The CA is responsible for managing the certificate throughout its life cycle. Key elements or subcomponents of
the CA structure include the certification practice statement (CPS), RAs and certificate revocation lists (CRLs).
• Registration authority—An RA is an authority in a network that verifies user requests for a digital certificate
and tells the CA to issue it. An optional entity separate from a CA, an RA would be used by a CA with a very
large customer base. CAs use RAs to delegate some of the administrative functions associated with recording
or verifying some or all of the information needed by a CA to issue certificates or CRLs and to perform other
certificate management functions. However, with this arrangement, the CA still retains sole responsibility for
signing either digital certificates or CRLs. RAs are part of a PKI. The digital certificate contains a public key that is used to encrypt messages and verify digital signatures. If an RA is not present in the PKI structure established, the CA is assumed to have the same set of capabilities as those defined for an RA. The administrative functions that a particular RA implements will vary based on the needs of the CA, but must support the principle of establishing or verifying the identity of the subscriber. These functions may include the following:
- Verifying information supplied by the subject (personal authentication functions)
- Verifying the right of the subject to requested certificate attributes
- Verifying that the subject actually possesses the private key being registered and that it matches the public key requested for a certificate (generally referred to as proof of possession [POP])
- Reporting key compromise or termination cases where revocation is required
- Assigning names for identification purposes
- Generating shared secrets for use during the initialization and certificate pick-up phases of registration
- Initiating the registration process with the CA on behalf of the subject end entity
- Initiating the key recovery processing
- Distributing the physical tokens (such as smart cards) containing the private keys
- Certificate revocation list—The CRL is an instrument for checking the continued validity of the certificates
for which the CA has responsibility. The CRL details digital certificates that are no longer valid because they
were revoked by the CA. The time gap between two updates is critical and is also a risk in digital certificates
verification.
- Certification practice statement—CPS is a detailed set of rules governing the CA’s operations. It provides an understanding of the value and trustworthiness of certificates issued by a given CA in terms of the following: . The controls that an organization observes
.The method it uses to validate the authenticity of certificate applicants .The CA’s expectations of how its certificates may be used