The TScCertKeyUsageExtension class represents the certificate key usage extension that uses the flags in the TScKeyUsageFlag enumeration to define key usage.
A certificate lets a subject to perform certain tasks. In order to control usage of a certificate out of designated scopes, the corresponding restrictions are automatically included in the certificate. The Key Usage extension is a restriction method that determines, for what purposes the certificate can be used. This lets to produce certificates that can be used both for tasks restricted by certain scopes, and for different tasks.
This extension is specified in RFC 5280 section 188.8.131.52.