Crate mls_rs

An implementation of the IETF Messaging Layer Security end-to-end encryption (E2EE) protocol.

What is MLS?

MLS is a new IETF end-to-end encryption standard that is designed to provide transport agnostic, asynchronous, and highly performant communication between a group of clients.

MLS Protocol Features

• Multi-party E2EE group evolution via a propose-then-commit mechanism.
• Asynchronous by design with pre-computed key packages, allowing members to be added to a group while offline.
• Customizable credential system with built in support for X.509 certificates.
• Extension system allowing for application specific data to be negotiated via the protocol.
• Strong forward secrecy and post compromise security.
• Crypto agility via support for multiple cipher suites.
• Pre-shared key support.
• Subgroup branching.
• Group reinitialization for breaking changes such as protocol upgrades.

Features

• Easy to use client interface that can manage multiple MLS identities and groups.
• 100% RFC 9420 conformance with support for all default credential, proposal, and extension types.
• Support for WASM builds.
• Configurable storage for key packages, secrets and group state via traits along with provided “in memory” and SQLite implementations.
• Support for custom user proposal and extension types.
• Ability to create user defined credentials with custom validation routines that can bridge to existing credential schemes.
• OpenSSL and Rust Crypto based cipher suite implementations.
• Crypto agility with support for user defined cipher suite.
• Extensive test suite including security and interop focused tests against pre-computed test vectors.

Crypto Providers

For cipher suite descriptions see the RFC documentation here

Name	Cipher Suites	X509 Support
OpenSSL	1-7	Stable
AWS-LC	1,2,3,5,7	Stable
Rust Crypto	1,2,3	⚠️ Experimental

Security Notice

This library has been validated for conformance to the RFC 9420 specification but has not yet received a full security audit by a 3rd party.

Re-exports

pub use crate::client::Client;

pub use crate::group::mls_rules::MlsRules;

pub use crate::group::Group;

pub use mls_rs_codec;

Modules

client

client_builder

Definitions to build a Client.

crypto

Dependencies of CryptoProvider and CipherSuiteProvider

error

Error types.

extension

Extension utilities and built-in extension types.

external_clientexternal_client

Tools to observe groups without being a member, useful for server implementations.

group

E2EE group created by a Client.

identity

Identity providers to use with ClientBuilder.

mls_rules

Dependencies of MlsRules.

psk

Pre-shared key support.

storage_provider

Storage providers to use with ClientBuilder.

time

WASM compatible timestamp.

Structs

CipherSuite

Wrapper type representing a ciphersuite identifier along with default values defined by the MLS RFC. Custom ciphersuites can be defined using a custom CryptoProvider.

Extension

An MLS protocol extension.

ExtensionList

A collection of MLS Extensions.

KeyPackage

KeyPackageRef

MlsMessage

A MLS protocol message for sending data over the wire.

ProtocolVersion

Wrapper type representing a protocol version identifier.

Enums

MlsMessageDescription

WireFormat

Content description of an MlsMessage

Traits

CipherSuiteProvider

Provides all cryptographic operations required by MLS for a given cipher suite.

CryptoProvider

Provides implementations for several ciphersuites via CipherSuiteProvider.

GroupStateStorage

Storage that can persist and reload a group state.

IdentityProvider

Identity system that can be used to validate a SigningIdentity

KeyPackageStorage

Storage trait that maintains key package secrets.

PreSharedKeyStorage

Storage trait to maintain a set of pre-shared key values.