Fabricated Printed Circuit Boards (PCBs) for Identification, Authentication,
and Cryptographic Key Derivation
Many electronic systems use security systems with digital identification for authentication and key derivation. One system security method uses an optical physical unclonable function (PUF), implemented on a printed circuit board. PUFs are constructed from light emitting diodes (LEDs) and an image sensor affixed to the PCB, which is then coated with a thin polymer planar waveguide. The system is designed to create a unique key value from the sensor image. Invasive attempts damage the polymer coating, thus destroying the PUF value. Current methods of fabricating the waveguide reflectors rely on silver reflectors. These reflectors demonstrate large light loss at critical reflection angles and require special processing methods or manufacturing, dramatically increasing production costs.
The invention provides an alternative to the silver reflectors used in the polymer planar waveguide. Replacing the silver reflectors with dielectric reflectors resulted in the essentially total reflection of light in the critical reflection angles. Theoretical predictions indicate a more than doubled efficiency increase in light transportation. This would vastly increase the sharpness of the sensor image generated resulting in a stronger security system. The innovation also exhibits a large degree of flexibility as the dielectric material can be chosen for the particular application of interest. In addition, the dielectric reflectors do not require special processing methods for fabrication, vastly diminishing the cost of production.
transportation to sensor increased by factor of 2 over conventional waveguides
design allows for application-specific choice of dielectric material
fabrication due to no special processing requirements