Differential uncloneable variability-based cryptography

A method for determining an output of a public physically uncloneable function , the method comprising:

• providing a first input to a first physically uncloneable circuit;
• providing the first input to a second physically uncloneable circuit at the same time;
• providing a first output of the first physically uncloneable circuit and a second output of the second physically uncloneable circuit to an arbiter, wherein the arbiter selects one of the first output and the second output as an output of the arbiter;
• providing a second input to both the first and second physically uncloneable circuit, wherein the second input changes the output of the arbiter;
• and
• clocking the output of the arbiter at a predetermined time to determine an output of the public physically uncloneable function.

A method for exchanging private information, the method comprising:

• receiving a simulated output from a simulating device having a public description of a public physically uncloneable function, wherein the simulated output is determined from an input selected from a range of inputs;
• receiving a time from the simulating device;
• searching, with the public physically uncloneable function, the range of inputs to find the input using the output and the time, wherein the public physically uncloneable function determines the output by arbitrating between a first physically uncloneable circuit and a second physically uncloneable circuit;
• finding the input when the output of the public physically uncloneable function at the time matches the simulated output;
• and
• determining the private information from the input of the public physically uncloneable function when the input is found.