OpenSSL

OpenSSL is a robust, commercial-grade toolkit and general-purpose cryptography library for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. The library allows for secure communications over computer networks against eavesdropping. It is widely used for internet-based servers where the most common use-case is HTTPS for websites. OpenSSL is licensed under an Apache-style license is free to use for non-commercial and commercial projects alike.