Lime

Lime is a C++ library implementing Open Whisper System Signal protocol : Sesame, double ratchet and X3DH. https://signal.org/docs/

Lime can run the Signal Protocol using elliptic curve 25519 or curve 448-goldilocks.

It is designed to work jointly with Linphone[1] in a multiple devices per user and multiple users per device environment.

Dependencies

• bctoolbox[2] : portability layer, built with Elliptic Curve Cryptography
• soci-sqlite3 : Db access

Build instrucitons

 cmake -DCMAKE_INSTALL_PREFIX=<install_prefix> -DCMAKE_PREFIX_PATH=<search_prefix> <path_to_source>

 make
 make install

Documentation

To generate the Doxygen documentation files(having ran the cmake command):

 make doc

Comprehensive documentation on implementation choices and built-in protocols in lime.pdf

Testing

To test on local machine, you must run a local X3DH server.

• A nodejs/sqlite version of UNSECURE X3DH server is provided in tester/server/nodejs See README from this directory for instructions.

• A php/mysql (on docker) version of UNSECURE X3DH server is provided in tester/server/php See README from this directory for instructions.

Library settings

Some mostly harmless settings are available in src/lime_settings.hpp

Library API

The C++11 API is available in include/lime/lime.hpp

if enabled (see Options), a C89 FFI is provided by include/lime/lime_ffi.h

Options

• CMAKE_INSTALL_PREFIX=<string> : installation prefix
• CMAKE_PREFIX_PATH=<string> : prefix where depedencies are installed
• ENABLE_UNIT_TESTS=NO : do not compile non-regression tests
• ENABLE_SHARED=NO : do not build the shared library.
• ENABLE_STATIC=NO : do not build the static library.
• ENABLE_STRICT=NO : do not build with strict complier flags e.g. -Wall -Werror
• ENABLE_Curve25519 : Enable support of Curve 25519.
• ENABLE_Curve448 : Enable support of Curve 448.
• ENABLE_PROFILING : Enable code profiling for GCC
• ENABLE_C_INTERFACE : Enable support of C89 foreign function interface

• [1] linphone-desktop: git://git.linphone.org/linphone-desktop.git
• [2] bctoolbox: git://git.linphone.org/bctoolbox.git or http://www.linphone.org/releases/sources/bctoolbox