Device security with physically unclonable functions

An electronic device, comprising:

• processing circuitry configured to perform at least one secure operation based on first physically unclonable function (PUF) data;
• and
• a PUF source comprising PUF circuitry and at least one circuit comprising a plurality of multiplexers, the at least one circuit having a plurality of signal paths passing through the plurality of multiplexers, the PUF circuitry configured to compare delays of the plurality of signal paths and to generate the first PUF data based on comparison of the delays, wherein the delays vary based on variation in a physical structure of the at least one circuit, and wherein the plurality of multiplexers include at least:
• a first multiplexer having an input for receiving a first signal transition;
• a second multiplexer having an input for receiving a second signal transition;
• a third multiplexer having an input for receiving an output of the first multiplexer and an input for receiving an output of the second multiplexer;
• and
• a fourth multiplexer having an input for receiving the output of the first multiplexer and an input for receiving the output of the second multiplexer.

A method for use with a payment reader device, comprising:

• receiving payment information at the payment reader device from a payment card;
• processing the payment information with the payment reader device;
• transmitting the processed payment information from the payment reader device to a payment server for approval of a payment transaction based on the processed payment information;
• storing, in memory of the payment reader device, a set of bits in a default state upon startup of the memory, wherein values of the bits in the default state define a pattern based on a physical structure of the memory;
• generating physically unclonable function (PUF) data based on the set of bits with PUF circuitry of the payment reader device;
• triggering a return of the bits to the default state upon startup of the memory in response to application of an operational voltage to the memory, wherein the generating comprises defining the PUF data based on the values exhibited by the bits in the default state;
• and
• performing, with the payment reader device, at least one secure payment operation for the payment transaction based on the PUF data.

A method for use with an electronic device, comprising:

• performing at least one secure operation with the electronic device based on physically unclonable function (PUF) data;
• comparing, with PUF circuitry of the electronic device, frequencies of a plurality of oscillator circuits of the electronic device;
• and
• generating the PUF data with the PUF circuitry based on the comparing, wherein the frequencies vary based on variation in a physical structure of the plurality of oscillator circuits.

A method for use with an electronic device, comprising:

• performing at least one secure operation with the electronic device based on physically unclonable function (PUF) data;
• comparing, with PUF circuitry of the electronic device, delays of a plurality of signal paths passing through a plurality of multiplexers of at least one circuit of the electronic device;
• generating the PUF data with the PUF circuitry based on the comparing, wherein the delays vary based on variation in a physical structure of the at least one circuit;
• receiving a first signal transition with a first multiplexer of the plurality of multiplexers;
• receiving a second signal transition with a second multiplexer of the plurality of multiplexers;
• receiving an output of the first multiplexer with a third multiplexer of the plurality of multiplexers;
• receiving an output of the second multiplexer with the third multiplexer;
• and
• receiving the output of the first multiplexer with a fourth multiplexer of the plurality of multiplexers;
• and
• receiving the output of the second multiplexer with the fourth multiplexer.