The OpenCA Project is a collaborative effort to develop a robust, full-featured and Open Source out-of-the-box Certification Authority implementing the most used protocols with full-strength cryptography world-wide. OpenCA is based on many Open-Source Projects. Among the supported software is OpenLDAP, OpenSSL, Apache Project, Apache mod_ssl.
The OpenCA OCSP Responder is an RFC 2560 compliant OCSPD responder. It can be used to verify the status of a certificate using OCSP clients (such as Mozilla/Netscape7). The Responder is actually included in the main OpenCA distribution package. It is also possible to install the daemon as a stand-alone application, in which case you will need a CRL (or access to an LDAP server where the CRL can be obtained).
The LibPKI Project is aimed to provide an easy-to-use PKI library for PKI-enabled application development. The library provides the developer with all the needed functionality to manage certificates, from generation to validation. It helps developers integrate X509 digital certificates into their applications, and implement complex cryptographic operations with a few simple function calls using a high-level cryptographic API. The library constitutes the core of other OpenCA Labs Projects like the PRQP Server, the OCSP Responder, and the OpenCA-NG PKI.