Koninklijke Philips Corporation N.v.

Nxp B.v.

Rajeev Sethia

Mark Leonard Buer

Franklyn H Story

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).

Keypad device security system and method

A power management system permits power-reduced operation of selected circuit blocks in a manner that requires no modification to other bus-coupled circuit blocks attempting to communicate with such selected circuit blocks. Consistent with one embodiment of the present invention, the approach is implemented in a digital electronic circuit arrangement having an accessing circuit block coupled to a clocked circuit block over a data bus. The clocked circuit block is power managed by decreasing, e.g., reducing or blocking, the clock speed to the clocked circuit block which impedes its ability communicate over the data bus. Once the clocked circuit block is set in a reduced power mode, the bus is monitored for data-access communications from the accessing circuit block to the clocked circuit block. In response to such a communication, a substitute response is generated on the data bus, directed to the accessing circuit block, and the clock speed to the clocked circuit block, is increased and brought out of the reduced power mode for further communications with the accessing circuit block.

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Chandler, AZ, United States of America

Rajeev Sethia