The term Liveness here refers to the need to ensure that the data used to make an authorization check is valid at the time of the check.
The mistake I made with PKI tokens was in not realizing how important Liveness was. The mistake was based on the age old error of confusing authentication with authorization. Since a Keystone token is used for both, I was confused into thinking that the primary importance was on authentication, but the reality is that the most important thing a token tells you is information essential to making an authorization decision. Continue reading