An implementation of the Double Ratchet cryptographic ratchet described by https://whispersystems.org/docs/specifications/doubleratchet/, written in C and C++11 and exposed as a C API.
The specification of the Olm ratchet can be found in docs/olm.md.
This library also includes an implementation of the Megolm cryptographic ratchet, as specified in docs/megolm.md.
To build olm as a shared library run either:
cmake . -Bbuild cmake --build build
Using cmake is the preferred method for building the shared library; the Makefile may be removed in the future.
To run the tests when using cmake, run:
cd build/tests ctest .
To run the tests when using make, run:
Note that if you run emscripten in a docker container, you need to pass through the EMCC_CLOSURE_ARGS environment variable.
To build the android project for Android bindings, run:
cd android ./gradlew clean assembleRelease
To build the Xcode workspace for Objective-C bindings, run:
cd xcode pod install open OLMKit.xcworkspace
To build the Python bindings, first build olm as a shared library as above, and then run:
cd python make
to make both the Python 2 and Python 3 bindings. To make only one version, use
make olm-python2 or
make olm-python3 instead of just
To build olm as a static library (which still needs libstdc++ dynamically) run either:
cmake . -Bbuild -DBUILD_SHARED_LIBS=NO cmake --build build
The library can also be used as a dependency with CMake using:
find_package(Olm::Olm REQUIRED) target_link_libraries(my_exe Olm::Olm)
First: bump version numbers in
Also, ensure the changelog is up to date, and that everyting is committed to git.
It's probably sensible to do the above on a release branch (
by convention), and merge back to master once the release is complete.
Olm is designed to be easy port to different platforms and to be easy to write bindings for.
It was originally implemented in C++, with a plain-C layer providing the public API. As development has progressed, it has become clear that C++ gives little advantage, and new functionality is being added in C, with C++ parts being rewritten as the need ariases.
All C functions in the API for olm return
olm_error() on error.
This makes it easy to check for error conditions within the language bindings.
Olm doesn't generate random numbers itself. Instead the caller must provide the random data. This makes it easier to port the library to different platforms since the caller can use whatever cryptographic random number generator their platform provides.
Olm avoids calling malloc or allocating memory on the heap itself. Instead the library calculates how much memory will be needed to hold the output and the caller supplies a buffer of the appropriate size.
Binary output is encoded as base64 so that languages that prefer unicode strings will find it easier to handle the output.
Olm uses pure C implementations of the cryptographic primitives used by the ratchet. While this decreases the performance it makes it much easier to compile the library for different architectures.
Please see CONTRIBUTING.md when making contributions to the library.
Olm 1.3.0 was independently assessed by NCC Group's Cryptography Services Practive in September 2016 to check for security issues: you can read all about it at https://www.nccgroup.trust/us/our-research/matrix-olm-cryptographic-review/ and https://matrix.org/blog/2016/11/21/matrixs-olm-end-to-end-encryption-security-assessment-released-and-implemented-cross-platform-on-riot-at-last/
Please file bug reports at https://github.com/matrix-org/olm/issues
What's an olm?
It's a really cool species of European troglodytic salamander. http://www.postojnska-jama.eu/en/come-and-visit-us/vivarium-proteus/
The software may be subject to the U.S. export control laws and regulations and by downloading the software the user certifies that he/she/it is authorized to do so in accordance with those export control laws and regulations.