Network Security Services (NSS) is a set of libraries designed to support
cross-platform development of security-enabled 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.

WWW: http://www.mozilla.org/projects/security/pki/nss/