OCSP Stapling - Solution

Solution

OCSP stapling resolves both problems in a fashion reminiscent of the Kerberos Ticket. In a stapling scenario, the certificate holder queries the OCSP server themselves at regular intervals, obtaining a signed time-stamped OCSP response. When the site's visitors attempt to connect to the site, this response is included ("stapled") with the TLS/SSL Handshake via the Certificate Status Request extension response (note: the TLS client must explicitly include a Certificate Status Request extension in its ClientHello TLS/SSL handshake message). It may appear that allowing the site operator to control verification responses introduces an opportunity for fraud. Since the response is signed by the certificate authority, not the certificate holder, though, and since lack of a valid stapled response will just cause the client to ask the OCSP server directly, there is actually no increased risk with this approach.

As a result, clients continue to have verifiable assurance from the certificate authority that the certificate is presently valid (or was quite recently), but no longer need to individually contact the OCSP server. This means that the brunt of the resource burden is now placed back on the certificate holder. It also means that the client software no longer needs to disclose users' browsing habits to any third party.

Overall performance is also improved: When the client fetches the OCSP response directly from the CA, it usually involves the lookup of the domain name of the CA's OCSP server in the DNS as well as establishing a connection to the OCSP server. When OCSP stapling is used, the certificate status information is delivered to the client through the channel already established causing no additional delay.