Certificate Revocation

Once a certificate revocation is requested, a message is returned to the user indicated the result of the activity. An example of this is shown in Figure 9 below. When a certificate is revoked, its serial number is placed on the Certificate Revocation List (CRL). For a refresher on CRLs, please see Growing A Tree Of Trust - Part One. CRLs are checked each time a certificate''s use is requested, and if it''s listed, access is denied. The message that''s often return when the use of a revoked certificate is attempted appears below in Figure 10.

Figure 9
Certificate Revocation Request

Figure 10
Access Denied!

Now that you''ve seen how digital certificates are requested, issued, used, and revoked from the end-user point of view, you can begin to gain a sense of what''s needed for background processing and the levels of security that are required. It''s no great wonder why so many organizations that have tried to serve their own CA function often turn to those with high expertise in the field.

Next time we''ll take a close look at some major CA service providers that can help you to build your PKI. Stay tuned!