Dynamic Encrypted Subscriber Identity for TETRA Privacy

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Solution Overview

Problem

In Terrestrial Trunked Radio Access (TETRA) networks, the static nature of encrypted subscriber identities over the air interface allows for potential tracking of user terminals, compromising location privacy, as the same encrypted identity is used within a location area or the entire network.

Innovation Solution

A method and apparatus that generate and use temporary or modified encrypted subscriber identities, which change dynamically based on parameters like cipher keys and location-specific information, ensuring that only authorized users can identify messages intended for them, thereby enhancing privacy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a static encrypted identity is used over the air interface, then the implementation is simple and backward compatible, but the location privacy of user terminals is compromised and tracking becomes possible

Engineering Contradiction:
Improveidentity management complexityVSAvoidlocation privacy loss
Core Design Contradiction:
Device complexityVSObject-affected harmful factors

Solution Approach 1:

The patent applies dynamics by transitioning from a static encrypted identity to a dynamic temporary encrypted identity that changes over time. The temporary encrypted identity is generated by modifying the original encrypted identity using a modification value derived from current time or frame numbers, ensuring the identity evolves continuously to prevent tracking while maintaining system simplicity

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of the encrypted identity by introducing a modification value that alters the original encrypted identity. This modification value is generated based on time or frame number parameters, transforming the static identity into a time-varying identity that maintains privacy protection without significantly increasing system complexity

Inventive Principle:
Principle #35Parameter changes

2Object-affected harmful factors

If a dynamic temporary encrypted identity is generated and used, then location privacy is enhanced and tracking is prevented, but the system complexity increases

Engineering Contradiction:
Improvelocation privacy protectionVSAvoididentity management complexity
Core Design Contradiction:
Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The system implements dynamics by making the encrypted identity time-varying through the use of temporary encrypted identities. These identities are generated by applying a modification value to the original encrypted identity, where the modification value changes with time or frame numbers, thereby enhancing privacy while using a systematic approach to manage the increased complexity

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent manages complexity by systematically changing identity parameters through controlled modification. The temporary encrypted identity is derived from the original encrypted identity using a modification value based on time or frame numbers, providing a structured method to enhance privacy without arbitrary complexity increases

Inventive Principle:
Principle #35Parameter changes

3Object-affected harmful factors

If the encrypted identity changes frequently, then tracking difficulty increases and privacy is improved, but the stability of identity recognition may be affected

Engineering Contradiction:
Improvetracking difficultyVSAvoididentity stability
Core Design Contradiction:
Object-affected harmful factorsVSStability of the object's composition

Solution Approach 1:

The patent resolves the stability conflict by implementing controlled dynamics. The temporary encrypted identity changes over time through modification values derived from time or frame numbers, making tracking difficult while maintaining a systematic structure that ensures proper identity recognition and network functionality

Inventive Principle:
Principle #15Dynamics

4Object-affected harmful factors

If a modified encrypted identity scheme is implemented, then location privacy is enhanced, but compatibility with legacy systems may be compromised

Engineering Contradiction:
Improvelocation privacy protectionVSAvoidbackward compatibility
Core Design Contradiction:
Object-affected harmful factorsVSAdaptability or versatility

Solution Approach 1:

The patent uses an intermediary approach by introducing a temporary encrypted identity that serves as a bridge between the original encrypted identity and the privacy-enhanced requirement. The modification value acts as an intermediary element that transforms the original identity into a protective form while maintaining the underlying structure that legacy systems can recognize and process

Inventive Principle:
Principle #24Intermediary (Mediator)

Data Source

PatentEP2782315B1Mechanism to obtain an modified encrypted subscriber identity in tetra
Publication Date: 2017.07.19 AIRBUS DEFENCE & SPACE OY
  • EP2782315B1 patent drawingFigure 1~3
  • EP2782315B1 patent drawingFigure 4A~4C
  • EP2782315B1 patent drawingFigure 4D~4E

AI summary

To provide encrypted identities with a more dynamic nature, an encrypted identity is modified by an algorithm using the encrypted identity and one or more parameter values as inputs of the algorithm, the algorithm outputting a modified encrypted identity that is used in information transmitted over an air interface.