PUF-Based Encryption Key Management for In-Vehicle Systems
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Solution Overview
Problem
Existing encryption key management systems for in-vehicle microcomputers are vulnerable to unjust acquisition and misuse, particularly due to fluctuations in physically unclonable function (PUF) data caused by manufacturing variations and environmental factors, leading to security defects and potential unauthorized access.
Innovation Solution
A method that generates device unique data, helper data, and a device unique ID to correct fluctuations, using these to create a stable Hash function for encryption key management, ensuring authentication before enabling key utilization, thereby preventing unjust acquisition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tamper-resistant technology utilizing PUF is employed throughout the microcomputer to prevent unjust acts, then security against unjust acquisition is improved, but the ability to conduct fault and defect analysis deteriorates
Solution Approach 1:
The system divides the microcomputer into two functional segments: a secure region containing the PUF and encryption key management that prevents unjust access, and a non-secure region that allows fault analysis. This segmentation enables simultaneous achievement of security and analyzability by isolating the security-critical components from the analysis-accessible components.
2Manufacturing precision
If the initial value of SRAM is used as PUF to generate device unique ID, then device uniqueness is improved, but repeatability deteriorates due to fluctuations from manufacturing variations and environmental factors
Solution Approach 1:
The system employs feedback mechanisms where the PUF output is continuously monitored and compared against stored reference values. When fluctuations occur due to environmental factors, the system uses feedback loops to compensate and maintain consistent device unique ID generation, thereby improving repeatability while preserving uniqueness.
Solution Approach 2:
The system changes operational parameters such as temperature compensation and voltage stabilization to minimize fluctuations in the PUF's initial SRAM values. By adjusting these parameters, the system maintains both the uniqueness derived from manufacturing variations and the repeatability needed for reliable operation across different environmental conditions.
3Ease of operation
If encryption key is written without measures against electronic eavesdropping, then ease of operation is improved, but security against unjust acquisition deteriorates
Solution Approach 1:
The system introduces an intermediary secure region that acts as a mediator between the external key writing interface and the actual encryption key storage. This intermediary layer provides security measures against eavesdropping while maintaining ease of operation, as the key writing process remains simple from the user perspective but is protected during transmission and storage by the secure intermediary region.
Data Source
AI summary
The first device, which utilize a cipher, generates device unique data by a PUF, and the second device generates one pair of helper data and a device unique ID on the basis of the generated device unique data. The device unique data has fluctuations caused by the generation environment, and regarding the fluctuations as an error to the device unique ID, the helper data serves as correction data for correcting the error. The second device generates a Hash function from the device unique ID and the encryption key. The second device writes one of the helper data and the Hash function to the first device first, and after authenticating the first device by the write, the other of the helper data and the Hash function is written in the first device. Decrypting the encryption key, the first device is allowed to utilize the cipher.