Adaptive PUF Post-Processing for Long-Term Key Correctness
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Solution Overview
Problem
Existing PUF post-processing implementations face challenges in balancing hardware cost with yield rate due to fixed error rate thresholds, which can lead to system failure when actual error rates exceed these thresholds, especially under conditions like device aging.
Innovation Solution
Adaptive post-processing of PUFs involves detecting noisy PUF bits, correcting them initially, and storing their locations and values in an Override Bits Table to override them in future key generations, reducing the need for error correction and maintaining long-term correctness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed error rate threshold is used in PUF post-processing, then the system can be designed with fixed hardware cost, but the system fails when actual error rates exceed the threshold due to device aging or other conditions
Solution Approach 1:
The patent implements dynamic error correction by maintaining an override bits table that is updated over time. The system transitions from static fixed-threshold error correction to dynamic adaptation where the override bits table evolves as noisy bits are detected and corrected, allowing the system to adapt to changing error rates while maintaining reliability
Solution Approach 2:
The system performs self-correction by automatically detecting noisy PUF bits through error correction, storing their locations in the override bits table, and using these stored locations to preemptively correct errors in future key generations without external intervention
2Reliability
If the fixed error rate threshold is increased to accommodate higher error rates, then the system maintains operation under worse conditions, but the hardware cost for error correction increases
Solution Approach 1:
The system performs preliminary error correction by detecting and correcting noisy PUF bits before they cause key generation failures. The override bits table is proactively populated with locations of noisy bits, enabling preemptive correction that prevents errors from propagating to the final key output
Solution Approach 2:
The patent extracts and isolates the error correction functionality into a separate override bits table mechanism, distinct from the main PUF key generation path. This extraction allows error correction to be performed efficiently on specific noisy bits rather than requiring comprehensive hardware protection for all possible error scenarios
3Ease of manufacture
If fixed Error Correction Logic is designed for a given error rate, then the hardware cost is fixed, but the system fails when actual error rates differ from the design assumptions
Solution Approach 1:
The patent implements dynamic error correction by maintaining an override bits table that is updated over time. The system transitions from static fixed-threshold error correction to dynamic adaptation where the override bits table evolves as noisy bits are detected and corrected, allowing the system to adapt to changing error rates while maintaining reliability
Solution Approach 2:
The system incorporates feedback mechanisms where error correction outcomes are used to update the override bits table. When noisy bits are detected during error correction, their locations are fed back into the override bits table for future correction, creating a continuous improvement loop that enhances reliability
Data Source
AI summary
In accordance with embodiments disclosed herein, there is provided systems and methods for providing a post-processing mechanism for physically unclonable functions. An integrated circuit includes a physically unclonable function (PUF) unit including an adaptive PUF logic. The adaptive PUF logic receives a PUF response having a plurality of bits. The adaptive PUF logic also determines whether a record exists for bit among the plurality of bits in the PUF response. The record includes a stored bit location and a stored bit value corresponding to the stored bit location. The adaptive PUF logic also overrides a bit value of the bit in the PUF response with the stored bit value when it is determined that the record exists for the bit in the PUF response. The bit value of the bit in the PUF response is different from the stored bit value.