PUF Cell Array Security Key Generation via Current Comparison
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Solution Overview
Problem
Physical unclonable function (PUF) devices face reliability issues due to errors caused by environmental factors such as process, voltage, and temperature variations, leading to inconsistent key generation in hardware-based security systems.
Innovation Solution
A security device with a PUF cell array that includes a controller, decoder, bit line selection circuit, and bit determiner, which selects a target PUF cell, applies voltage, and generates a security key based on the difference between the target current and the sum current from other PUF cells, eliminating the need for separate analog-to-digital converters and reference data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PUF cells are used to generate security keys, then hardware-based security is achieved, but errors occur due to environmental factors reducing reliability
Solution Approach 1:
The patent implements a feedback mechanism where the generated security key is verified against expected properties (such as bit distribution statistics). If the key fails verification, the process retries with different PUF cell selections or parameters until a valid key is generated, thereby compensating for environmental variations and improving reliability
Solution Approach 2:
The system performs preliminary characterization of PUF cells during manufacturing to identify cells with stable responses. This pre-screening data is stored and used during operation to select only reliable PUF cells for key generation, preventing errors from unstable cells before they affect security key reliability
2Measurement precision
If separate analog-to-digital converters and reference data are used, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent merges the analog-to-digital conversion function directly into the PUF cell array structure itself, using the inherent physical properties of the PUF cells to provide both the security function and the measurement reference. This eliminates separate ADC circuits and external reference data storage, reducing device complexity while maintaining measurement precision through the physical unclonability of the PUF cells
Solution Approach 2:
The PUF cell array serves multiple functions simultaneously: it generates the security key, provides the measurement reference through its physical properties, and performs the comparison function. This multi-functionality eliminates the need for separate dedicated components, reducing overall device complexity while maintaining precision
Data Source
AI summary
A security device includes a physical unclonable function (PUF) cell array that includes a plurality of PUF cells connected with a first word line, a controller that selects a target PUF cell of the plurality of PUF cells and outputs a control signal based on the target PUF cell, a decoder that applies a first voltage to the first word line in response to the control signal, a bit line selection circuit that outputs a target current across a bit line connected with the target PUF cell and a sum current corresponding to a sum of currents across the remaining bit lines connected with other PUF cells, and a bit determiner that outputs a target bit of the target PUF cell based on the target current and the sum current, and the security device generates a security key based on the target bit for responding to an authentication requests.