Secured pin entry device
View Patent ↗The invention is a keypad for securely entering personal identification numbers onto automated teller machines (ATM) or similar devices. A frame secures a flexible keypad to a printed circuit board. The front of the circuit includes a set of tamper detection contacts whose electrical circuit is completed by conductive material on the keypad surface. A moat of conductive material surrounds the tamper detection contact. Opening the circuit by removing the keypad or shorting the circuit to the moat initiates a tamper response. Attached to the reverse side of the printed circuit board are security sensitive electrical components. These security sensitive components include a static random access memory storing cryptographic information and a crypto processor. A plastic cover imprinted with a tamper detection grid forming multiple electrical circuits coupled to a tamper detection circuit covers these components. A border of conductive material on the printed circuit board also surrounds these components. Opening or shorting any of the circuits in the grid initiates a tamper response, and shorting any of the components to the border also initiates a tamper response.
1. A tamper detection circuit for a secured key-based entry device for a computer system comprising:
a keypad having a plurality of keycaps that initiate one or more electronic signals when depressed, the signals are used in a computer system;
a frame securing the keypad to the entry device;
a circuit board having electrical contacts that are coupled to a portion of one or more keycaps on the keypad when the keycaps are depressed, the one or more electronic signals are initiated by one or more electrical components on the circuit board based on the particular keycap being depressed;
a tamper detection contact on the circuit board comprising a first conductive pattern and a second conductive pattern, the tamper detection contact initiating a signal when the first and the second conductive patterns are not connected by an electrical switch applied between the first and second patterns;
a third conductive pattern surrounding a predetermined area around the first and second conductive patterns, the third conductive pattern coupled to a predetermined voltage level; and
a non-conductive moat separating the third conductive pattern and either the first or the second conductive patterns, the non-conductive moat initiating a tamper detection response protocol by a transmission of electrical signals between the third conductive pattern and either the first or second conductive pattern.
2. A secured key-based entry device according to claim 1 , further comprising:
a cover for the electrical components having a tamper detection grid coupled to the tamper detection circuit; and
a surrounding layer of conductive trace material on the circuit board bordering the electrical components.
3. A secured key-based entry device according to claim 2 , further comprising a tamper response-protocol initiated when tampering is detected by fluctuations in the electric signals from the tamper detection circuit coupled to the tamper detection grid.
4. A secured key-based entry device according to claim 1 , wherein the electrical switch between the first and second patterns includes electrical conductive material on a keypad.
5. A secured key-based entry device according to claim 1 , wherein the tamper response protocol renders the device inoperable.
6. A secured key-based entry device for a computer system comprising:
a keypad having a plurality of keycaps that initiate one or more electronic signals when depressed;
a frame securing the keypad to the entry device; and
a circuit board having electrical contacts that are coupled to a portion of one or more keycaps on the keypad when the keycaps are depressed, the one or more electronic signals being initiated by one or more electrical components on the circuit board based on the particular keycap being depressed, the circuit board comprising a tamper detection contact which includes a first conductive trace, a second conductive trace which is electrically isolated from the first conductive trace, and a third conductive trace which is electrically isolated from the first and second conductive traces, wherein a tamper response protocol is initiated to either render the device inoperable or erase stored cryptographic information, or both, when the third conductive trace electrically shorts to either the first conductive trace or the second conductive trace.
7. A secured key-based entry device according to claim 6 , wherein the electrical components include a static random access memory storing encryption keys.
8. A secured key-based entry device according to claim 7 , wherein the electrical components include a crypto processor.