Measure variation tolerant physical unclonable function device

Abstract

This application discloses a physical unclonable function device including physical unclonable function units, each capable of generating an output. The physical unclonable function device can extract bits from the outputs at various inspection locations and utilize the extracted bits to generate an identifier for the physical unclonable function device. An inspection configuration tool can identify the inspection locations and configure the physical unclonable function device with the inspection locations. The inspection configuration tool can sample the physical unclonable function circuitry to identify a plurality of multi-bit outputs, select bit locations in the multi-bit outputs as inspection locations based on bit value stability for the bit locations, and configure the identifier generation circuitry in physical unclonable function device with the inspection locations.

1 . A method comprising:
 sampling a physical unclonable function unit in a physical unclonable function device to identify a plurality of multi-bit outputs;   analyzing bit value stability for one or more bit locations across the multi-bit outputs to select a bit location in the multi-bit outputs as an inspection location; and   configuring the physical unclonable function device with the inspection location, wherein the physical unclonable function device is configured to generate an identifier based, at least in part, on a bit value corresponding to the bit location selected as the inspection location for the physical unclonable function unit.   
     
     
         2 . The method of  claim 1 , further comprising determining the bit value stability for the one or more bit locations in the multi-bit outputs, wherein analyzing bit value stability for one or more bit locations further comprises comparing the bit value stability for the one or more bit locations to a predetermined stability threshold and selecting the bit location as the inspection bit based on the comparison. 
     
     
         3 . The method of  claim 2 , wherein analyzing bit value stability for one or more bit locations further comprises scanning the bit locations, starting with a most significant bit location and moving towards a least significant bit location, to identify a bit location that fails to exceed the predetermined stability threshold, and wherein the bit location selected as the inspection location corresponds to a bit location scanned prior to identifying the bit location that fails to exceed the predetermined stability threshold. 
     
     
         4 . The method of  claim 2 , wherein analyzing bit value stability for one or more bit locations further comprises scanning the bit locations, starting with a least significant bit location and moving towards a most significant bit location, to identify a bit location that exceeds the predetermined stability threshold, and wherein the bit location selected as the inspection location corresponds to the bit location that exceeds the predetermined stability threshold. 
     
     
         5 . The method of  claim 1 , wherein the physical unclonable function device includes one or more components having physical characteristics that randomly fall within a tolerance range during manufacture, and wherein the physical unclonable function device is configured to generate the multi-bit outputs with values based, at least in part, on the physical characteristics of the one or more components. 
     
     
         6 . The method of  claim 1 , wherein configuring the physical unclonable function device with the inspection location further comprises modifying a design of the physical unclonable function device to utilize the inspection location to generate the identifier. 
     
     
         7 . The method of  claim 6 , wherein the modifying the design of the physical unclonable function device further comprises altering a size of a counter in the physical unclonable function device so that the inspection location corresponds to a most significant bit of the counter. 
     
     
         8 . A device comprising:
 physical unclonable function circuitry configured to generate a plurality of outputs; and   identifier generation circuitry configured to extract a bit from each of the outputs based, at least in part, on bit value stability for bit locations in the outputs, wherein the identifier generation circuitry is configured to generate an identifier with the bits extracted from the outputs at the bit locations.   
     
     
         9 . The device of  claim 8 , wherein the physical unclonable function circuitry includes multiple physical unclonable function units, each including one or more components having physical characteristics that randomly fall within a tolerance range during manufacture 
     
     
         10 . The device of  claim 9 , wherein each of the physical unclonable function units is configured to generate a corresponding one of the outputs based, at least in part, on the physical characteristics of the one or more components. 
     
     
         11 . The device of  claim 9 , wherein the identifier generation circuitry is configured to sample multiple outputs from one of the physical unclonable function units, analyze one or more of the bit locations in the sampled multi-bit outputs to determine bit value stability for the one or more bit locations in the multiple outputs, and select one of the bit locations to utilize as an inspection location for the physical unclonable function unit. 
     
     
         12 . The device of  claim 11 , wherein the identifier generation circuitry is configured to extract a bit from the bit location in the output corresponding to the inspection location. 
     
     
         13 . The device of  claim 11 , wherein the identifier generation circuitry is configured to compare the bit value stability for the one or more bit locations in multiple outputs to a predetermine stability threshold, and select the bit location as the inspection bit based on the comparison. 
     
     
         14 . An apparatus comprising at least one computer-readable memory device storing instructions configured to cause one or more processing devices to perform operations comprising:
 determining bit value stability for one or more bit locations across multi-bit outputs from a physical unclonable function unit in a physical unclonable function device;   selecting a bit location in the multi-bit outputs as an inspection location based on the bit value stability for the one or more bit locations; and   configuring the physical unclonable function device with the inspection location, wherein the physical unclonable function device is configured to generate an identifier based, at least in part, on a bit value corresponding to the bit location selected as the inspection location for the physical unclonable function unit.   
     
     
         15 . The system of  claim 14 , wherein the instructions are further configured to cause the one or more processing devices to perform operations comprising scanning the bit locations, starting with a most significant bit location and moving towards a least significant bit location, to identify a bit location that fails to exceed the predetermined stability threshold, wherein the bit location selected as the inspection location corresponds to a bit location scanned prior to identifying the bit location that fails to exceed the predetermined stability threshold. 
     
     
         16 . The system of  claim 14 , wherein the instructions are further configured to cause the one or more processing devices to perform operations comprising scanning the bit locations, starting with a least significant bit location and moving towards a most significant bit location, to identify a bit location that exceeds the predetermined stability threshold, wherein the bit location selected as the inspection location corresponds to the bit location that exceeds the predetermined stability threshold. 
     
     
         17 . The system of  claim 14 , wherein the physical unclonable function device includes one or more components having physical characteristics that randomly fall within a tolerance range during manufacture. 
     
     
         18 . The system of  claim 17 , wherein the physical unclonable function device is configured to generate the multi-bit outputs with values based, at least in part, on the physical characteristics of the one or more components. 
     
     
         19 . The system of  claim 14 , wherein configuring the physical unclonable function device with the inspection location further comprises modifying a design of the physical unclonable function device to utilize the inspection location to generate the identifier from the future multi-bit output. 
     
     
         20 . The system of  claim 19 , wherein the modifying the design of the physical unclonable function device further comprises altering a size of a counter in the physical unclonable function device so that the inspection location corresponds to a most significant bit of the counter.