Acoustical physically unclonable function (puf) and system
The present invention is a diverse acoustical object containing a range of particles that have acoustical wave impedances that are substantially different from the binder. The particles create a substantially different reflection as an acoustic wave is scattered by the particles. A negative reflection is created when the scattered wave is from a particle that has a wave impedance that is substantially less than the binder impedance. Practically, it may be necessary to encase this material in a thin material that will withstand the fabrication process (e.g., air or silicone elastomer could be encased in glass). If the wavelength is large compared to the encasing material thickness, then the reflection will be more dependent on the interior material. A mixture of materials that generate positive as well as negative reflections within the binder would add to the complexity of the PUF.
1. An acoustic Physically Unclonable Function (PUF) object with a predetermined acoustic profile comprising:
a binder material;
particles that have an acoustic impedance that is at least 50% different than the binder, wherein the particles respond differently to an acoustic wave.
2. The acoustic object of claim 1 , wherein the particle have a defined shape.
3. The acoustic object of claim 2 , wherein the particle shapes, including cuboid, parallelepiped, polyhedron, cylinder, ellipsoid, or other basic geometric shapes.
4. The acoustic object of claim 1 , wherein the particles have a size measured by the longest dimension of the particle.
5. The acoustic object of claim 4 , wherein the particle size is approximately two times the size of a sensor resolution inside the binder material.
6. The acoustic object of claim 1 , wherein the binder is nylon or polycarbonate.
7. The acoustic object of claim 6 , wherein the particle is glass, aluminum, tin, alumina, brass, iron, copper, nickel, or gold.
8. The acoustic object of claim 1 , wherein a loading defined as a fill ratio of a volume of the particles to a volume of binder is greater than 1% by volume.
9. The acoustic object of claim 8 , wherein the loading is greater than 10% by volume and less than 30% by volume.
10. The acoustic object of claim 9 , wherein the loading is approximately 20% by volume.
11. A method of making an acoustical Physically Unclonable Function (PUF) object comprising:
processing a reflective or an absorbing material into a particle form by grinding, cutting or pulverizing into a selected range of particle sizes;
mixing the particles with a binder, wherein the binder may also contain other particles with known acoustic properties to form a mixture;
heating the mixture to further combined the particles and binder in an extruder or similar equipment to form a matrix of particles and binder; and extruding the resulting matrix.
12. The method of claim 11 , wherein magnetic materials that can be magnetized creating a multi-characteristic PUF are added to the mixture.
13. The method of claim 11 , further comprising the step of extruding the matrix into an intermediate or final form.
14. The method of claim 13 , wherein a mold is used to create the intermediate or final form.