GnuTLS

According to Wikipedia:

GnuTLS (the GNU Transport Layer Security Library) is a free software implementation of the TLS, SSL and DTLS protocols. It offers an application programming interface (API) for applications to enable secure communication over the network transport layer, as well as interfaces to access X.509, PKCS #12, OpenPGP and other structures.

Installation

Install the gnutls package.

For integration with the Apache HTTP Server install mod_gnutls.

Usage

See certtool(1) for the command used in the following sections and the info document for the API documentation.

Generate an RSA private key

$ certtool -p --rsa --bits=keysize

Generate a certificate signing request

$ certtool -q --load-privkey private_key --outfile file

Generate a self-signed certificate

$ certtool -s --load-privkey private_key --outfile file