Patent Application
20140240283
1. Field of the Invention
This invention relates generally to touch sensors and secure digital communication pathways between components in a touch sensor that enable the secure entry of data to a touch sensor.
2. Description of Related Art
There are several designs for capacitance sensitive touch sensors. It is useful to examine the underlying technology to better understand how a capacitance sensitive touchpad may be modified to work with the present invention.
The CIRQUE® Corporation touchpad is a mutual capacitance-sensing device and an example is illustrated as a block diagram in
The CIRQUE® Corporation touchpad 10 measures an imbalance in electrical charge on the sense line 16. When no pointing object is on or in proximity to the touchpad 10, the touchpad circuitry 20 is in a balanced state, and there is no charge imbalance on the sense line 16. When a pointing object creates imbalance because of capacitive coupling when the object approaches or touches a touch surface (the sensing area 18 of the touchpad 10), a change in capacitance occurs on the electrodes 12, 14. What is measured is the change in capacitance, but not the absolute capacitance value on the electrodes 12, 14. The touchpad 10 determines the change in capacitance by measuring the amount of charge that must be injected onto the sense line 16 to reestablish or regain balance of charge on the sense line.
The system above is utilized to determine the position of a finger on or in proximity to a touchpad 10 as follows. This example describes row electrodes 12, and is repeated in the same manner for the column electrodes 14. The values obtained from the row and column electrode measurements determine an intersection which is the centroid of the pointing object on or in proximity to the touchpad 10.
In the first step, a first set of row electrodes 12 are driven with a first signal from P, N generator 22, and a different but adjacent second set of row electrodes are driven with a second signal from the P, N generator. The touchpad circuitry 20 obtains a value from the sense line 16 using a mutual capacitance measuring device 26 that indicates which row electrode is closest to the pointing object. However, the touchpad circuitry 20 under the control of some microcontroller 28 cannot yet determine on which side of the row electrode the pointing object is located, nor can the touchpad circuitry 20 determine just how far the pointing object is located away from the electrode. Thus, the system shifts by one electrode the group of electrodes 12 to be driven. In other words, the electrode on one side of the group is added, while the electrode on the opposite side of the group is no longer driven. The new group is then driven by the P, N generator 22 and a second measurement of the sense line 16 is taken.
From these two measurements, it is possible to determine on which side of the row electrode the pointing object is located, and how far away. Using an equation that compares the magnitude of the two signals measured then performs pointing object position determination.
The sensitivity or resolution of the CIRQUE® Corporation touchpad is much higher than the 16 by 12 grid of row and column electrodes implies. The resolution is typically on the order of 960 counts per inch, or greater. The exact resolution is determined by the sensitivity of the components, the spacing between the electrodes 12, 14 on the same rows and columns, and other factors that are not material to the present invention. The process above is repeated for the Y or column electrodes 14 using a P, N generator 24.
Although the CIRQUE® touchpad described above uses a grid of X and Y electrodes 12, 14 and a separate and single sense electrode 16, the sense electrode can actually be the X or Y electrodes 12, 14 by using multiplexing.
In a preferred embodiment, the present invention is a system and method for detecting the presence of a probe on or near an electrode that may transmit secure data by detecting a change in capacitance on the electrode, and wherein action may be taken to stop transmission on the electrode if a probe is detected.
These and other objects, features, advantages and alternative aspects of the present invention will become apparent to those skilled in the art from a consideration of the following detailed description taken in combination with the accompanying drawings.
Reference will now be made to the drawings in which the various elements of the present invention will be given numerical designations and in which the invention will be discussed so as to enable one skilled in the art to make and use the invention. It is to be understood that the following description is only exemplary of the principles of the present invention, and should not be viewed as narrowing the claims which follow.
It should be understood that use of the term “touch sensor” throughout this document includes any capacitive touch sensor device, including touchpads, touch screens and touch panels, and includes proximity and touch sensing capabilities.
Previous technology for securing a touch sensor is directed to the concept of protecting an operating volume. An operating volume may be defined as a space within which a touch sensor and its components such as touch sensing circuitry are disposed. Thus, an operating volume may be a housing of a point-of-sale (POS) terminal. A touch sensor and its touch sensing circuitry may be disposed within the POS terminal. Electrodes may be disposed around the inside of the POS terminal in order to sense the volume within the POS terminal. If there are changes that are detectable by capacitance sensitive circuitry within the POS terminal, then the detectable changes may cause a system to react to the changes. For example, the system may be able to prevent the interception of data when a probe is penetrating the POS terminal in order to insert an electrode for intercepting communication. The communication may be between the touch sensor and any other circuitry with which the touch sensor communicates.
