Why are there multiple trust hierarchies?
Several digital ID hierarchies (domains) have been established to ensure a common level of identity and confidence for all digital ID certificates within the domains. Two of the most popular domains, with thousands of existing customers, are the Commercial Hierarchy (digital ID certificates for users) and the Secure Server Hierarchy (digital ID certificates for specific servers used in Electronic Data Interchange and Electronic Commerce). Universities, corporations, and other entities may find it useful to establish their own hierarchies.