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X.509
X.509
In the field of cryptography, X.509 is a user-proclaimed standard of the PKI (Public-Key Infrastructure). It specifies standard formats for digital certificates and several cryptographic algorithms. The X.509 system calls for a CA (Certificate Authority) to issue a digital certificate. That certificate is what binds a specific organization or individual to an email address or website.
X.509 allows a trusted root certificate to be distributed amongst various network associates so that they can use the organization’s PKI system. Web browsers such as Internet Explorer, Navigator, Safari and Opera come pre-installed with root certificates. This enables a site owner or network administrator to determine what CAs are to be trusted.
The X.509 system also consists of standards for CRL (certificate revocation list) implementation, an aspect of the PKI system that is often neglected.
Since X.509 has yet to made official, the OCSP (Online Certificate Status Protocol) is the method approved by the IETF for checking the validity of digital certificates.