Threshold-Voltage Camouflaged Logic Gate for Low-Overhead IC Security
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Solution Overview
Problem
Conventional camouflage techniques for preventing circuit theft through reverse engineering often increase chip area, power consumption, and delay time, while also being costly and difficult to integrate with existing processes, and they complicate interfacing with other logic due to dynamic operations.
Innovation Solution
A memory-type camouflaged logic gate using transistors with different threshold voltages, combined with a multiplexer, allows for selective operation as various logic gates based on memory data, preventing reverse engineering by adjusting output signals and reducing the number of candidate logic gates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional camouflage techniques are applied to prevent circuit theft through reverse engineering, then security against reverse engineering is improved, but chip area increases
Solution Approach 1:
The patent changes the threshold voltage parameter of transistors to create different functional behaviors. By using transistors with different threshold voltages (Vth) in the memory cell, the same physical structure can represent multiple logic gates (NAND, NOR, XOR) depending on the Vth values, thereby preventing reverse engineering without increasing chip area
Solution Approach 2:
The memory cell structure is designed to serve multiple functions by varying transistor threshold voltages. The same memory cell can emulate different logic gates (NAND, NOR, XOR) based on the Vth values of its transistors, making a single structure universal for multiple logic functions and avoiding the need for separate camouflaged structures for each gate type
2Reliability
If conventional camouflage techniques are applied to prevent circuit theft through reverse engineering, then security against reverse engineering is improved, but power consumption increases
Solution Approach 1:
The patent utilizes threshold voltage as a controlling parameter to determine logic gate functionality. By adjusting Vth values of transistors in the memory cell, the circuit can switch between different logic operations without requiring additional power-intensive components or structures, thus maintaining low power consumption while achieving security
3Reliability
If conventional camouflage techniques are applied to prevent circuit theft through reverse engineering, then security against reverse engineering is improved, but delay time increases
Solution Approach 1:
The patent changes transistor threshold voltage parameters to achieve different logic functions within the same circuit structure. This approach avoids the need for complex additional circuitry that would increase delay time, as the Vth-based differentiation occurs at the transistor level without adding significant propagation delays
4Reliability
If conventional camouflage techniques are applied to prevent circuit theft through reverse engineering, then security against reverse engineering is improved, but manufacturing complexity increases
Solution Approach 1:
The patent achieves security by varying transistor threshold voltage parameters, which can be controlled during standard manufacturing processes through techniques like doping concentration adjustment. This approach maintains compatibility with existing manufacturing workflows without requiring complex additional fabrication steps or specialized equipment
5Reliability
If conventional camouflage techniques are applied to prevent circuit theft through reverse engineering, then security against reverse engineering is improved, but interfacing with static logic becomes difficult
Solution Approach 1:
The memory cell is designed with a unified structure that can represent multiple logic gates through threshold voltage variations. This universal design maintains consistent input-output interfaces regardless of which logic function is active, making interfacing with static logic straightforward and avoiding the need for different interface circuits for different gate types
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 effectively prevents chip theft through reverse engineering without increasing chip area, power consumption, or delay, while maintaining compatibility with static logic and reducing costs, thus overcoming limitations of previous methods.
Implementation Method 1
respective threshold voltages of the first P-channel transistor and the second P-channel transistor may be different from each other, or respective threshold voltages of the first N-channel transistor and the second N-channel transistor may be different from each other
Data Source
AI summary
Disclosed herein is a memory-type camouflaged logic gate using transistors having different threshold voltages. The camouflaged logic gate may include two or more candidate logic gates, memory, the output signal of which is adjusted based on two or more transistors having different threshold voltages, and a multiplexer for selectively outputting the output of one of the two or more candidate logic gates depending on the output signal of the memory.