Certification validation: Back to the past

In MBarka and Stern (2011) [3], we proposed a new algorithm to validate certificates in the past with the goals of it being simple to present, simple to implement and to fall back on standard algorithms with current time settings. This paper improves our algorithm through a much cleaner handling of time issues by defining a new notion, called revocation freshness, yielding a better fall-back on the standard algorithm. It also takes into account a practical ''caution period'' to lessen some of our previous hypothesis.