The most widely recognized public-key certificate format is that defined in the ISO X.509 standard, as shown below. The X.509 certificate format provides for certificate extensions, including standard extensions and private or community-defined extensions. Standard extensions are defined for various purposes, including key and policy information, subject and issuer attributes, and certification path constraints. If this is done, anyone who wants to verify a signature will have the certificate in hand. When multiple parties are involved, this can be a complex task.
Directories provide an easy way to search for and find certificates on the Web.
The decision to revoke a certificate is the responsibility of the issuing company, generally in response to a request from an authorized person. For added security, the CA will generally authenticate the source of any revocation request. Maintaining Control of Certificate Management Digital certificates must be issued by a trusted entity known as a Certificate Authority. Certificate Authorities typically offer a combination of cryptography technology, an infrastructure of highly secure facilities, and a specification of practices and liability that establish its ability to operate as a trusted third party. In today's dynamic business climate, many companies want to take advantage of the peace of mind of working with a CA, but also want to maintain strict control over the issuance and revocation of digital certificates.