A system using digital certificates having overlapping validity intervals. The overlapping certificates can be used in a hierarchical certificate authorities network in order to obtain benefits such as to increase the usage of all the certificates in the certificate chain; reduce/eliminate the certificate updates/downloads to a large population; only replace the minimum number of certificates in the trust hierarchy to re-establish the certificate chain; reduce the complexity of maintaining certificate nesting in certificate generation process; reduce the risk of service interruption; and control the extent of older technology in circulation and to reduce the risk associated with older products being more susceptible to attack. The certificate renewal process of a preferred embodiment is described.