The Horde_Crypt:: class provides an API for various cryptographic systems used by Horde applications.
Horde_Crypt_pgp:: provides a framework for Horde applications to interact with the GNU Privacy Guard program ("GnuPG"). GnuPG implements the OpenPGP standard (RFC 2440).
Horde_Crypt_smime:: provides a framework for Horde applications to interact with the OpenSSL library and implement S/MIME.