Question

Why do we need certificate revocation? What approaches do you know for it?

Answer 1

Certificate revocation is necessary to maintain the security and trustworthiness of digital certificates. The main approaches used for certificate revocation are Certificate Revocation Lists (CRL), Online Certificate Status Protocol (OCSP), and Delta CRLs.

Step-by-step explanation:

Certificate revocation is necessary to ensure the security and trustworthiness of digital certificates. Certificates are used to verify the identity of a website or entity online. However, there may be instances where a certificate becomes compromised, expires, or the entity is no longer trustworthy. In such cases, certificate revocation allows the certificate authority to invalidate the certificate, preventing its further use.

There are several approaches to certificate revocation:

1. Certificate Revocation Lists (CRL): A CRL is a list maintained by the certificate authority that includes the serial numbers of revoked certificates. Clients can check the CRL to verify if a certificate has been revoked.
2. Online Certificate Status Protocol (OCSP): OCSP provides real-time certificate status information. Instead of downloading the entire CRL, clients send a request to the OCSP server to check the revocation status of a specific certificate.
3. Delta CRLs: To reduce the overhead of downloading large CRLs, delta CRLs contain incremental updates of revoked certificates since the last full CRL was published. Delta CRLs are more efficient for clients to update their revocation information.