Freezing PUF Keys in Charge-Trapping Memory
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Solution Overview
Problem
Existing technologies face challenges in generating and maintaining reliable physical unclonable function (PUF) keys for secure applications, particularly in non-volatile memory devices, due to high bit error rates caused by manufacturing variability and environmental factors like temperature, which affect the stability and predictability of resistance in ReRAM-based PUFs.
Innovation Solution
A method and circuit design that utilizes charge-trapping non-volatile memory cells to generate stable PUF-based data sets with zero or very low bit error rates by establishing variant thresholds within memory cells, and then freezing these keys through internal or external logic to prevent changes, ensuring their permanence and security.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If ReRAM-based PUF is used to generate unique keys, then key generation capability is improved, but bit error rate increases due to manufacturing variability and environmental factors
Solution Approach 1:
The patent applies preliminary action by establishing a starting distribution of thresholds in memory cells before generating the PUF key. This pre-conditioning step ensures that the memory cells are in a known state, which reduces variability and bit error rates during subsequent key generation operations.
Solution Approach 2:
The patent changes physical parameters by establishing variant thresholds within memory cells through controlled charge trapping. By manipulating threshold voltage distributions and using read margins, the system transforms the physical state of memory cells to achieve stable, low-error PUF key generation despite manufacturing variations.
2Adaptability or versatility
If PUF keys are generated using manufacturing variability, then uniqueness is improved, but predictability increases making security weaker
Solution Approach 1:
The patent applies local quality by creating spatially varying threshold distributions across different memory cells. Each cell develops unique local characteristics through controlled charge trapping, ensuring that the PUF key reflects genuine physical variations rather than predictable patterns.
Solution Approach 2:
The patent converts the harmful effect of manufacturing variability into a beneficial security feature. By deliberately exploiting threshold voltage variations and using read margins to capture these variations, the system transforms what was previously an error source into a unique, unpredictable identifier for each device.
3Stability of the object's composition
If charge-trapping memory cells are used to establish variant thresholds, then stability is improved, but device complexity increases
Solution Approach 1:
The patent applies universality by using standard charge-trapping memory cells for multiple purposes: normal data storage and PUF key generation. The same memory array and control logic serve both functions, avoiding the need for separate dedicated PUF hardware and reducing overall device complexity.
Solution Approach 2:
The patent applies self-service by enabling memory cells to automatically establish their own unique threshold characteristics through controlled charge trapping. The cells self-configure their threshold distributions based on physical variations, eliminating the need for complex external calibration or programming equipment.
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
The solution provides a reliable and secure method to generate and store PUF keys with low bit error rates, enhancing the security and stability of PUF-based systems in various environments, including IoT devices, by using charge-trapping memory cells to create unique identifiers and encryption keys.
Implementation Method 1
A method and circuit design that utilizes charge-trapping non-volatile memory cells to generate stable PUF-based data sets with zero or very low bit error rates by establishing variant thresholds within memory cells
Data Source
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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.