US 2010/0026529 A1 · Secure keypad scanning

Abstract

A secure key scanning functionality drives the row lines and column lines of a key switch array with randomized pulses of different polarities, and drives signals in one direction from a row line through a pressed key and to a column line as well as in an opposite direction from the column line through the pressed key and to the row line. To make unauthorized detecting of key presses more difficult, row lines and column lines are driven with pulses that appear as actual key press conditions when in fact the pulses are dummy pulses and no corresponding key has been pressed. In one novel aspect, dummy pulses are generated so that the line being driven with the dummy pulses has the same sustained and consistent waveform as the intersecting row and column lines that have identical waveforms due to the actual key press.

Claims24

Dependent claims

A method comprising:

(a) driving a first signal out onto a first row line, wherein the first row line is one of a plurality of row lines of a row line/column line matrix (RLCLM) of a key switch array;
(b) detecting the first signal on a first of a plurality of column lines of the RLCLM;
(c) driving a second signal out onto said first column line;
and
(d) detecting the second signal on first row line.

2 more elements

An integrated circuit comprising:

a plurality of input/output cells;
a plurality of terminals, wherein each terminal is coupled to a corresponding respective one of the plurality of input/output cells;
a memory that stores a set of processor-readable instructions, wherein the set of processor-readable instructions is a key scanning routine;
and
a processor that executes the set of processor-readable instructions such that:
1) a first pulse signal is driven out of a first of the input/output cells and a first of the terminals, and during the driving of the first pulse signal a second of the input/output cells is monitoring a second of the terminals to determine whether the first pulse signal is received on the second terminal, and 2) a second pulse signal is driven out of the second input/output cell and the second terminal, and during the driving of the second pulse signal the first input/output cell is monitoring the first terminal to determine whether the second pulse signal is received on the first terminal.

3 more elements

An integrated circuit comprising:

a memory that stores a set of processor-readable instructions, wherein the set of processor-readable instructions is a key scanning routine;
and
a processor that executes the set of processor-readable instructions;
a polarity bit;
an input/output bit;
an input read bit;
a terminal;
and
an input/output cell that is coupled to the terminal and that includes a logic circuit, wherein if the input/output bit has a first value then the logic circuit supplies either the value of the polarity bit or the inverse of the value of the polarity bit to the input read bit, whereas if the input/output bit has a second value then the logic circuit is usable to supply a value on the terminal to the input read bit.

6 more elements

Dependencies are inferred from the claim text.

Secure keypad scanning

Life of this patent

Secure keypad scanning

Life of this patent

Abstract

Claims24