GnuTLS is a project that aims to develop a library
which provides a secure layer, over a reliable transport layer.
Currently the GnuTLSlibrary implements the proposed
standards by the IETF's TLS working group.
Network Security Services (NSS) is a set of libraries designed to support
cross-platform development of security-enabled client and server applications.
Applications built with NSS can support SSL v2 and v3, TLS, PKCS #5, PKCS
#7, PKCS #11, PKCS #12, S/MIME, X.509 v3 certificates, and other security
standards.