04800590 is referenced by 196 patents and cites 13 patents.

A computer access system includes a password generator (10) and an lock computer (50) connected to receive passwords generated by the password generator and grant access to a host computer (52) when a password from the password generator (10) matches a password separately generated by the lock computer (50). The password generator (10) and the lock computer (50) have corresponding pseudo-random number sequences stored in memories (26 and 90). The password generator (10) and the lock computer (50) have synchronized clocks (30 and 84), which define time intervals. During a given time interval, entry of a personal identification number in password generator (10) will cause the password generator (10) to generate a unique password from the random number sequence in memory (26) and time interval information from clock (30). The user transmits the so-generated password to the lock computer (50), which independently generates a comparison password from the corresponding pseudo-random number sequence stored in memory (90), and the time interval defined by clock (84). If the passwords match, access to computer (52) is granted by the lock computer (50). Since the valid passwords change with each time interval, subsequent use of an intercepted password will not grant access to the computer.

Computer key and computer lock system
Application Number
Publication Number
Application Date
January 14, 1985
Publication Date
January 24, 1989
James C Vaughan
Palo Alto
Flehr Hohbach Test Albritton & Herbert
Willis E Higgins
G07P 7/00
H04K 1/00
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