included, this value SHALL be provided as an OCSP singleExtensions
   extension identified by id-pkix-ocsp-archive-cutoff and of syntax
   GeneralizedTime.

   id-pkix-ocsp-archive-cutoff  OBJECT IDENTIFIER ::= { id-pkix-ocsp 6 }

   ArchiveCutoff ::= GeneralizedTime

   To illustrate, if a server is operated with a 7-year retention
   interval policy and status was produced at time t1 then the value for
   ArchiveCutoff in the response would be (t1 - 7 years).

4.4.5  CRL Entry Extensions

   All the extensions specified as CRL Entry Extensions - in Section 5.3
   of [RFC2459] - are also supported as singleExtensions.

4.4.6  Service Locator

   An OCSP server may be operated in a mode whereby the server receives
   a request and routes it to the OCSP server which is known to be
   authoritative for the identified certificate.  The serviceLocator
   request extension is defined for this purpose.  This extension is
   included as one of the singleRequestExtensions in requests.





 
RFC 2560                       PKIX OCSP                       June 1999


   id-pkix-ocsp-service-locator OBJECT IDENTIFIER ::= { id-pkix-ocsp 7 }

   ServiceLocator ::= SEQUENCE {
       issuer    Name,
       locator   AuthorityInfoAccessSyntax OPTIONAL }

   Values for these fields are obtained from the corresponding fields in
   the subject certificate.

5.  Security Considerations

   For this service to be effective, certificate using systems must
   connect to the certificate status service provider. In the event such
   a connection cannot be obtained, certificate-using systems could
   implement CRL processing logic as a fall-back position.

   A denial of service vulnerability is evident with respect to a flood
   of queries. The production of a cryptographic signature significantly
   affects response generation cycle time, thereby exacerbating the
   situation. Unsigned error responses open up the protocol to another
   denial of service attack, where the attacker sends false error
   responses.

   The use of precomputed responses allows replay attacks in which an
   old (good) response is replayed prior to its expiration date but
   after the certificate has been revoked. Deployments of OCSP should
   carefully evaluate the benefit of precomputed responses against the
   probability of a replay attack and the costs associated with its
   successful execution.

   Requests do not contain the responder they are directed to. This
   allows an attacker to replay a request to any number of OCSP
   responders.

   The reliance of HTTP caching in some deployment scenarios may result
   in unexpected results if intermediate servers are incorrectly
   configured or are known to possess cache management faults.
   Implementors are advised to take the reliability of HTTP cache
   mechanisms into account when deploying OCSP over HTTP.













 
RFC 2560                       PKIX OCSP                       June 1999


6.  References

   [RFC2459] Housley, R., Ford, W., Polk, W. and D. Solo, "Internet
             X.509 Public Key Infrastructure Certificate and CRL
             Profile", RFC 2459, January 1999.

   [HTTP]    Fielding, R., Gettys, J., Mogul, J., Frystyk, H. and T.
             Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC
             2068, January 1997.

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate