Keypad device security system and method
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United States of America Patent
Stats
-
Feb 20, 2007
Grant Date -
N/A
app pub date -
May 8, 2001
filing date -
May 8, 2001
priority date (Note) -
Expired
status (Latency Note)
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Abstract
The present invention increases the difficulty of interpreting electromagnetic emissions from a keypad system by facilitating randomness in the electromagnetic emissions associated with a particular key activation. A keypad security circuit utilizes a set of digital values that varies over both time and the bits as a keypad driver word applied to a keypad attribute (e.g., a row or column). The keypad security system of the present invention drives the varying strong keypad driver signal to an attribute of a keypad switch matrix (e.g., the rows or columns), applies an independently configured weak driver signals to the opposing attribute of the keypad switch matrix, retrieves a resulting signal from the opposing attribute, and interprets the results to determine if a switch included in a keypad system was activated (e.g., a key is pressed).
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