Anti-counterfeiting label preserving functionality after use
A near field magnetically coupled anti-counterfeiting tag comprises a control microcircuit configured to implement a basic function and a cryptographic function; a sacrificial conductive track located across a sacrificial area of the tag; and a circuit for detecting continuity of the sacrificial track, cooperating with the microcircuit to implement the basic function without implementing the cryptographic function when the sacrificial track is broken.
1. A near field magnetically coupled contactless tag, comprising:
a control chip for implementing a basic function and a cryptographic function (CCP);
a sacrificial conductive track located across a sacrificial area of the tag; and
a circuit for detecting continuity of the sacrificial track, cooperating with the microcircuit to implement the basic function without implementing the cryptographic function when the sacrificial track is broken.
2. The tag according to claim 1 , wherein the microcircuit is a standard microcircuit comprising a programmable digital input/output pin (IO), the sacrificial track being connected between the input/output pin and a power supply pin (GND) of the microcircuit, the microcircuit being programmed to test the state of the input/output pin to determine the implementation of the cryptographic function.
3. The tag according to claim 1 , comprising an antenna circuit configured to ensure a continuity detection function, the sacrificial track being connected to the antenna circuit so that its rupture shifts the frequency tuning of the antenna circuit, the offset in the tuning frequency being selected such that the supply power received by the microcircuit is lowered to a level insufficient for implementing the cryptographic function, yet sufficient for implementing the basic function.
4. The tag according to claim 3 , comprising:
a foldable substrate in the form of a tape;
an antenna included in the antenna circuit;
a capacitor (C 1 ) connected to the antenna circuit;
a sacrificial impedance (C 1 s , C 2 s ); and
the sacrificial track configured on the tape to connect the sacrificial impedance (C 1 s , C 2 s ) to the antenna circuit.
5. The tag according to claim 4 , wherein:
the antenna comprises turns wound in a ring around a central area of the tape;
the sacrificial impedance (C 1 s ) is located at a first end of the tape; and
the sacrificial track includes a loop extending toward a second end of the tape.
6. The tag according to claim 5 , comprising a plurality of tapes intersecting at the antenna, the sacrificial track forming a loop in each tape segment extending from the antenna, except a segment supporting the sacrificial impedance (C 1 s ).
7. The tag according to claim 5 , comprising a plurality of tapes intersecting at the antenna, the sacrificial track forming a loop in a tape segment opposite to that supporting the sacrificial impedance (C 1 s ).
8. A container comprising:
a cork; and
a tag according to claim 5 wherein the substrate region carrying the antenna has a smaller diameter than the cork, fixed by glue to the container and cork so that the antenna is centered on the cork.
9. The container of claim 8 , wherein conductive tracks of the tag are located on the side of the tape facing the container, whereby an attempt to remove the tape damages the conductive tracks.
10. The container of claim 8 in the form of a bottle comprising a cap enveloping the cork, the neck of the bottle, and the tape, the cap including, in the vicinity of the cork, a material permeable to magnetic field.
11. The tag according to claim 4 , wherein the tape includes breaking points between the antenna and the sacrificial impedance.
12. The tag according to claim 4 , wherein the sacrificial track comprises two segments located on either side of the tape, and configured as a twisted pair.