X509 is a standard for defining a DigitalCertificate. It is the signing system used for SSL.
Some useful documentation on X509 certificates: http://java.sun.com/products/jdk/1.2/docs/guide/security/cert3.html.
Some information about how to implement X509
This is also just an interesting read to find out why X509 is such a bizarre standard
Things that use X509 certificates:
AddToMe...