An identification tag (100) facilitates use of a secure computer system (300). The tag (100) is adapted to be worn on a user's wrist and includes an identification and registration circuit (102) that includes an identification component (106), an affiliation component (110), and a light-emitting diode (112). The computer system includes an RF identification tag registration device (302) operable to acquire user physical information and communicate the physical information to a computer (202), wherein the computer verifies that a valid user is wearing the tag (100). The identification and registration device (302) ensures that the physical information communicated to the computer pertains to the user wearing the tag by comparing pulse signals acquired from the user's hand and wrist as the device (302) is acquiring physical information. The computer (202) uses the identification information and the affiliation information to log the user into and out of the system (300), and to associate the identification information with a particular user.