Online Certificate Status Protocol (OCSP)
Since CRLs are issued periodically, they do not provide a real time information about the status of certificates. In cases like financial operations where real time validation is required, using CRLs as the source of revocation information is not considered to be secure enough and unacceptable. As a remedy, Online Certificate Status Protocol (OCSP) is used.
A simple scenario demonstrating the operation of the system is as follows: User Reques: What is the status of the certificate with the serial number 10 ?
The response of the OCSP server may be one of the following: The status of the certificate is :
- Good (not revoked)
- Bad (revoked)
- Revocation reason
- Revocation time
- Unknown
There may be one or more OCSP server for each CA. OCSP servers can access the revocation status information of the certificates that their CAs have issued and give response to the incoming OCSP requests. The integrity of the OCSP responses are protected via electronic signature.
