This module uses the functions of OpenSSL for generation and verification of signatures and for sealing (encrypting) and opening (decrypting) data. PHP-4.0.4pl1 requires OpenSSL >= 0.9.6, but PHP-4.0.5 and greater with also work with OpenSSL >= 0.9.5.
OpenSSL offers many features that this module currently doesn't support. Some of these may be added in the future.