Magic Number - Uwe Gradenegger

Force domain controller (or other participants) to use an online responder (OCSP)

By default, Windows systems, even if an online responder (OCSP) is configured, will be sent to a certain number of OCSP requests fall back to a (if available) brevocation list, because this is usually more efficient in such a case. However, this behavior is not always desired.

For example, if one uses smart card logins, one might want to know if Logins were executed with unauthorized issued certificates. In conjunction with the deterministic good of the online responder you can thus create an (almost) seamless Audit trail create for all smartcard logins.

Configure the "Magic Number" for the online responder

Even if an online responder is present in the network and the certification authorities have entered its address in the Authority Information Access (AIA) extension of the issued certificates, it is not always guaranteed that the online responder is actually used.

One variable here is the "Magic Number", which is present on every Windows operating system. It causes the system to fall back to blacklists (if present) if requests are made too often via OCSP for the same certificate authority.

Configure deterministic "good" for the online responder (OCSP).

In the default configuration, the online responder returns the status "Good" for requested certificates that do not appear on one of the configured revocation lists.

This can be problematic because the online responder has no knowledge of certificates issued by the certification authorities. If an attacker succeeds in issuing a certificate using the private key of the certification authority without their knowledge, this would not be detected by the online responder, and would also be reported in the Audit log show up as "Good".