session keys will not be compromised even if long-term secrets used in the session ke ...

, 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 file:Sample cross-section of high tension power (pylon) line.jpg, Overhead power cabling. The conductor consists of seven strands of steel (centre, high tensile strength), surrounded by four outer layers of aluminium (high conductivity). Sample d ...

Mozilla Mozilla is a free software community founded in 1998 by members of Netscape. The Mozilla community uses, develops, publishes and supports Mozilla products, thereby promoting free software and open standards. The community is supported institution ...

and

Cisco Cisco Systems, Inc. (using the trademark Cisco) is an American multinational digital communications technology conglomerate corporation headquartered in San Jose, California. Cisco develops, manufactures, and sells networking hardware, s ...

. 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

Facebook Facebook is a social media and social networking service owned by the American technology conglomerate Meta Platforms, Meta. Created in 2004 by Mark Zuckerberg with four other Harvard College students and roommates, Eduardo Saverin, Andre ...

Google Google LLC (, ) is an American multinational corporation and technology company focusing on online advertising, search engine technology, cloud computing, computer software, quantum computing, e-commerce, consumer electronics, and artificial ...

Twitter Twitter, officially known as X since 2023, is an American microblogging and social networking service. It is one of the world's largest social media platforms and one of the most-visited websites. Users can share short text messages, image ...

University of Oxford The University of Oxford is a collegiate university, collegiate research university in Oxford, England. There is evidence of teaching as early as 1096, making it the oldest university in the English-speaking world and the List of oldest un ...

, and

INRIA The National Institute for Research in Digital Science and Technology (Inria) () is a French national research institution focusing on computer science and applied mathematics. It was created under the name French Institute for Research in Comp ...

. As of March 29, 2023, the IETF has 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 RCS. In March 2025, the

GSMA The GSM Association (GSMA) is a Nonprofit organization, non-profit trade association that represents the interests of mobile network operators worldwide. More than 750 mobile operators are full GSMA members and a further 400 companies in the bro ...

announced the Universal Profile 3.0 standard of RCS would support MLS and

Apple An apple is a round, edible fruit produced by an apple tree (''Malus'' spp.). Fruit trees of the orchard or domestic apple (''Malus domestica''), the most widely grown in the genus, are agriculture, cultivated worldwide. The tree originated ...

announced it would support this RCS standard on Apple Messages.

Matrix Matrix (: matrices or matrixes) or MATRIX may refer to: Science and mathematics * Matrix (mathematics), a rectangular array of numbers, symbols or expressions * Matrix (logic), part of a formula in prenex normal form * Matrix (biology), the m ...

is one of the protocols declaring migration to MLS. Research on adding

post-quantum cryptography Post-quantum cryptography (PQC), sometimes referred to as quantum-proof, quantum-safe, or quantum-resistant, is the development of cryptographic algorithms (usually public-key algorithms) that are currently thought to be secure against a crypt ...

(PQC) to MLS is ongoing, but MLS does not currently support PQC.

Implementations

References

External links

* – The Messaging Layer Security (MLS) Protocol Cryptography Internet privacy Secure communication {{crypto-stub