Methods of Making Physical Unclonable Functions Having Magnetic Particles

Abstract

A method of making a physical unclonable function (PUF) having magnetic and non-magnetic particles is disclosed. Measuring both magnetic field and image view makes the PUF difficult to counterfeit. PUF may be incorporated into a user-replaceable supply item for an imaging device. A PUF reader may be incorporated into an imaging device to read the PUF. Other methods are disclosed.

What is claimed is: 
     
         1 . A method of making a security device comprising:
 mixing a substrate material and a plurality of magnetizable particles;   causing the substrate material and magnetizable particles to become solid as aggregate pellets;   magnetizing the magnetizable particles in the aggregate pellets so that a magnetic field orientation of the magnetized particles will be random; and   forming the aggregate pellets into the security device.   
     
     
         2 . The method of  claim 1 , wherein the magnetizable particles are flakes having an average thickness that is less than their average diameter. 
     
     
         3 . The method of  claim 1 , wherein the magnetizable particles contain neodymium and iron and boron. 
     
     
         4 . The method of  claim 1 , wherein the magnetizable particles contain samarium and cobalt. 
     
     
         5 . The method of  claim 1 , wherein the magnetizable particles are flakes having an average thickness that is less than an average diameter of the flakes. 
     
     
         6 . The method of  claim 1 , wherein the magnetizable particles have an average diameter of between 50 and 500 microns inclusive. 
     
     
         7 . The method of  claim 1 , wherein the magnetizable particles contain neodymium and iron and boron. 
     
     
         8 . The method of  claim 1 , wherein the magnetizable particles contain samarium and cobalt.