A certificate authority (CA) issues, catalogs, renews, and revokes certificates under the management of a policy and administrative control. There is no need either to purchase third-party product to do so, or to purchase individual certificates from public CAs. (There may, however, be additional reasons to do that, such as to obtain an SSL certificate for a public e-commerce site.) Newer versions of Windows Server have continued to provide CA services and to add functionality. For example, Windows Server 2003 Enterprise CAs offer version2 certificate templates and Windows 2008 Enterprise CAs offer version 3 certificate templates to allow for further control and customization.