Physical Unclonable Function Variable Read Sensor

Abstract

Magnetic PUFs (Physical Unclonable Function) may utilizes a single 3-axis Hall-effect sensor for enrollment. When a PUF is manufactured, a Hall-effect sensor is used to model the PUF disk and store that data where it may be accessed. This process is called “enrollment.” This invention improves upon the PUF implementation by introducing controlled variability into the enrollment, the reading of the PUF data from the Hall-effect sensors (the number and position of read sensors), the sampling method of the read sensor(s), and the processing of the PUF data.

We claim: 
     
         1 . A rotary encoder system within a device for tracking motor movements comprising:
 a closed-loop control algorithm on the motor system;   physical disk with magnetic particles dispersed in the disk substrate; and   one or more magnetic sensors that measure a magnetic field vector.   
     
     
         2 . The rotary encoder system of  claim 1 , wherein the device is a printer. 
     
     
         3 . The rotary encoder system of  claim 2 , wherein the system is used to control the amount of toner that is fed out of the cartridge based on the print or process speed. 
     
     
         4 . The rotary encoder system of  claim 1 , wherein the physical disk also has non-magnetic particles. 
     
     
         5 . The rotary encoder system of  claim 1 , wherein the magnetic particles are comprised of an alloy of neodymium, iron, and boron. 
     
     
         6 . The rotary encoder system of  claim 1 , wherein the magnetic particles are comprised of an alloy of samarium and cobalt. 
     
     
         7 . A rotary encoder system within a device for tracking motor movements comprising:
 a closed-loop control algorithm on the motor system;   physical disk with magnetic particles dispersed in the disk substrate;   one or more magnetic sensors offset that measure a magnetic field vector, wherein the sensors are offset in position such that they may act as a quadrature encoder to measure spin direction.   
     
     
         8 . A method of initializing and calibrating a PUF encoder to define the expected pattern of the field plot through one complete rotation comprising:
 a PUF magnetic sensor data collection is enabled;   an encoder disk motor is powered;   a time versus field strength plot is generated by rotating the encoder disk more than 360° during enrollment in order to confidently build a wrap point in the data;   while calibrating, field strength amplitude readings are interpolated so that a fixed time scale plot can be generated, from which the wrap point is selected;   the timestamped data is processed to identify a vector match for a first point, within a reasonable margin of error for sensor accuracy, thereafter, point is proposed as the wrap point element;   once a match for the first point is found, subsequent data points are also a vector match to the data points immediately following the proposed wrap point element;   the beginning and ending data point timestamps are compared to compute a calibration motor speed (revolutions per minute);   a sample resolution is calculated by counting the number of data points collected before data wrapping began and dividing by 360°;   the motor control parameters and magnetic sensor sample rate are adjusted, if necessary;   the data collection process is repeated until the desired operating speed and resolution are achieved.   
     
     
         9 . The method of claim  10 , wherein the field strength versus rotational position plot, a calibration plot, is stored for use in all future speed calculation and positional detection algorithms.