1. A security authority trusted by communicating entities with respect to specific security-related activities (e.g., for the purpose of authentication. ) 2. A security authority or its agent, trusted by other entities with respect to security-related activities. 3. A security authority or its agent, trusted by other entities with respect to security-related activities. In the context of this standard a trusted third party is trusted by a claimant and/or verifier for the purposes of authentication.