Image Sensor RTN Pixels for Stable Cryptographic Key Regeneration
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Solution Overview
Problem
Existing cryptographic key generation methods face challenges in ensuring long-term security and deterministic generation without storage, particularly due to hardware changes over time and non-deterministic transitions in physically unclonable functions (PUFs).
Innovation Solution
Utilizing a semiconductor-based image sensor to capture images and identify pixels with random telegraph noise errors (RTN), determining a cryptographic key based on the distribution and behavior of these defective pixels, which can be regenerated with a predefined password for secure encryption and decryption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If physically unclonable functions (PUFs) are used to generate cryptographic keys from hardware characteristics, then key storage is eliminated and security is improved, but hardware changes over time cause key instability and non-deterministic transitions
Solution Approach 1:
The patent applies preliminary action by capturing multiple images of the image sensor before key generation to establish a baseline of pixel behavior. This pre-captured data is stored and used later to correct deviations caused by hardware changes, allowing the system to compensate for drift without storing the cryptographic key itself.
Solution Approach 2:
The system implements feedback by comparing current image sensor readings against previously captured reference images. When deviations are detected due to hardware changes, the system uses this feedback to adjust and correct the cryptographic key generation process, maintaining key stability despite hardware drift.
2Reliability
If complex cryptographic keys are stored in protected memory-storage systems, then security against unauthorized access is improved, but protection time and implementation complexity increase significantly
Solution Approach 1:
The patent applies discarding and recovering by eliminating the need to store cryptographic keys in protected memory. Instead, keys are continuously regenerated from image sensor data, which can be discarded after use. The system recovers the key generation capability by capturing new images when needed, avoiding the time-consuming process of implementing and maintaining protected storage systems.
3Ease of operation
If simple cryptographic keys are used that can be remembered by users, then ease of operation is improved, but security level decreases due to limited character string length
Solution Approach 1:
The system applies self-service by automatically generating cryptographic keys from image sensor data without requiring user input or manual key management. Users simply need to provide consent, and the system autonomously captures images, processes the pixel data, and generates secure keys, combining the security of complex keys with the simplicity of automatic operation.
4Reliability
If hardware structures are used to generate unique cryptographic keys, then key uniqueness and security are improved, but hardware aging and radiation cause key changes over time
Solution Approach 1:
The patent captures multiple reference images during an initial phase to establish a comprehensive baseline of hardware characteristics before degradation occurs. This preliminary data collection creates a robust reference that can compensate for future hardware changes due to aging or radiation exposure throughout the device's operational lifetime.
Solution Approach 2:
The system applies dynamics by making the key generation process adaptive rather than static. Instead of relying on fixed hardware characteristics that degrade over time, the system dynamically adjusts key generation by comparing current sensor readings against historical reference data, allowing it to accommodate hardware changes while maintaining key uniqueness and security.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Provides a stable and deterministic method for generating cryptographic keys tied to a hardware structure, ensuring secure encryption and decryption by regenerating keys with a known password, even when hardware characteristics change.
Implementation Method 1
Taking a plurality of images with an image sensor
Data Source
AI summary
A method for generating at least one cryptographic key includes taking a plurality of images with an image sensor, in particular, a CMOS image sensor, capturing pixels of the image sensor in at least one section or area of the image sensor which have a predefined error depending on the images taken and determining at least one cryptographic key depending on the captured pixels, that have the error, wherein the predefined error corresponds to a random telegraph noise error.