Understanding Public-Key Infrastructure: Concepts, Standards, and Deployment Considerations

X.509

The X.509 [X.509] portion of the ISO and CCITT/ITU-T X.500 suite of standards is in many ways the single most important factor in the transition of PKI concepts from small, closed-network, trial environments to large, open deployments. As noted in Chapter 6, "Certificates and Certification," the concept of a certificate makes public-key technology feasible when the entities are, for the most part, unknown to each other. Therefore, to bring PKI to large multi-national corporations or to millions of Internet users, a useful certificate format was necessary. To allow interoperability among multiple tools and applications, a certificate format needed to be standardized and widely adopted. It is precisely this role that X.509 has played: ...