Abstract: An access control system is disclosed in which protected systems and corresponding portable password issuing devices both generate new authentic passwords by successively encrypting a stored password with a selected sequence of predefined encryption steps. The protected system generates and displays one or more random digits, selects an encryption sequence by appending the random digits to the user's personal identification number, and generates an authentic password by sequentially encrypting the user's previous password with encryption steps corresponding to each of the digits in the selected encryption sequence. The user generates a purported password by entering his PIN and the displayed random number(s) on the keyboard of his password issuing device, which responds to encrypting a stored previous password value with encryption steps corresponding to the user's keystrokes, and displaying a new password on its display.

Abstract: Method and apparatus are disclosed for controlling access to information borne by information records installed in information recorders, which information recorders constitute a part of at least one digital computer system. The digital computer system is an unmodified general purpose digital computer, and each authorized accessant is supplied with an access control kit including a password issuing device and a record adapted to be installed in one of the recorders of that digital computer system.