PUF Cell Bias Switching for Stable Key Generation
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Solution Overview
Problem
Conventional physically unclonable function (PUF) devices are vulnerable to noise and environmental factors, leading to unstable key generation and high power consumption, with existing solutions requiring error correction circuits and significant chip area for masking to ensure stable operation.
Innovation Solution
A semiconductor device with a PUF cell array that combines threshold voltage difference and oscillation frequency difference amplification schemes, using bias voltages of different magnitudes to stabilize output values and reduce noise sensitivity, while minimizing power consumption and masking cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage amplifiers are used to amplify threshold voltage difference, then key generation is achieved, but the device becomes weak against noise and requires error correction circuits that increase power consumption
Solution Approach 1:
The patent replaces the voltage amplifier-based PUF with an oscillator-based PUF that uses frequency difference. This substitution eliminates the need for error correction circuits and masking cells, thereby reducing power consumption while maintaining key generation stability. The oscillator structure inherently provides noise immunity through frequency-based operation rather than voltage threshold comparison.
Solution Approach 2:
The patent changes the operating parameter from voltage threshold difference to oscillation frequency difference. By measuring frequency rather than voltage levels, the system achieves better noise immunity and eliminates the need for additional error correction hardware, thus reducing overall power consumption while maintaining reliability.
2Reliability
If oscillators are used to generate key values based on frequency difference, then noise immunity is improved, but the device requires relatively long time and consumes large power due to repeated oscillation cycles
Solution Approach 1:
The patent extracts only the essential frequency difference information from the oscillators without requiring multiple oscillation cycles. By using a single-cycle or limited-cycle measurement approach, the system achieves noise immunity through frequency comparison while avoiding the excessive power consumption associated with repeated oscillation cycles.
Solution Approach 2:
The patent rushes through the oscillation process by determining the key value within a single or limited number of oscillation cycles rather than requiring multiple cycles for averaging. This approach maintains noise immunity through frequency-based measurement while significantly reducing the time and power required compared to traditional multi-cycle oscillator PUFs.
3Reliability
If a large number of PUF cells are used for masking to ensure stable key generation, then reliability is improved, but chip area consumption increases significantly
Solution Approach 1:
The patent replaces the voltage amplifier PUF structure with an oscillator PUF structure that inherently provides better noise immunity. This substitution eliminates the need for extensive masking cells, thereby achieving reliable key generation with significantly reduced chip area.
Solution Approach 2:
By changing from voltage threshold measurement to frequency difference measurement, the patent achieves inherent noise immunity that reduces the need for additional masking cells. This parameter change allows for reliable key generation with fewer cells, thus reducing chip area consumption.
Data Source
AI summary
An exemplary embodiment of the present disclosure provides a physically unclonable function (PUF) cell capable of exhibiting a stable performance and showing an excellent repeatability while being less affected by environmental factors such as a noise, temperature, and bias voltage. The PUF cell generates an output value by combining a scheme of amplifying a threshold voltage difference and a scheme of amplifying an oscillation frequency difference. In an oscillator that generates oscillation signals of different frequencies, the frequency difference of the oscillation signals is amplified by alternately supplying bias voltages of different magnitudes generated by utilizing the threshold voltage difference to a plurality of stages in the oscillator.