Bus-Keeper PUF Readout for Stable IDs and Reduced Aging
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Solution Overview
Problem
Physical unclonable functions (PUFs) face challenges in maintaining consistent digital identifiers across power cycles due to manufacturing variations, leading to errors and the need for error correction, while also requiring efficient power management to reduce aging effects and minimize size and power consumption.
Innovation Solution
A PUF system comprising bus-keepers that settle into stable states based on random physical characteristics, utilizing a reading circuit with multiplexers for selection and a power domain for controlled power supply, allowing for reduced noise and efficient power usage, enabling multiple read cycles and on-chip implementation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If error correction procedures using helper data are implemented to correct manufacturing variations, then digital identifier consistency across power cycles is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent extracts only the essential read functionality from memory cells, removing write capability and address decoding logic. This creates a simplified memory structure that retains enough functionality to read the PUF identifier while eliminating complex error correction circuitry. The simplification is achieved by taking out unnecessary components rather than adding error correction to full-featured memory.
Solution Approach 2:
Instead of starting with full memory and adding error correction, the patent inverts the approach by starting with minimal read-only functionality and only including what is absolutely necessary. The memory structure is designed backwards from conventional memory - removing features rather than adding them - to achieve the desired simplicity while maintaining reliability.
2Ease of operation
If conventional memory structures with address decoders are used, then read capability is improved, but chip area and power consumption increase
Solution Approach 1:
The patent removes address decoders and write logic from conventional memory structures, retaining only the essential read functionality. This extraction of unnecessary components dramatically reduces chip area while maintaining the ability to read PUF data. The memory cells are connected directly to read circuitry without complex addressing logic.
Solution Approach 2:
The patent applies different functionality to different parts of the memory structure - specifically making the entire memory read-only without write capability. This local quality change (making specific regions non-writable) simplifies the overall structure by eliminating the need for write logic and address decoders in those regions, reducing chip area.
3Ease of operation
If continuous power supply to memory elements is maintained, then operational readiness is improved, but aging effects and power consumption increase
Solution Approach 1:
The patent implements periodic power cycling of the memory elements - powering them up only when reading is needed and powering down between reads. This periodic action reduces continuous power consumption and mitigates aging effects while maintaining operational readiness when required. The system accepts brief startup delays in exchange for significant energy savings.
Solution Approach 2:
The patent makes the power supply to memory elements dynamic rather than static - the memory can be powered up or down based on operational needs. This dynamic power management allows the system to adapt power consumption to actual usage patterns, reducing energy loss during non-operational periods while ensuring readiness when reads are required.
Data Source
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AI summary
A physical unclonable function is provided 100, comprising a plurality of bus-keepers 110, each bus-keeper of the plurality of bus-keepers 110 being configured to settle into one of at least two different stable states upon power-up, the particular stable state into which a particular bus-keeper of the plurality of bus-keepers settles being dependent at least in part upon the at least partially random physical characteristics of the particular bus-keeper, and a reading circuit 120 for reading the plurality of stable states into which the plurality of bus-keepers settled after a power-up, the plurality of bus-keepers being read-only.