Source Authentication via Decryption Key Error Analysis

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Solution Overview

Problem

In power line communication networks, distinguishing the source of data communications is challenging due to overlapping channels, leading to potential misidentification of signals from neighboring endpoints, which can result in improper logging of data.

Innovation Solution

Assigning unique encryption and decryption keys to each endpoint, allowing the substation processing unit to determine the source of communications based on the decryption key that properly decrypts the data, and using error correction techniques to identify valid symbols and discard interfering signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If endpoints in neighboring PLC networks communicate over the same or nearby channels, then network coverage and channel utilization are improved, but signal interference and source identification accuracy deteriorate

Engineering Contradiction:
Improvenetwork coverageVSAvoidsource identification accuracy
Core Design Contradiction:
Area of stationary objectVSMeasurement precision

Solution Approach 1:

The patent segments the identification process by assigning unique decryption keys to each endpoint. Instead of relying solely on channel-based identification which fails under overlap, each endpoint is given a unique cryptographic identifier that segments the source identification space, allowing precise differentiation even when channels overlap.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent introduces decryption keys as an intermediary mechanism for source identification. Rather than directly identifying sources through channel analysis (which fails under interference), the system uses decryption keys as a mediator that enables accurate source identification by verifying which key successfully decrypts the received signal.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Measurement precision

If encryption keys are assigned to each endpoint for source identification, then source authentication accuracy is improved, but system complexity and key management overhead increase

Engineering Contradiction:
Improvesource authentication accuracyVSAvoidkey management complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent makes the decryption key serve multiple functions: it acts as both an authentication credential for source identification and as an error detection mechanism through CRC verification. This multi-functionality reduces the need for separate identification protocols, thereby limiting the increase in system complexity.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system implements self-service through automatic key testing and CRC verification. The receiving endpoint automatically tests which decryption key successfully decrypts the signal and verifies integrity through CRC, eliminating the need for manual source identification or complex external authentication protocols.

Inventive Principle:
Principle #25Self-service

3Reliability

If CRC verification is performed on encrypted messages, then error detection capability is improved, but processing time and computational overhead increase

Engineering Contradiction:
Improveerror detection capabilityVSAvoidprocessing time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The patent performs preliminary CRC calculation on the plaintext message before encryption. This preliminary action allows the CRC to be prepared in advance, so that during reception, the system only needs to decrypt and compare rather than perform full verification from scratch, reducing processing time while maintaining error detection capability.

Inventive Principle:
Principle #10Preliminary action

Data Source

PatentEP2622787B1Communications source authentication
Publication Date: 2019.08.28 LANDIS & GYR TECHNOLOGIES LLC
  • EP2622787B1 patent drawingFigure 1
  • EP2622787B1 patent drawingFigure 2
  • EP2622787B1 patent drawingFigure 3

AI summary

Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for authenticating a communications source. In one aspect, a method includes decrypting a symbol that was received over a particular communications channel. The symbol is decrypted using a decryption key that is assigned to a particular endpoint that is assigned the particular communications channel. A measure of error is computed for the decrypted symbol. In turn, a determination is made whether the measure of error exceeds a threshold error measure. If the measure of error does not exceed the threshold error measure the decrypted symbol is identified as a valid symbol transmitted by the particular endpoint, and logged as such. If the measure of error exceeds the threshold error measure, the decrypted symbol is identified as a symbol from a different endpoint.