RFC 2560 (rfc2560) - Page 2 of 23

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RFC 2560                       PKIX OCSP                       June 1999


2.  Protocol Overview

   In lieu of or as a supplement to checking against a periodic CRL, it
   may be necessary to obtain timely information regarding the
   revocation status of a certificate (cf. [RFC 2459], Section 3.3).
   Examples include high-value funds transfer or large stock trades.

   The Online Certificate Status Protocol (OCSP) enables applications to
   determine the (revocation) state of an identified certificate. OCSP
   may be used to satisfy some of the operational requirements of
   providing more timely revocation information than is possible with
   CRLs and may also be used to obtain additional status information. An
   OCSP client issues a status request to an OCSP responder and suspends
   acceptance of the certificate in question until the responder
   provides a response.

   This protocol specifies the data that needs to be exchanged between
   an application checking the status of a certificate and the server
   providing that status.

2.1  Request

   An OCSP request contains the following data:

   -- protocol version
   -- service request
   -- target certificate identifier
   -- optional extensions which MAY be processed by the OCSP Responder

   Upon receipt of a request, an OCSP Responder determines if:

   1. the message is well formed

   2. the responder is configured to provide the requested service and

   3. the request contains the information needed by the responder If
   any one of the prior conditions are not met, the OCSP responder
   produces an error message; otherwise, it returns a definitive
   response.

2.2  Response

   OCSP responses can be of various types.  An OCSP response consists of
   a response type and the bytes of the actual response. There is one
   basic type of OCSP response that MUST be supported by all OCSP
   servers and clients. The rest of this section pertains only to this
   basic response type.




Myers, et al.               Standards Track