### 4.9.9 On-line revocation/status checking availability The validity interval of an OCSP response is the difference in time between the `thisUpdate` and `nextUpdate` field, inclusive. For purposes of computing differences, a difference of 3,600 seconds shall be equal to one hour, and a difference of 86,400 seconds shall be equal to one day, ignoring leap-seconds. A certificate serial is "assigned" if: - a Certificate or Precertificate with that serial number has been issued by the Issuing CA; or - a Precertificate with that serial number has been issued by a Precertificate Signing Certificate, as defined in [Section 7.1.2.4](#7124-technically-constrained-precertificate-signing-ca-certificate-profile), associated with the Issuing CA. A certificate serial is "unassigned" if it is not "assigned". The following SHALL apply for communicating the status of Certificates and Precertificates which include an Authority Information Access extension with an id-ad-ocsp accessMethod. OCSP responders operated by the CA SHALL support the HTTP GET method, as described in RFC 6960 and/or RFC 5019. The CA MAY process the Nonce extension (`1.3.6.1.5.5.7.48.1.2`) in accordance with RFC 8954. For the status of a Subscriber Certificate or its corresponding Precertificate: - Effective 2025-01-15, an authoritative OCSP response MUST be available (i.e. the responder MUST NOT respond with the "unknown" status) starting no more than 15 minutes after the Certificate or Precertificate is first published or otherwise made available. - For OCSP responses with validity intervals less than sixteen hours, the CA SHALL provide an updated OCSP response prior to one-half of the validity period before the nextUpdate. - For OCSP responses with validity intervals greater than or equal to sixteen hours, the CA SHALL provide an updated OCSP response at least eight hours prior to the nextUpdate, and no later than four days after the thisUpdate. For the status of a Subordinate CA Certificate, the CA SHALL provide an updated OCSP response at least every twelve months, and within 24 hours after revoking the Certificate. The following SHALL apply for communicating the status of *all* Certificates for which an OCSP responder is willing or required to respond. OCSP responses MUST conform to RFC6960 and/or RFC5019. OCSP responses MUST either: 1. be signed by the CA that issued the Certificates whose revocation status is being checked, or 2. be signed by an OCSP Responder which complies with the OCSP Responder Certificate Profile in [Section 7.1.2.8](#7128-ocsp-responder-certificate-profile). OCSP responses for Subscriber Certificates MUST have a validity interval greater than or equal to eight hours and less than or equal to ten days. If the OCSP responder receives a request for the status of a certificate serial number that is "unassigned", then the responder SHOULD NOT respond with a "good" status. If the OCSP responder is for a CA that is not Technically Constrained in line with [Section 7.1.2.3](#7123-technically-constrained-non-tls-subordinate-ca-certificate-profile) or [Section 7.1.2.5](#7125-technically-constrained-tls-subordinate-ca-certificate-profile), the responder MUST NOT respond with a "good" status for such requests.