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.