OpenSSL is a general purpose cryptography library that provides an open source implementation of the Secure Sockets Layer (SSL) and Transport Layer Security (TLS) protocols.

The library includes tools for generating RSA private keys and Certificate Signing Requests (CSRs), checksums, managing certificates and performing encryption/decryption. OpenSSL is written in C, but wrappers are available for a wide variety of computer languages.

It’s being used widely on many internet-facing devices, including two thirds of all web servers.