What is "openssl"

The Openssl is an open source implementation of SSL and TLS protocols.

The library (written in the C language) implements the basic encryption functions and provides various utility functions. Also available are Wrappers that allow the use of this library in various other languages.

It is available for most Unix-like systems, including Linux, Mac OS X, the four open source BSD versions, and also for Microsoft Windows. Openssl is based on Ssleay by Eric Young and Tim Hudson.

_{Source: Wikipedia}