A system and method are disclosed for controlling physical access through a digital certificate validation process that works with standard certificate formats and that enables a certifying authority (CA) to prove the validity status of each certificate C at any time interval (e.g., every day, hour, or minute) starting with C's issue date, D.sub.1. C's time granularity may be specified within the certificate itself, unless it is the same for all certificates. For example, all certificates may have a one-day granularity with each certificate expires 365 days after issuance. Given certain initial inputs provided by the CA, a one-way hash function is utilized to compute values of a specified byte size that are included on the digital certificate and to compute other values that are kept secret and used in the validation process.