PUF Helper Data Generation for Reliable Secret Keys
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Solution Overview
Problem
Delay-based Physically Unclonable Functions (PUFs) suffer from low reliability due to environmental variations and noise, requiring complex error correction mechanisms that are not compatible with low-code devices.
Innovation Solution
An electronic system that generates secret information using a PUF circuit, which applies a set of challenges during an enrolment phase to measure physical variable differences and generates helper data bits based on these differences, using bit extraction functions that depend on reliability thresholds to produce reliable secret keys without the need for error correction mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If delay-based PUFs are used to generate secret keys, then the PUF provides unique and unpredictable responses, but the reliability of the PUF output deteriorates due to environmental variations and noise
Solution Approach 1:
The patent applies preliminary action by performing an enrolment phase before actual key generation. During enrolment, multiple challenges are applied to the PUF and the responses are stored to characterize the PUF's behavior under different conditions. This preliminary characterization allows the system to compensate for environmental variations during subsequent operations, ensuring reliable key generation without requiring complex error correction mechanisms.
2Reliability
If error correction mechanisms are added to improve PUF reliability, then the reliability improves, but the device complexity increases
Solution Approach 1:
The patent applies self-service by enabling the PUF system to compensate for its own environmental variations through the enrolment phase. The system uses the PUF's unique physical characteristics and the stored response data to automatically adjust and ensure reliable output without requiring external error correction mechanisms. The PUF essentially serves itself by leveraging its inherent uniqueness and the preliminary characterization data.
3Reliability
If conventional error correction codes are used to ensure reliable PUF bits, then the reliability improves, but the ease of manufacture deteriorates due to compatibility issues with low-code devices
Solution Approach 1:
The patent applies the extraction principle by removing complex error correction code structures from the system. Instead of using conventional ECC mechanisms that require sophisticated coding and decoding capabilities, the patent extracts and utilizes only the essential PUF response characteristics during the enrolment phase. This simplified approach maintains reliability while being fully compatible with low-code devices that lack advanced error correction capabilities.
Data Source
AI summary
Embodiments of the invention provide an electronic system for generating secret information comprising a Physically Unclonable Function (PUF) circuit, the PUF circuit being configured to provide a difference between two values of a physical variable of the PUF in response to a challenge applied to the PUF circuit. The system is configured to apply a set of challenges during an enrolment phase, and measure the physical variable difference provided by the PUF in response to each challenge. The system comprises:a helper data generator (2) configured to generate a helper data comprising a set of bits, a bit of the helper data being generated in association with each applied challenge, the helper data generator being configured to generate each helper data bit from the physical variable difference provided by the PUF in response to the application of the associated challenge,a secret information generator (3) configured to generate a secret key comprising at least one bit during a usage phase, each bit of the key being generated by applying a challenge among the set of challenges, the secret information generator (3) being configured to determine each bit of the key from the helper data bit corresponding to the applied challenge, and from the physical variable difference provided by the PUF in response to the applied challenge.