Multi-Word Line PUF Read Circuit for Noise Immunity
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Solution Overview
Problem
Existing physically unclonable function (PUF) systems, such as those using static random-access memory (SRAM), face challenges in predictability due to manufacturing variations, temperature, power supply, and noise, limiting their ability to generate a unique digital code effectively.
Innovation Solution
Implementing a data processing system and method that activates multiple word lines and bit lines during a read operation in a memory array, using a comparator to generate a digital code by comparing currents from multiple memory cells, thereby increasing signal difference and noise immunity, and expanding the challenge-response space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single word line is activated during read operation in traditional PUF systems, then the read operation is simple, but the signal difference is small and noise immunity is poor
Solution Approach 1:
The patent merges multiple word lines (e.g., WL0 and WL1) to be activated simultaneously during the read operation. This combining of multiple word lines increases the signal difference between bit lines, thereby improving noise immunity and reliability of the PUF response without requiring fundamental changes to the memory architecture.
2Adaptability or versatility
If multiple responses are needed for a challenge, then the cryptographic security is improved, but a single SRAM power-up state can only generate one digital code
Solution Approach 1:
The patent introduces dynamic control of word line selection through a row address input. By dynamically selecting different combinations of word lines based on the row address, the system can generate multiple different responses from the same physical memory cells, thereby expanding the challenge-response space without adding multiple physical PUF arrays.
Solution Approach 2:
The patent adds the dimension of word line combination selection to the traditional single-bit PUF response. Instead of only reading from a single memory location, the system now reads from multiple memory locations simultaneously by activating multiple word lines, creating additional degrees of freedom for generating diverse responses.
3Reliability
If manufacturing variations and environmental factors are present, then the PUF produces unpredictable responses, but this also causes instability in the digital code generation
Solution Approach 1:
The patent converts the harmful effect of manufacturing variations into a benefit by using multiple word lines. The variations in threshold voltages and transistor characteristics across different memory cells, when combined through multiple word line activation, create a more robust and stable digital code that is less sensitive to individual cell variations.
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 enhances noise immunity and increases the number of possible responses from a PUF array, making it more suitable for generating cryptographic keys and signatures by improving the robustness of the digital code generation process.
Implementation Method 1
comparing currents from multiple memory cells, thereby increasing signal difference and noise immunity
Data Source
AI summary
A data processing system and method for generating a digital code for use as a physically unclonable function (PUF) response is provided. The method includes activating a plurality of word lines for a read operation. A first bit line is coupled to a first input of a comparator during the read operation. A second bit line is coupled to a second input of the comparator during the read operation. A current is generated on each of the first and second bit lines. The currents on the first and second bit lines are converted to voltages. The voltage on the first bit line is compared to the voltage on the second bit line. A logic bit is output from the comparator as part of the digital code, a logic state of the logic bit is determined in response to the comparison. By selecting multiple word lines to determine a PUF response, noise immunity is improved.