Debiasing Unit for Biased PUF Responses
Solution Overview
Problem
Fuzzy extractors used in Physically Unclonable Function (PUF)-based cryptographic key generation face challenges due to bias in PUF responses, leading to key leakage and reduced entropy, making existing solutions insecure and inefficient, especially when PUF responses have high bias or reduced entropy.
Innovation Solution
An electronic cryptographic device and method that incorporates a debiasing unit to reduce bias in PUF responses during the enrollment phase, allowing for the same cryptographic key to be reproduced in the reconstruction phase, using a debiasing unit to select and retain bits, and a key reconstruction unit to derive the cryptographic key from retained bits, while discarding biased bits to mitigate key leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fuzzy extractor is used to generate cryptographic keys from PUF responses, then key generation is enabled, but key leakage occurs due to bias in PUF responses
Solution Approach 1:
The patent extracts and removes biased bits from the PUF response through the debiasing unit, which identifies and discards bits that do not meet the bias threshold. This extraction of problematic data elements prevents key leakage while preserving the secure key generation function.
Solution Approach 2:
The patent converts the harmful bias in PUF responses into a beneficial filtering mechanism. The bias, which originally compromises security, is used as a criterion to identify and remove specific bits, transforming the problematic characteristic into a useful selection mechanism for enhancing key security.
2Reliability
If PUF responses with high bias are used, then key generation becomes insecure, but reducing bias requires additional processing
Solution Approach 1:
The patent segments the PUF response into individual bits and processes them independently through the debiasing unit. Each bit is evaluated against the bias threshold separately, allowing systematic removal of biased bits while maintaining the overall structure and functionality of the key generation system.
3Reliability
If bits are discarded to reduce bias, then key leakage is reduced, but entropy of the PUF response decreases
Solution Approach 1:
The patent changes the parameter of bit selection by introducing a bias threshold that dynamically determines which bits are retained and which are discarded. This parameter-based approach allows the system to adaptively filter bits based on their bias characteristics, balancing security requirements with entropy preservation.
Data Source
Figure 1a~1b
Figure 2~3
Figure 4a~4b
AI summary
An electronic cryptographic device (100) arranged to determine a cryptographic key. The cryptographic device has a physically unclonable function (PUF) (110), a debiasing unit (120) and a key reconstruction unit (150). The PUF is arranged to produce a first noisy bit string (112) during an enrollment phase and a second noisy bit string (114) during a reconstruction phase. The debiasing unit (120) is arranged to determine debiasing data (142) from the first noisy bit string during the enrollment phase. The debiasing data marks bits in the first noisy bit string as retained or discarded. The key reconstruction unit (150) is arranged to determine the cryptographic key from bits in the second noisy bit string marked as retained by the debiasing data, the cryptographic key being independent from bits in the second noisy bit string marked as discarded by the debiasing data.