PUF Cell Signature Key Generation via State Change Ordering
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Solution Overview
Problem
Existing methods for generating signature keys using physical unclonable function (PUF) cells are time inefficient and require waiting for all PUF cells to become stable, which is impractical for longer bit lengths, especially for high-security applications where speed and efficiency are crucial.
Innovation Solution
A system and method that sets the state of multiple PUF cells to a uniform level, samples their state changes, and generates a signature key based on the order of change in a subset of PUF cells, rather than waiting for all cells to stabilize, using a state determination device, lookup table, register, and encoder to efficiently produce a signature key with a desired bit length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all PUF cells are waited to stabilize before generating signature key, then the stability and reliability of the signature key is improved, but the time required for key generation increases significantly
Solution Approach 1:
The patent applies partial action by sampling only a subset of PUF cells rather than waiting for all cells to stabilize. The system selectively chooses m PUF cells out of n total cells, where m < n, and generates the signature key based on this partial sample. This reduces the waiting time while maintaining sufficient reliability through the statistical properties of PUF cell behavior.
Solution Approach 2:
The patent segments the PUF cell population into multiple groups and selectively samples from these segments. By dividing the n PUF cells into subsets and choosing m cells for sampling, the system can process a manageable portion of the total cells, reducing the overall stabilization waiting time while still generating a secure signature key of desired bit length.
2Reliability
If a larger number of PUF cells are used to generate longer bit length signature keys, then the security strength is improved, but the time required for key generation increases
Solution Approach 1:
The patent enables generation of signature keys with arbitrary bit lengths by sampling m PUF cells, where m can be chosen independently of the total n cells available. This allows the system to generate longer signature keys (higher security) without proportionally increasing the waiting time, as only a subset m of the total n cells needs to be processed.
Solution Approach 2:
The patent changes the parameter relationship between total PUF cells (n) and sampled PUF cells (m) to optimize performance. By adjusting the sampling size m independently from the total cell count n, the system can achieve desired security levels (bit length) without linearly increasing processing time, thus decoupling security strength from generation time.
3Productivity
If sampling rate is increased to reduce key generation time, then the productivity is improved, but the measurement precision of PUF cell state changes may be affected
Solution Approach 1:
The patent applies preliminary action by pre-setting all PUF cells to a known initial state (e.g., all zeros) before sampling begins. This preparation ensures that when cells are sampled at high speed, their transitions from the predetermined state are easily detectable and measurable, maintaining precision even with increased sampling rates. The known initial state provides a reference point for accurate detection.
Solution Approach 2:
The patent enables the PUF cells to self-indicate their state changes through natural physical phenomena (e.g., oscillation frequencies, relaxation times) without requiring complex external measurement equipment. The cells' inherent physical properties provide the measurement signal, allowing high-speed sampling without compromising precision, as the measurement burden is reduced to detecting natural cell behavior.
Data Source
AI summary
A method for utilizing a plurality of physical unclonable function (PUF) cells to generate a signature key with a desired bit length is provided. The method includes setting a state of each of the plurality of PUF cells to a uniform level; obtaining an order of change in the state of at least a portion of the plurality of PUF cells; and generating the signature key at least based on the order.