PUF Security Key Reliability via Sorted Reference Cell Selection
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Solution Overview
Problem
Physical unclonable function (PUF) devices in semiconductor security systems face reliability issues due to variations in process, voltage, and temperature (PVT) factors, leading to errors in generated security keys.
Innovation Solution
A security device with a controller and PUF cell array that sorts raw data from multiple PUF cells, selects target and reference cells, reads sensing data, and determines target bits to generate a security key, thereby improving key reliability by using a sorted list and variable window techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If PUF generates a random key depending on PVT variations, then uniqueness of the key is improved, but reliability of the key deteriorates due to errors from environmental factors
Solution Approach 1:
The patent introduces a controller as an intermediary between the PUF cells and the key generation process. The controller sorts raw data from multiple PUF cells, selects target and reference cells, and determines final key bits based on comparisons. This intermediary processing step filters out errors caused by PVT variations while preserving the uniqueness property of PUF-generated keys.
Solution Approach 2:
The patent implements a feedback mechanism where the controller reads sensing data from both target PUF cells and reference PUF cells, compares their outputs, and uses the comparison results to determine reliable key bits. The reference cells provide feedback information that helps compensate for environmental variations affecting the target cells, thereby improving key reliability without sacrificing uniqueness.
2Reliability
If multiple PUF cells are used to improve key reliability, then error reduction is improved, but device complexity increases
Solution Approach 1:
The patent segments the PUF cell array into groups of target cells and reference cells, with each group serving a specific function. The controller processes these segmented groups separately through sorting and selective reading, which organizes the complexity into manageable units. This segmentation allows reliable key generation using a controlled number of PUF cells while maintaining systematic control over the processing complexity.
Solution Approach 2:
The patent performs preliminary sorting of raw data from all PUF cells before actual key generation. The controller creates a sorted list of PUF cell addresses based on their raw data values, and this pre-organized structure enables efficient selection of target and reference cells during key generation. This preliminary action reduces the complexity of real-time processing by establishing an ordered framework in advance.
3Reliability
If PUF cells are used for security key generation, then hardware-based security is improved, but errors from PVT variations increase
Solution Approach 1:
The patent converts the harmful effect of PVT variations into a beneficial feature by using reference PUF cells that experience similar environmental conditions. The differences between target and reference cell outputs, rather than being purely error signals, become the basis for generating reliable key bits through comparison. This approach transforms the unavoidable physical variations into a mechanism for error correction and reliability improvement.
Solution Approach 2:
The patent changes the operational parameters of the PUF system by implementing variable window techniques and dynamic selection of target and reference cells based on sorted raw data. Instead of using fixed PUF cell configurations, the system adapts its parameter selection based on the actual measured values, optimizing the balance between security, reliability, and error tolerance under varying environmental conditions.
Data Source
AI summary
An operation method of a security device which includes a plurality of physical unclonable function (PUF) cells includes selecting a target PUF cell of the plurality of PUF cells, selecting at least two reference PUF cells of the plurality of PUF cells based on a sorted list, reading a plurality of sensing data from the target PUF cell and the at least two reference PUF cells, and determining a target bit corresponding to the target PUF cell based on the plurality of sensing data to output the determined target bit.