According to my research on different professional requirements, I can say that based on the information provided within the question the term being describe in the question is called a Certificate Revocation List (CRL). This is (like defined in the question) a list of digital certificates that have been revoked by the issuing Certificate Authority, before they actually expire making them obsolete and letting anyone interested know that they should no longer be trusted. This list is usually looked at when someone runs across a signature and want to know if that person actually holds that certain certificate proving that they have the knowledge that is required.
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The answer and procedures of the exercise are attached in the following image.
Explanation
Please consider the data provided by the exercise. If you have any question please write me back. Is an opinion what contains the image. Judge it like it is.