The use of a magnetic particle based “PUF” (Physically Unclonable Function) disk, when read by magnetic sensor(s), as a positional encoder is described. It is often necessary to include a linear or rotary encoder within a device for tracking motor movements, or to enable a closed-loop control algorithm on the motor system. These randomly dispersed magnetic particle disks can be used as a positional encoder, where the speed of movement and the direction of movement may be monitored.