Implementation of the proposed Messaging Layer Security protocol in C++. Depends on C++17, STL for data structures, and OpenSSL or BoringSSL for crypto.

MLSPP requires a few prerequisite libraries in order to fully build.

• nlohmann::json - Tested with latest versions.
• Cryptography Library - OpenSSL 1.1.1, OpenSSL 3.0, BoringSSL compatible (see details below)
• Catch2 - Only required when building the test suite.

The following should satisfy the prerequisites for these popular platforms. However, vcpkg is recommended for developer builds.

# Linux - Ubuntu 20.04, Ubuntu 22.04
$ sudo apt install libssl-dev nlohmann-json3-dev doctest-dev
# MacOs - Homebrew
$ brew install nlohmann-json doctest

A convenience Makefile is included to avoid the need to remember a bunch of CMake parameters. It will use vcpkg to satisfy all dependencies.

Note that on Windows the make commands should be run in PowerShell instead of cmd.exe, otherwise, vcpkg will report the error 'error: in triplet x64-windows: Unable to find a valid Visual Studio instance'.

> make        # Configures and builds the library 
> make dev    # Configure a "developer" build with tests and checks using OpenSSL 1.1
> make dev3   # Configure a "developer" build with tests and checks using OpenSSL 3.0
> make devB   # Configure a "developer" build with tests and checks using BoringSSL
> make test   # Builds and runs tests
> make format # Runs clang-format over the source

• Following Mozilla clang-format style. If you use the top-level Makefile (as suggested above), it will auto-format for you.
• General naming conventions:
  • Camel case for classes (RatchetNode)
  • Snake case for variables, functions, members (derive_epoch_keys)
  • Private member variables start with underscore (_)
  • In general, prefer descriptive names

MLS++ requires OpenSSL of at least version 1.1.1, or BoringSSL compatible with the same requirement. MLS++ is compatible with OpenSSL >= 3.0.

Pass OPENSSL_ROOT_DIR to guide CMake to select a specific OpenSSL/BoringSSL installation. You may also need to specify OPENSSL_INCLUDE_DIR, OPENSSL_CRYPTO_LIBRARY, and OPENSSL_SSL_LIBRARY depending on the file and folder structure of your installation. When manually passing OPENSSL_* options one should carefully verify that both the includes and libraries match the expected installation.