Patent ID: 9444618
Filing Date: 2016-09-13
CPC Classification: H04L

Claim Text:
1. A circuit, comprising: a ring oscillator-based physically unclonable function (PUF); a control circuit coupled to the ring oscillator-based PUF; a non-volatile memory coupled to the control circuit and configured with a plurality of frequency-versus-time profiles, each frequency-versus-time profile associated with a different operating temperature; and wherein the control circuit is configured to monitor operating conditions of the ring oscillator-based PUF, disable the ring oscillator-based PUF in response to the operating conditions being out-of-tolerance, and enable the ring oscillator-based PUF in response to the operating conditions being in-tolerance; wherein the control circuit includes: a frequency monitor coupled to the temperature sensor and configured and arranged to sample frequencies of a ring oscillator of the ring oscillator-based PUF over a sample period when the temperature is measured, generate a measured frequency-versus-time profile based on the sampled frequencies, and compare the measured frequency-versus-time profile to one of the plurality of frequency-versus-time profiles corresponding to the measured temperature to determine whether or not the sampled frequencies are within an acceptable range for the temperature and detect out-of-tolerance operation of the ring oscillator-based PUF; wherein the control circuit is further configured to: