Field Device Tamper Protection via Physical Fingerprinting

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Solution Overview

Problem

Existing tamper protection methods for field devices are complex, costly, and lack simplicity in implementation and maintenance, while providing insufficient security against physical manipulation.

Innovation Solution

A method involving the arrangement of test elements within a field device's sheath, using a pseudorandom process to create a unique physical fingerprint, which is measured and compared against stored data to detect any tampering, employing various signal types and storage methods for enhanced security.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If hardware security integrated circuits with sensors are used to detect unauthorized opening, then tamper protection capability is improved, but device complexity and cost increase

Engineering Contradiction:

Improvetamper protection capabilityVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical tamper detection systems (sensors, switches) with a simplified physical fingerprinting approach using test signals passed through the sheath material itself. The sheath's inherent physical properties (attenuation, phase shift, reflection) serve as the security feature, eliminating the need for additional mechanical detection components.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The sheath material itself provides the tamper protection functionality by exhibiting unique physical fingerprint characteristics that automatically detect manipulation. No separate detection system is needed - the sheath's own physical response to test signals constitutes the security mechanism.

Inventive Principle:

Principle #25Self-service

2Reliability

If magnetic particles embedded in protective layer are used, then cryptographic key security is improved, but manufacturing complexity and cost increase

Engineering Contradiction:

Improvecryptographic key securityVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces complex manufacturing processes involving magnetic particle embedding with a simpler approach that uses standard sheath materials. The security is derived from measuring the sheath's natural physical properties rather than incorporating specialized magnetic particles during manufacturing.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

Instead of changing the material composition (adding magnetic particles), the patent changes the measurement parameters by applying test signals and analyzing the sheath's physical response characteristics such as signal attenuation, phase shift, and reflection properties.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If filigree grid film is used for tamper protection, then security against physical manipulation is improved, but ease of installation and maintenance deteriorates

Engineering Contradiction:

Improvesecurity against physical manipulationVSAvoidease of installation and maintenance

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent extracts the security functionality from separate components (grid films, stickers) and integrates it directly into the sheath structure itself. The sheath becomes the security element through its inherent physical properties, eliminating the need for separate installation and maintenance of security films.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent merges the protective sheath function with the tamper detection function into a single integrated structure. The sheath both protects the field device and provides the physical fingerprint for tamper detection, eliminating the need for separate grid films or security layers.

Inventive Principle:

Principle #5Merging (Combining)

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 simplifies tamper protection, enhances security with a high degree of reliability, reduces maintenance complexity, and eliminates the need for intricate grid films, providing both passive and active protection against physical manipulation.

Implementation Method 1

measurement of the first test signal in order to determine a physical fingerprint

Methodology Applied

Scientific EffectSignal attenuation: Absorption (EM radiation)

Implementation Method 2

measurement of the first test signal in order to determine a physical fingerprint

Methodology Applied

Scientific EffectPhase shift:

Implementation Method 3

measurement of the first test signal in order to determine a physical fingerprint

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS9959393B2Method for testing tamper protection of a field device and field device having tamper protection

Publication Date: 2018.05.01 SIEMENS AG

AI summary

Testing tamper protection of a field device includes arrangement of at least one test element in the material of a housing of the field device. The test element is supplied with a first test signal, and the first test signal is measured for determining a physical fingerprint. The physical fingerprint is measured, and the test element is supplied with a second test signal. The second test signal is measured, and the second test signal is compared with the physical fingerprint. If the second test signal deviates from the physical fingerprint, a tamper signal is output.