Threshold Logic Obfuscation Using Non-Functional Transmission Gates
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Solution Overview
Problem
Integrated circuits (ICs) using threshold logic elements lack obfuscation techniques to prevent reverse engineering, and existing obfuscation methods for Boolean networks increase power, delay, and area consumption.
Innovation Solution
Incorporating obfuscated transmission gates in threshold logic elements with differential sense amplifiers to obscure the threshold logic function, reducing power, delay, and area consumption while preventing reverse engineering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If obfuscation techniques are applied to threshold logic networks, then reverse engineering protection is improved, but device complexity increases
Solution Approach 1:
The patent introduces obfuscated transmission gates as intermediary elements that mediate between the input signals and the threshold logic function. These transmission gates are configured with threshold voltages that prevent them from affecting the logic function under normal operating conditions, yet they appear as functional components to reverse engineering tools, thereby providing protection without altering the underlying logic network complexity
Solution Approach 2:
The patent applies parameter changes by modifying the threshold voltage characteristics of transmission gates. By setting specific threshold voltage ranges for obfuscated transmission gates (different from operational ones), the patent creates a parameter-based distinction that protects the logic function while maintaining the same structural complexity. The obfuscated gates have threshold voltages that render them non-functional for logic operations but visible to reverse engineering analysis
2Reliability
If obfuscated transmission gates are added to threshold logic elements, then reverse engineering resistance is improved, but area consumption increases
Solution Approach 1:
The patent merges the obfuscation function with the existing transmission gate structure of threshold logic elements. Rather than adding separate obfuscation circuits, the obfuscated transmission gates are integrated directly into the input gate networks, combining the protective function with the existing area-efficient threshold logic architecture
Solution Approach 2:
The patent uses copies of standard transmission gate structures for obfuscation purposes. The obfuscated transmission gates replicate the physical structure and layout of operational transmission gates, making them indistinguishable in terms of area consumption, while differing only in their threshold voltage parameters that prevent logical functionality
3Reliability
If obfuscation is implemented in threshold logic networks, then security against piracy is improved, but power consumption increases
Solution Approach 1:
The patent extracts the obfuscation function from separate protective circuits and integrates it directly into the existing transmission gate network. By taking out the need for additional dedicated obfuscation hardware and embedding protection within the functional elements themselves, the patent avoids the power consumption overhead that would result from separate obfuscation circuits operating in parallel
Data Source
AI summary
A threshold logic element (TLE) is disclosed. The TLE includes a first input gate network, a second input gate network, and a differential sense amplifier. The first input gate network is configured to receive a first set of logical signals and the second input gate network configured to receive a second set of logical signals. The differential sense amplifier is operably associated with the first input gate network and the second input gate network such that the differential sense amplifier is configured to generate a differential logical output in accordance with a threshold logic function. To obfuscate the TLE, any number of obfuscated transmission gates can be provided in one or both of the input gate networks. The obfuscated transmission gates are obfuscated such that obfuscated transmission gates are incapable of effecting the threshold logic function of the TLE and thus hide the functionality of the TLE.