| 摘要 |
In a method of preventing unauthorised access to information inputted by key depressions on a keyboard (21), e.g. PIN codes inputted in a cash dispenser, and transferred from the keyboard in the form of electric signals on electric lines (d0-d3) to a computer (23) processing the information, the computer (23) receives signals from the lines during specific receiving periods, and between these periods the computer transmits, on the said lines, signals which simulate the depressions. The duration and frequency of these simulated key prevent an unauthorised line tapper from distinguishing simulated key depressions from genuine depressions. <IMAGE> |