The present invention may be directed to the concept of providing increased security for digital communications by focusing detecting efforts on individual communication lines. These communication lines may belong to any component, and not just to the touch sensor. The present invention may be directed to detection of a probe that is in proximity of or making direct contact with an electrode that functions as a communication line, wherein the probe may attempt to intercept signals on the electrode that is carrying information. The electrode may transmit data between two integrated circuits. The integrated circuits may provide any function. The electrode should not be considered as limited between two integrated circuits, and may carry any analog or digital signals.
A first embodiment of the present invention may be directed to the detection of a probe that is approaching any electrode that provides communication of data. It may be assumed that the probe may cause a change in capacitance on the electrode. The change in capacitance may be caused by proximity of the probe to the electrode or by direct contact on the electrode by the probe.
The touch sensor circuit 36 may be dedicated to the function of security as in the first embodiment, or it may also function in association with a touch sensor (not shown) so as to also perform touch sensor functions. The touch sensor circuit 36 may be capable of detecting changes in capacitance on the order of femtofarads or smaller.
After probe detection, the system of the first embodiment may take one of several different actions. These actions may be directed by the touch sensor circuit 36 or some other component that includes a microprocessor or a state machine. For this example, it may be assumed that the touch sensor circuit 36 includes some processing capabilities and is directing the actions to be performed if the probe 40 is detected.
First, the touch sensor circuit 36 may be capable of transmitting a signal to alert or warn another device or component of the presence of the probe 40. Second, the touch sensor circuit 36 may be capable of terminating the transmission of data on the plurality of electrodes 30 to thereby prevent interception of data. Third, the touch sensor circuit 36 may transmit a signal to another device that stops transmission of the data on the plurality of electrodes 30. What is important is that the transmission of data be terminated so that no more data may be intercepted.
The present invention may be capable of detecting the presence of the probe 40 on or near a single electrode that may transmit data, or on a plurality of different electrodes.
One application of the present invention may be in a financial transaction. A user may be required to enter a personal identification number (PIN) on a touch screen of a POS terminal. The PIN data may have to be transmitted from the touch screen in order to confirm the PIN data. The touch screen may include a touch sensor circuit that may be required to transmit the data to another component within the POS terminal in order to verify PIN data. Payment industry standards require protecting PIN data from being accessible by a probe that may try to capture signals from the touch screen. In some cases the integrated circuits and electrodes for connecting a touch controller IC (touch sensor circuit) and microprocessor are housed in a Tamper Resistant Security Module. However, the present invention now provides an additional layer of security. It should be understood that the data electrode that may be monitored may carry unsecure data or secure data.
The present invention may now monitor electrodes transmitting digital communication signals by periodically measuring current paths including the dielectric between the electrodes being protected and other nearby electrodes that may be strategically placed to sense changes in material such as etching, chipping or adding conductive inks, etc. The present invention may be used to detect any leakage of current or change in bulk capacitance of the protected electrodes.
The present invention may also be used to monitor other traces not necessarily associated with the touch IC communications such as to protect contact card connector and electrodes from probing or insertion of a man-in-the-middle device left in the contact card socket.
For example, the monitoring electrode may be disposed between two or more data electrodes to be monitored. There may also be a plurality of monitoring electrodes that are disposed in electrical proximity to a plurality of different data electrodes to be monitored.
The next step in item 52 is to make a capacitance measurement such as bulk capacitance of the data electrodes and capacitance between the data electrodes and other nearby data electrodes. This baseline measurement or measurements may be for a single monitoring electrode or for a plurality of monitoring electrodes that are in contact with or in electrical proximity of the data electrodes.
Once the baseline measurements have been made, the next step in item 54 is to record the baseline measurement or measurements that were made in the previous step. It is necessary to record the baseline measurements so that whenever new measurements are made, they may be compared with the baseline measurements that are stored somewhere in memory, such as in the touch sensor circuit 36.
The next step in item 56 is to continuously take new measurements and compare them with the baseline measurements that have been recorded. These new measurements may be made with either end of the data electrodes by driving high, driving low or being tri-stated, etc., as understood by those skilled in the art.
The final step is to take some action if a new measurement is different enough from a recorded baseline measurement. The decision to take action may be based upon a threshold value in the measured change in capacitance between the at least one monitoring electrode and the at least one data electrode. The specific threshold value for determining that action may be taken may be programmable and changeable.
It is to be understood that the above-described arrangements are only illustrative of the application of the principles of the present invention. Numerous modifications and alternative arrangements may be devised by those skilled in the art without departing from the spirit and scope of the present invention. The appended claims are intended to cover such modifications and arrangements.
| Number | Date | Country | |
|---|---|---|---|
| 61770181 | Feb 2013 | US |
