A user authentication system from RSA Security, Inc., Bedford, MA (www.securid.com) that uses a physical token people keep in their possession. The token's microprocessor and the server compute a number based on a secret key and the time of day. When individuals log in, they type in the number displayed on their tokens at that moment as an additional passcode. If the number matches the number that the SecurID authentication server computes, the user is presumed to be the valid holder of the card. See information security.