Physically Unclonable Functions for Fully Fabricated Printed Circuit Boards used in Identification, Authentication, and Cryptographic Key Derivation


  • Electronic systems needing to incorporate unclonable identification devices for authentication and cryptographic key derivation

Problem Addressed

Many electronic systems use digital identification for authentication and key derivation to achieve system security. 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. However, there is a concern that advanced invasive methods can deduce the original PUF value from a damaged sensor image.


The invention provides a method for manufacturing a waveguide which increases the image distortion between the original and damaged image. This significantly increases the difficulty in deducing the initial PUF value from a damaged image. The technology employs a novel two-color phosphor-loaded waveguide technology. When an invasive attempt is made on the system, not only is the image distorted, but color sensitive phosphor is also activated causing a color change in the system. The device can be applied to systems after full fabrication, allowing the security systems of manufactured electronics to be upgraded.  


  • Includes optical effects for improved security and hacker detection
  • Increases image distortion for heightened protection of PUF value from hackers
  • Applicable to fully fabricated systems needing security system upgrades