Certificates are ______documents attesting to the ______ of a public key to an individual or other entity. They allow verification of the claim that a given publickey does in fact belong to a given individual. Certificates help prevent some one from using a phony key to ______someone else. In their simplest form, Certificates contain a public key and a name. As commonly used, a certificate also contains an ______ date, the name of the CA that issued the certificate, a serial number, and perhaps other information. Most importantly, it contains the digital ______ of the certificate issuer. The most widely accepted format for certificates is X.509 , thus, Certificates can be read or written by any application complying with X.509.