TAMPER RESISTANT ELECTRONIC TRANSACTION ASSEMBLY

1 . A tamper resistant user interface device comprising:

a substantially planar sensor, said sensor comprising a plurality of user activated membrane switches; and

at least one multilayer structure folded around and overlaying said planar sensor, said structure comprising at least one layer to detect tampering with said sensor.

2 . The device of claim 1 , wherein said sensor is in the form of a keyboard or a keypad.

3 . The device of claim 1 , wherein said multilayer structure further comprises a plurality of serpentine conductor layers.

4 . The device of claim 1 , wherein said plurality of membrane switches comprises a circuit printed on a thermoplastic polymer resin.

5 . The device of claim 1 , wherein said multilayer structure further comprises a drill plate, said drill plate comprising a film, said film coated on both sides with silver conductive ink, wherein when said film is penetrated, an electrical short is created between said silver conductive ink on both sides.

6 . The device of claim 5 , wherein said film comprises a polyvinylidene difluoride (PVDF) film.

7 . The device of claim 1 , wherein said multilayer structure further comprises a breakwire pattern, said pattern comprising:

a film; and

a plurality of narrow conductors printed on said film,

wherein said breakwire pattern is adapted to receive a small electrical current, which current will be interrupted if said breakwire pattern is broken.

8 . The device of claim 7 , wherein said film comprises a polyvinylidene difluoride (PVDF) film.

9 . The device of claim 1 , wherein said multilayer structure comprises:

a first outer liner layer;

a first thin layer of pressure sensitive adhesive layer adjacent to said first outer liner layer;

a first electrical insulation layer adjacent to said first thin layer of pressure sensitive adhesive layer;

a first PVDF film;

a first conductive ink layer interposed between said first electrical insulation layer and said first PVDF film;

a second adhesive layer adjacent to said first PVDF film;

a second PVDF film;

second and third layers of conductive ink layers disposed on either side of said second PVDF film;

a third adhesive layer;

a third PVDF film;

a second electrical insulation layer;

a fourth conductive ink layer interposed said third PVDF layer and said second electrical insulation layer;

a fourth pressure sensitive adhesive layer adjacent to said second electrical insulation layer; and

a second outer liner layer adjacent to said fourth pressure sensitive adhesive layer.

10 . The device of claim 2 , wherein said keyboard or keypad is disposed in an electronic transaction machine.

11 . An electronic transaction assembly comprising a circuit for detecting tampering with a user interface containing a sensor, said circuit comprising:

first and second drill layers on either side of a substantially planar sensor;

first and second electrical leads electrically coupled to said first and second drill layers respectively;

first and second serpentine conductive layers adjacent to said first and second drill layers respectively;

third and fourth electrical leads electrically coupled across said first and second serpentine conductive layers respectively; and

a fifth electrical lead coupled between said first and second conductive layers;

wherein, peel-type tampering is detected by checking continuity between said third and fifth leads and between said fourth and fifth leads and penetration-type tampering is detected by checking for shorts between said first and second leads connected to said first and second drill layers respectively.

12 . The assembly of claim 11 , further comprising an indicator, said indicator adapted to provide an indication of tampering responsive to signals sensed using said first, second, third, fourth and fifth leads.

13 . The assembly of claim 12 , wherein said indicator provides an audible indication.

14 . The assembly of claim 12 , wherein said indicator provides a visual indication.

15 . The assembly of claim 11 , wherein said circuit is selectively disabled responsively to signals sensed using said first, second, third, fourth, and fifth leads.

16 . The assembly of claim 11 , wherein said assembly is a point of sale card reader.

17 . A method for detecting tampering with a sensor, said method comprising the steps of:

checking for electrical shorts between first and second electrical leads coupled to first and second drill layers disposed on either side of a substantially planar sensor of a keyboard or keypad of an electronic transaction machine; and

checking for a break in continuity between third and fourth electrical leads, and between fifth and fourth electrical leads, wherein said third and fifth electrical leads are electrically coupled across first and second conductive layers adjacent to said first and second drill layers respectively and said fourth electrical lead is coupled between said first and second conductive layers.

18 . The method of claim 17 , further comprising providing a visual or audible indicator in response to detection of said electrical short or said break in continuity.

19 . The method of claim 17 , further comprising disabling said electronic transaction machine in response to detection of said electrical short or said break in continuity.