Convert README.rst to markdown

Olm

===

# Olm

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.rst>`_.

The specification of the Olm ratchet can be found in [docs/olm.md](docs/olm.md).

This library also includes an implementation of the Megolm cryptographic

ratchet, as specified in `<docs/megolm.rst>`_.

ratchet, as specified in [docs/megolm.md](docs/megolm.md).

Building

--------

## Building

To build olm as a shared library run either:

.. code:: bash

```bash

cmake . -Bbuild

cmake --build build

```

or:

.. code:: bash

```bash

make

```

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:

.. code:: bash

```bash

cd build/tests

ctest .

```

To run the tests when using make, run:

.. code:: bash

```bash

make test

```

To build the JavaScript bindings, install emscripten from http://kripken.github.io/emscripten-site/ and then run:

.. code:: bash

```bash

make js

```

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:

.. code:: bash

```bash

cd android

./gradlew clean assembleRelease

```

To build the Xcode workspace for Objective-C bindings, run:

.. code:: bash

```bash

cd xcode

pod install

open OLMKit.xcworkspace

```

To build the Python bindings, first build olm as a shared library as above, and

then run:

.. code:: bash

```bash

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 ``make``.

To build olm as a static library (which still needs libstdc++ dynamically) run

either:

.. code:: bash

```bash

cmake . -Bbuild -DBUILD_SHARED_LIBS=NO

cmake --build build

```

or

.. code:: bash

```bash

make static

```

The library can also be used as a dependency with CMake using:

.. code:: cmake

```cmake

find_package(Olm::Olm REQUIRED)

target_link_libraries(my_exe Olm::Olm)

```

Release process

---------------

## Release process

First: bump version numbers in ``common.mk``, ``CMakeLists.txt``,

``javascript/package.json``, ``python/olm/__version__.py``, ``OLMKit.podspec``,

It's probably sensible to do the above on a release branch (``release-vx.y.z``

by convention), and merge back to master once the release is complete.

.. code:: bash

```bash

make clean

# build and test C library

pod trunk push OLMKit.podspec --use-libraries --allow-warnings

# Check the pod has been successully published with:

pod search OLMKit

```

Design

------

## Design

Olm is designed to be easy port to different platforms and to be easy

to write bindings for.

advantage, and new functionality is being added in C, with C++ parts being

rewritten as the need ariases.

Error Handling

~~~~~~~~~~~~~~

### Error Handling

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.

Random Numbers

~~~~~~~~~~~~~~

### Random Numbers

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.

Memory

~~~~~~

### Memory

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.

Output Encoding

~~~~~~~~~~~~~~~

### Output Encoding

Binary output is encoded as base64 so that languages that prefer unicode

strings will find it easier to handle the output.

Dependencies

~~~~~~~~~~~~

### Dependencies

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.

Contributing

------------

Please see `<CONTRIBUTING.rst>`_ when making contributions to the library.

## Contributing

Security assessment

-------------------

Please see [CONTRIBUTING.md](CONTRIBUTING.md) when making contributions to the library.

## Security assessment

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

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/

Bug reports

-----------

## Bug reports

Please file bug reports at https://github.com/matrix-org/olm/issues

What's an olm?

--------------

## 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/

Legal Notice

------------

## Legal Notice

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