Non-Volatile Memory PUF Key Freezing Against Bit Error Drift
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Solution Overview
Problem
Existing physical unclonable function (PUF) technologies in integrated circuits face challenges with high bit error rates due to resistance drift in resistive random access memory (ReRAM), particularly at elevated temperatures, which affects the reliability of generated keys used for security protocols.
Innovation Solution
A method and system that utilize non-volatile memory cells to generate and store PUF keys, where the key generation is frozen using internal or external logic, and access is controlled through indicators or authentication protocols to prevent changes, ensuring a stable and reliable unique identifier or key.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ReRAM-based PUF is used to generate keys, then key generation capability is achieved, but bit error rate increases due to resistance drift at high temperatures
Solution Approach 1:
The patent changes the physical parameter basis from resistive memory (prone to temperature-induced drift) to non-volatile memory threshold voltages, which remain stable across temperature ranges. This parameter substitution resolves the contradiction by maintaining manufacturability while eliminating the reliability issue caused by resistance drift.
Solution Approach 2:
The patent uses the inherent manufacturing variability of non-volatile memory cells as a one-time, immutable source of entropy. Each cell's threshold voltage serves as a disposable, unchangeable random element that is read but never modified, providing reliable key material without the degradation problems of resistive memory.
2Duration of action of stationary object
If PUF keys are stored in non-volatile memory, then permanent storage is achieved, but changes to stored keys can occur due to lack of protection
Solution Approach 1:
The patent performs preliminary freezing of the PUF key in non-volatile memory during manufacturing or initialization. By permanently programming the key into the memory cells before deployment and preventing any subsequent write operations, the system achieves both permanent storage and compositional stability, as the key cannot be accidentally or maliciously modified.
Solution Approach 2:
The patent separates the key storage function from other memory operations by dedicating specific non-volatile memory cells exclusively to PUF key storage. This segmentation isolates the key data from general-purpose memory access and modification, ensuring that even if other memory operations occur, the key remains protected and unchanged.
3Reliability
If access control is implemented for PUF keys, then security is improved, but access complexity increases
Solution Approach 1:
The patent implements self-service security where the PUF key's inherent properties (stored in read-only fashion in non-volatile memory) provide automatic protection. The key material itself, derived from physical variability and frozen in place, serves as its own security mechanism without requiring complex external access control logic, authentication protocols, or additional protective circuitry.
Data Source
AI summary
A device which can be implemented on a single packaged integrated circuit or a multichip module comprises a plurality of non-volatile memory cells, and logic to use a physical unclonable function to produce a key and to store the key in a set of non-volatile memory cells in the plurality of non-volatile memory cells. The physical unclonable function can use entropy derived from non-volatile memory cells in the plurality of non-volatile memory cells to produce a key. Logic is described to disable changes to data in the set of non-volatile memory cells, and thereby freeze the key after it is stored in the set.