authentication – (DOD) 1. 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. Referenced in ATP 3-50.10, ATP 3-50.22, ATP 6-02.53. 2. A means of identifying individuals and verifying their eligibility to receive specific categories of information. Referenced in ATP 3-50.10, ATP 3-50.22, ATP 6-02.53. 3. Evidence by proper signature or seal that a document is genuine and official. Referenced in ATP 3-50.10, ATP 3-50.22, ATP 6-02.53. 4. In personnel recovery missions, the process whereby the identity of an isolated person is confirmed. (JP 3-50) Referenced in ATP 3-50.3, ATP 3-50.10, ATP 3-50.22, ATP 6-02.53.