Rotating magnetic measurements of physical unclonable functions

1. A system comprising:

a body;

a substrate mounted to the body, configured to rotate about a first axis, and containing a plurality of magnetic particles; and

a non-volatile memory device mounted to the body and containing first field data corresponding to a first magnetic field generated by the magnetic particles, the first magnetic field is located along a first circular path centered on the first axis.

2. The system of claim 1 , wherein the substrate is a gear.

3. The system of claim 1 , wherein the substrate is a cylinder.

4. The system of claim 1 , wherein the first field data corresponds to 360 degrees around the first circular path.

5. The system of claim 1 , wherein the first field data corresponds to more than 360 degrees around the first circular path.

6. The system of claim 1 , wherein the memory device contains second field data corresponding to a second magnetic field generated by the magnetic particles, the second magnetic field is located along a second circular path centered on the axis, the second circular path encloses the first circular path.

7. The system of claim 1 , wherein the first field data contains information on the first magnetic field in at least two orthogonal directions.

8. The system of claim 1 , further comprising a coupling coupled to the body, the coupling is coupled to the substrate such that rotation of the coupling causes the substrate to rotate about the first axis.

9. The system of claim 1 , wherein the substrate is transparent.

10. The system of claim 9 , wherein the memory device contains first image data of the magnetic particles as viewed from the first circular path.

11. The system of claim 10 , wherein the first field data comprises a series of field data elements corresponding to a first sequential series of locations along the first circular path stored sequentially in the memory device starting with a first field data element, the first image data comprises a series of image data elements corresponding to a second sequential series of locations along the first circular path stored sequentially in the memory device starting with a first image data element, and an absolute value of a central angle of the first circular path between the location corresponding to the first field data element and the location corresponding to the first image data element is greater than 45 degrees.

12. The system of claim 11 , wherein the central angle is 180 degrees.

13. The system of claim 1 , wherein the memory device contains second image data of the magnetic particles as viewed from a third circular path centered on the first axis, the third circular path encloses the first circular path.

14. The system of claim 1 , wherein the memory device contains first polarization data of the substrate as viewed from the first circular path.

15. The system of claim 1 , wherein the first circular path is located adjacent to the substrate.

16. The system of claim 1 , wherein the substrate is mounted to the body via a shaft defining the first axis, the substrate has a side opposite the body, and the shaft protrudes beyond the substrate on the side opposite the body.

17. The system of claim 1 , wherein the substrate has a raised collar around the axis located within the first circular path.

18. A system comprising:

a body;

a substrate mounted to the body, configured to rotate about an axis, and containing a plurality of magnetic particles dispersed in the substrate;

a raised collar located around the axis having an outer surface; and

a non-volatile memory device mounted to the body containing first field data corresponding to a magnetic field generated by the magnetic particles, the field is located along a first path that encloses the axis, the first path follows the outer surface at a fixed offset.

19. A method of manufacturing an authentication device comprising:

attaching a non-volatile memory device to a body;

attaching a substrate to the body, the substrate is configured to rotate about an axis and contains a plurality of magnetic particles;

generating first magnetic field data by measuring along a first circular path centered on the first axis a first magnetic field generated by the magnetic particles;

encrypting the first magnetic field data; and

writing the encrypted first magnetic field data to the non-volatile memory device.

20. The method of claim 19 , wherein the first magnetic field data corresponds to more than 360 degrees around the first circular path.

21. The method of claim 19 , further comprising:

generating second magnetic field data by measuring along a second circular path centered on the first axis a second magnetic field generated by the magnetic particles, the second circular path encloses the first circular path;

encrypting the second magnetic field data; and

writing the encrypted second magnetic field data to the non-volatile memory device.

22. The method of claim 19 , wherein the first magnetic field data contains information on the first magnetic field in at least two orthogonal directions.

23. The method of claim 19 , further comprising:

generating first image data of the magnetic particles as viewed along the first circular path;

encrypting the first image data; and

writing the encrypted first image data to the memory device.

24. The method of claim 23 , wherein the first magnetic field data comprises a series of field data elements corresponding to a first sequential series of locations along the first circular path starting with a first field data element, the first image data comprises a series of image data elements corresponding to a second sequential series of locations along the first circular path starting with a first image data element, and an absolute value of a central angle of the first circular path between the location corresponding to the first field data element and the location corresponding to the first image data element is greater than 45 degrees.

25. The method of claim 24 , wherein the central angle is 180 degrees.

26. The method of claim 19 , further comprising:

generating first polarization data of the substrate as viewed along the first circular path;

encrypting the first polarization data; and

writing the encrypted first polarization data to the memory device.