| 摘要 |
A method of operating a security system includes accessing a database and obtaining a user PIN. A normal keypad is defined in which a plurality of alphanumeric characters are displayed in defined normal positions. A scrambled keypad is also defined including the PIN so that at least some of a plurality of alphanumeric characters are displayed on the scrambled keypad in positions which are different to the positions in which they would be displayed in the defined normal keypad. In addition, for each of the alphanumeric characters of the PIN the alphanumeric character which is normally displayed in the normal keypad in the position in which the alphanumeric characters of the PIN are displayed in the scrambled keypad is determined thereby to arrive at a scrambled PIN Data defining the scrambled keypad is then transmitted to a user over a first communications network.
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