Non-volatile Memory PUF Using Access Transistor Variability
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Solution Overview
Problem
Current semiconductor memory solutions, such as SRAM-based physical unclonable functions (PUFs), face challenges in providing sufficient security due to limited mismatch variability, vulnerability to environmental changes, and the need for additional memory blocks and complex logic, which can be exploited by attackers.
Innovation Solution
A non-volatile memory system utilizing access transistors with large threshold voltage variations as a PUF, where the measurement unit compares electrical characteristics, such as currents or voltages, to generate die-individual encryption keys without relying on flash storage elements, thereby enhancing security with minimal design changes and redundancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SRAM-based PUF is used to generate identification information, then random data can be generated for security purposes, but the mismatch variability is limited and the system becomes vulnerable to environmental changes
Solution Approach 1:
The patent changes the physical parameter basis from SRAM threshold voltage mismatch to access transistor threshold voltage mismatch. This parameter change provides larger variability range and better environmental stability, resolving the contradiction between security reliability and environmental vulnerability by selecting a more robust physical parameter for PUF operation
2Reliability
If additional memory blocks and complex logic are added to enhance security, then security certification can be achieved, but the device complexity increases and potential attack surfaces expand
Solution Approach 1:
The patent makes the access transistors serve dual functions: normal memory access operations and PUF-based security operations. By measuring threshold voltage variations during regular access transistor operation rather than requiring separate PUF circuitry, the invention achieves security certification while maintaining simple device architecture and avoiding additional attack surfaces
3Loss of information
If threshold voltage variations are measured for PUF functionality, then unique identification can be obtained, but the measurement precision requirements increase system complexity
Solution Approach 1:
The patent employs self-service by using the access transistors themselves to perform the measurement function. The transistors that naturally exhibit threshold voltage variations are the same transistors used to conduct the measurement, eliminating the need for separate high-precision measurement equipment and reducing overall system complexity while maintaining identification uniqueness
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
This approach increases security by leveraging the inherent variability of access transistors in non-volatile memories, providing unique encryption keys for each die without additional memory blocks, while being resilient to environmental changes and reducing the risk of key extraction.
Implementation Method 1
A non-volatile memory system utilizing access transistors with large threshold voltage variations as a PUF, where the measurement unit compares electrical characteristics, such as currents or voltages
Data Source
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AI summary
In accordance with a first aspect of the present disclosure, a non-volatile memory is provided, comprising: a plurality of storage elements; a plurality of access transistors, said access transistors being connected to one or more of said storage elements; a measurement unit, wherein said measurement unit is configured to measure a variation between electrical characteristics of said access transistors; a processing unit configured to use said variation between electric characteristics as a physical unclonable function. In accordance with a second aspect of the present disclosure, a corresponding method of manufacturing a non-volatile memory is conceived.