A Smart Card is a credit-card-sized hardware device used in a cryptographic Authentication system. Some Smart Card's operate on the basis of a frequently changing code: a User who wishes to Login must enter his own User ID and the current code displayed by the card. An alternate system uses a cryptographic calculator, where the user logs into a system, which displays a challenge string. The User keys this string into his own Smart Card, which prints a response. The response is used as the User's password for the Login Session.