Passive Keyless Entry Relay Detection Using Timestamp Hash Checks

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Solution Overview

Problem

Passive keyless entry (PKE) systems are vulnerable to relay and replay attacks, which allow attackers to deceive the vehicle into thinking the smart key is present, leading to unauthorized access and theft.

Innovation Solution

The method involves generating and transmitting a first signal with a random number and timestamp to the smart key, receiving a second signal with a hash value and timestamp, and comparing the timestamp differences to determine if a relay or replay attack is occurring, thereby preventing unauthorized access.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If timestamp comparison method is implemented to detect relay/replay attacks, then system security is improved, but communication overhead and processing time increase

Engineering Contradiction:
Improvesystem securityVSAvoidprocessing time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The patent applies preliminary action by pre-generating and embedding timestamp values in the first signal before transmission to the smart key. This allows the timestamp comparison to be performed efficiently during the authentication process without requiring complex real-time calculations, thus improving security while minimizing additional processing time.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent replaces complex cryptographic verification mechanisms with a simpler timestamp comparison mechanism. Instead of relying solely on computationally intensive encryption/decryption processes, the system uses temporal information (timestamps) to detect relay and replay attacks, reducing processing overhead while maintaining security.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If random number and timestamp are included in authentication signals, then attack detection capability is improved, but signal complexity and data transmission overhead increase

Engineering Contradiction:
Improveattack detection capabilityVSAvoidsignal complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent changes the parameters of the authentication signal by incorporating timestamp values and random numbers. These parameter additions enable the system to detect relay and replay attacks by comparing temporal and random elements, thereby improving attack detection capability while maintaining manageable signal complexity through structured data formats.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentEP4549260A1Apparatus and method for distinguishing relay/replay signal in passive keyless entry system
Publication Date: 2025.05.07 HYUNDAI MOTOR CO LTD
  • EP4549260A1 patent drawingFigure 1A
  • EP4549260A1 patent drawingFigure 1B
  • EP4549260A1 patent drawingFigure 1C

AI summary

A method of operating a passive keyless entry (PKE) system of a vehicle can include generating and transmitting to a smart key, a first signal including a first random number and a first timestamp value, receiving from the smart key, a second signal including a second hash value and a second timestamp value, generating a third timestamp value, comparing a first difference between the second timestamp value and the first timestamp value with a first threshold for determining whether a relay signal has occurred, comparing a second difference between the third timestamp value and the second timestamp value with a second threshold for determining whether a relay signal and/or a replay signal has occurred, and comparing a first hash value based on the first timestamp value with the second hash value to determine whether to allow access to and start up of the vehicle.