OpenSSL

OpenSSL is an open source implementation of the SSL and TLS protocols. The core library (written in the C programming language) implements the basic cryptographic functions and provides various utility functions. Wrappers allowing the use of the OpenSSL library in a variety of computer languages are available.

Versions are available for most Unix-like operating systems, including Linux and Mac OS X. OpenSSL is based on SSLeay by Eric Young and Tim Hudson.

GnuTLS is an alternative to OpenSSL, GPL-compatible whereas OpenSSL is not .

The Open Source Software Institute is attempting to secure a FIPS 140-2 validation for OpenSSL .