Scan-Chain PUF Authentication Using Challenge Logic
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Solution Overview
Problem
Semiconductor devices face challenges in resisting tampering and hacking due to limitations in existing physically unclonable function (PUF) security measures, which are not effectively resistant to unauthorized access or cloning.
Innovation Solution
A method is introduced that generates a second physically unclonable function based on the power-up values of flip-flops in scan chain logic, using physical and electrical characteristics unique to each semiconductor device, combined with combinatorial logic operations and challenge words, to enhance security features and prevent unauthorized access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing PUF security measures are used, then device identification is achieved, but resistance to tampering and hacking is insufficient
Solution Approach 1:
The patent implements nested PUF construction where a second PUF is generated within the structure of the first PUF. The second PUF uses the first PUF's power-up values as input to combinatorial logic, creating a layered security structure where each PUF level enhances the other, similar to nested dolls where smaller elements are contained within larger ones.
Solution Approach 2:
The patent performs preliminary generation and storage of the second PUF during manufacturing or initial setup. The second PUF values are pre-computed based on the first PUF characteristics and stored securely, so that during operation only authentication against these pre-generated values is needed, reducing real-time computational complexity while maintaining high security.
2Reliability
If strong PUFs are generated using multiple challenge words and combinatorial logic, then security is improved, but manufacturing complexity increases
Solution Approach 1:
The patent uses standard scan chain logic and combinatorial logic circuits that serve dual purposes: their normal function for device operation and their function as PUF generation components. The scan chains are used both for testing/debugging and for generating the first PUF values, while the combinatorial logic performs both data processing and second PUF generation, reducing the need for dedicated security hardware.
3Ease of operation
If PUF values are stored and used for authentication, then device identification is achieved, but vulnerability to unauthorized access increases
Solution Approach 1:
The patent transforms the authentication mechanism by changing from storing raw PUF values to storing processed second PUF values that result from passing first PUF values through combinatorial logic with challenge words. This parameter transformation ensures that even if first PUF values are compromised, the authentication security is maintained through the one-way nature of the logical operations.
Data Source
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AI summary
A method for controlling access to a chip includes obtaining first values of a first physically unclonable function of the chip, obtaining second values that correspond to at least one challenge word, performing a simulation based on the first values and the second values, and generating an authentication result for the chip based on results of the simulation. The simulation may generate responses to logical operations corresponding to combinatorial logic in the chip, and the logical operations may be performed based on a predetermined sequence of the first values and the second values. The chip may be authenticated based on a match between the responses generated by the simulation and a second physically unclonable function of the chip.