OpenSSL

OpenSSL is a Secure Sockets Layer toolkit based on the SSLeay library. It supports Secure Sockets Layer (SSL) v2 and v3 specification and Transport Layer Security (TLS) v1.0/v1.1/v1.2 protocols but is also usable as a general purpose cryptography library.

Please note if you have been using older 0.9.x versions you may need to do some testing and possibly code re-factoring before using 1.x, since a few features were removed in the newer version.