PUF-Film Security for Embedded Systems
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Solution Overview
Problem
Current security solutions for protecting multiple-chip embedded systems against physical attacks are hindered by the need for battery-powered tamper-detection mechanisms, which increase bulk, weight, and vulnerability to temperature fluctuations, while also being ineffective for aftermarket protection of Commercial-Off-The-Shelf components and incapable of detecting offline or online attacks.
Innovation Solution
A method for producing PUF-films with a dielectric layer of varying thickness, integrated with structured electrode layers, allowing for capacitive measurements that serve as both a secure key and integrity verification without the need for batteries, using additive printing processes to create a robust, tamper-evident security structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If battery-backed tamper-detection mechanisms are used, then continuous monitoring capability is improved, but system bulk, weight, and temperature vulnerability increase
Solution Approach 1:
The patent extracts and eliminates the battery component from the security system by transitioning from battery-backed tamper detection to battery-less PUF-based security. The PUF (Physical Unclonable Function) structure generates cryptographic keys from inherent physical variations in the semiconductor device, removing the need for external power sources during security operations.
Solution Approach 2:
The PUF structure utilizes the device's own inherent physical characteristics (manufacturing variations, material properties) to generate security keys and perform tamper detection. The system serves itself by leveraging its unique physical fingerprint rather than requiring external battery-powered monitoring components.
2Reliability
If battery-backed tamper-detection mechanisms are used, then continuous monitoring capability is improved, but device robustness and temperature stability worsen
Solution Approach 1:
The battery component that causes temperature fluctuations and robustness issues is extracted and removed from the system. The PUF-based security operates without batteries, eliminating the thermal and reliability problems associated with battery-powered monitoring.
3Reliability
If resistance-based tamper detection is used, then integrity verification is improved, but compatibility with PUF measurement systems worsens
Solution Approach 1:
The patent merges integrity verification and PUF measurement into a single unified capacitive measurement system. The same capacitive sensors used to read PUF properties also detect tampering attempts, eliminating the need for separate resistance-based monitoring circuits and their associated Wheatstone bridges.
Solution Approach 2:
The capacitive measurement system serves multiple functions: it reads PUF properties for cryptographic key generation and simultaneously detects tampering attempts. This multi-functional approach replaces the specialized resistance-based monitoring with a universal capacitive sensing mechanism.
4Measurement precision
If capacitive sensing is used for PUF measurement, then PUF property extraction is improved, but integrity verification capability worsens
Solution Approach 1:
The capacitive sensing system is designed to perform dual functions: extracting PUF properties and verifying integrity. The measurement circuitry analyzes capacitance values to both read the unique physical fingerprint and detect any physical tampering, combining previously separate functions into one system.
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 solution provides reliable, battery-less protection against physical attacks by leveraging the unique electrical properties of the PUF-films for cryptographic key generation and integrity checks, enhancing the security and durability of embedded systems without the drawbacks of battery-powered systems.
Implementation Method 1
a printed dielectric layer (28) having a variable thickness in the dielectric material and a structured electrode layer (32) being arranged at the dielectric layer (28), wherein the structured electrode layer (32) is influenced with respect to an electric measurement value due to the variable thickness
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
A PUF-film comprises a flat circuit structure comprising a plurality of circuit elements and comprises a flat electric shield. The circuit structure is evaluable with respect to a plurality of electric capacitance values being arranged between the plurality of circuit elements. The electric shield at least partially covers the circuit structure and provides for a counter reference electrode of the plurality of electric capacitance values.