Mitigating side channel attacks
AssigneeNordic Semiconductor ASA
InventorFrode Pedersen
Life of this patent
Estimating the term…
Abstract
An integrated circuit includes a closed loop oscillator circuit portion. The closed loop oscillator circuit portion has an input for a reference clock signal and an output providing an output clock signal to one or more further components of the integrated circuit. The output clock signal has an average output frequency derived from the reference clock signal. The closed loop oscillator circuit portion is operable in a spread spectrum mode in which the closed loop oscillator circuit portion varies a frequency of said output clock signal, by temporarily increasing the frequency by a predetermined amount and temporarily decreasing the frequency by said predetermined amount, at different times, within a predetermined multiple of a clock cycle of the reference clock signal.
Claims14
An integrated circuit comprising:
- a closed loop oscillator circuit portion comprising:
- an input for a reference clock signal;
- an output providing an output clock signal to one or more further components of the integrated circuit, the output clock signal having an average output frequency derived from the reference clock signal;
- wherein the closed loop oscillator circuit portion is arranged to be operable in a spread spectrum mode in which the closed loop oscillator circuit portion varies a frequency of said output clock signal, by:
- increasing the frequency of the output clock signal to a first constant frequency equal to the average output frequency increased by a predetermined offset frequency amount for a first frequency shift period;
- followed by:
- decreasing the frequency of the output clock signal to a second constant frequency equal to the average output frequency decreased by said predetermined offset frequency amount for a second frequency shift period;
- wherein the first and second frequency shift periods are a predetermined multiple of the clock cycle of the reference clock signal.
A method of operating an integrated circuit, the integrated circuit comprising a closed loop oscillator circuit portion, comprising the oscillator circuit portion:
- receiving a reference clock signal;
- generating an output clock signal having an average output frequency derived from the reference clock signal, providing said output clock signal to one or more further components of the integrated circuit;
- and the method comprising, in a spread spectrum mode:
- the oscillator circuit portion varying a frequency of said output clock signal, by:
- increasing the frequency of the output clock signal to a first constant frequency equal to the average output frequency increased by a predetermined offset frequency amount for a first frequency shift period;
- followed by:
- decreasing the frequency of the output clock signal to a second constant frequency equal to the average output frequency decreased by said predetermined offset frequency amount for a second frequency shift period;
- wherein the first and second frequency shift periods are a predetermined multiple of the clock cycle of the reference clock signal.
Dependencies are inferred from the claim text.