Physical unclonable function configuration and readout

A Physical Unclonable Function, PUF, system comprising:

• a pair of devices for use in generating a persistent random value;
• and
• a determination unit for configuring the pair of devices, the determination unit being arranged to:
• measure a physical characteristic of the pair of devices, wherein the measurement of the physical characteristic is indicative of a random manufacturing variation between the pair of devices;
• compare the measurement of the physical characteristic against one or more configuration thresholds;
• and
• set, based on the comparison, a configuration indicator associated with the pair of devices to assign the pair of devices to either:
• a first readout condition;
• or
• a second readout condition;
• wherein the first read-out condition indicates that when generating the persistent random value using the pair of devices during PUF readout, the physical characteristic of the pair of devices should be compared against at least one first readout condition threshold.

A method of reading out a Physical Unclonable Function, PUF, system that comprises a pair of devices, the method comprising:

• reading a configuration indicator associated with the pair of devices to determine if the pair of devices was assigned during configuration to a first read-out condition or to a second readout condition;
• and
• if the configuration indicator is indicative of the pair of devices being assigned to the first readout condition:
• determining a persistent random value using the pair of devices by comparing a physical characteristic of the pair of devices against at least one first readout condition threshold, wherein the physical characteristic is indicative of a random manufacturing variation between the pair of devices;
• otherwise
• if the configuration indicator is indicative of the pair of devices being assigned to the second readout condition:
• performing a second readout condition action.

A Physical Unclonable Function, PUF, system comprising:

• a pair of devices for use in generating a persistent random value;
• and
• a determination unit configured to:
• read a configuration indicator associated with the pair of devices to determine if the pair of devices was assigned during configuration to a first read-out condition or to a second readout condition;
• and
• if the configuration indicator is indicative of the pair of devices being assigned to the first readout condition:
• determine a persistent random value using the pair of devices by comparing a physical characteristic of the pair of devices against at least one first readout condition threshold, wherein the physical characteristic is indicative of a random manufacturing variation between the pair of devices;
• otherwise
• if the configuration indicator is indicative of the pair of devices being assigned to the second readout condition:
• perform a second readout condition action.