Chapter 2. Introduction to Red Hat Certificate System

Every common PKI operation, such as issuing, renewing, and revoking certificates; archiving and recovering keys; publishing CRLs and verifying certificate status, is carried out by interoperating subsystems within Red Hat Certificate System. The functions of each individual subsystem and the way that they work together to establish a robust and local PKI is described in this chapter.

2.1. A Review of Certificate System Subsystems

Red Hat Certificate System provides five different subsystems, each focusing on different aspects of a PKI deployment:
  • A certificate authority called Certificate Manager. The CA is the core of the PKI; it issues and revokes all certificates. The Certificate Manager is also the core of the Certificate System. By establishing a security domain of trusted subsystems, it establishes and manages relationships between the other subsystems.
  • A key recovery authority (KRA). Certificates are created based on a specific and unique key pair. If a private key is ever lost, then the data which that key was used to access (such as encrypted emails) is also lost because it is inaccessible. The KRA stores key pairs, so that a new, identical certificate can be generated based on recovered keys, and all of the encrypted data can be accessed even after a private key is lost or damaged.


    In previous versions of Certificate System, KRA was also referred to as the data recovery manager (DRM). Some code, configuration file entries, web panels, and other resources might still use the term DRM instead of KRA.
  • An online certificate status protocol (OCSP) responder. The OCSP verifies whether a certificate is valid and not expired. This function can also be done by the CA, which has an internal OCSP service, but using an external OCSP responder lowers the load of the issuing CA.
  • A token key service (TKS). The TKS derives keys based on the token CCID, private information, and a defined algorithm. These derived keys are used by the TPS to format tokens and enroll certificates on the token.
  • A token processing system (TPS). The TPS interacts directly with external tokens, like smart cards, and manages the keys and certificates on those tokens through a local client, the Enterprise Security Client (ESC). The ESC contacts the TPS when there is a token operation, and the TPS interacts with the CA, KRA, or TKS, as required, then send the information back to the token by way of the Enterprise Security Client.
Even with all possible subsystems installed, the core of the Certificate System is still the CA (or CAs), since they ultimately process all certificate-related requests. The other subsystems connect to the CA or CAs likes spokes in a wheel. These subsystems work together, in tandem, to create a public key infrastructure (PKI). Depending on what subsystems are installed, a PKI can function in one (or both) of two ways:
  • A token management system or TMS environment, which manages smart cards. This requires a CA, TKS, and TPS, with an optional KRA for server-side key generation.
  • A traditional non token management system or non-TMS environment, which manages certificates used in an environment other than smart cards, usually in software databases. At a minimum, a non-TMS requires only a CA, but a non-TMS environment can use OCSP responders and KRA instances as well.