1. Security measure designed to establish the validity of a transmission, message, or originator, or a means of verifying an individual's authorization to receive specific categories of information. 2. A security measure designed to protect a communications system against acceptance of a fraudulent transmission or simulation by establishing the validity of a transmission, message, or originator. 3. Evidence by proper signature or seal that a document is genuine and official. 4. The verification of a claimed identity. Example: By the use of a password. 5. The process by which the identity of an entity is established. 6. See data origin authentication, and peer entity authentication. Note: In this part of 7498 the term "authentication" is not used in connection with data integrity; the term "data integrity" is used instead. The property of knowing that the data received is the same as the data that was sent, and that the claimed sender is in fact the actual sender.