Directional Salt Derivation for Secure Uplink and Downlink Signaling

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Solution Overview

Problem

Existing wireless communication systems face security challenges in ensuring that salt values used for uplink and downlink transmissions between a terminal device and a P-CSCF are the same, leading to potential encryption and decryption failures.

Innovation Solution

A method where devices exchange information about their salt value calculation manners through messages, allowing them to determine the same salt values in uplink and downlink transmissions using specific parameters like port numbers, IP addresses, and security algorithms, ensuring distinct salt values for each direction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the same key, salt value, and initialization vector are used for both uplink and downlink transmissions, then the encryption and decryption processes become simpler, but security is compromised because the receiving end cannot correctly decrypt transmissions in either direction

Engineering Contradiction:
Improveencryption and decryption process complexityVSAvoidcommunication security
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The patent divides the salt value into two distinct parts: a first salt value for uplink transmissions and a second salt value for downlink transmissions. This segmentation allows each direction to use its own dedicated salt value, ensuring that encryption and decryption can proceed correctly without confusion, while maintaining the simplicity of the overall process.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent applies different salt values to different transmission directions (uplink vs. downlink). Each transmission direction receives a locally optimized salt value tailored to its specific needs, ensuring that the receiving end can correctly decrypt transmissions while maintaining overall system security.

Inventive Principle:
Principle #3Local quality

2Reliability

If different salt values are used for uplink and downlink transmissions, then communication security is improved, but the complexity of determining and managing salt values increases

Engineering Contradiction:
Improvecommunication securityVSAvoidsalt value management complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent determines the first and second salt values in advance during the authentication process, before actual uplink and downlink transmissions begin. This preliminary determination eliminates the need for complex real-time salt value management during transmission, as both ends already have the appropriate salt values ready for their respective directions.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The terminal device and network device autonomously determine their respective salt values based on pre-shared keys and direction-specific parameters without requiring additional coordination or complex management protocols. Each device independently generates and uses the appropriate salt value for its transmission direction.

Inventive Principle:
Principle #25Self-service

Data Source

PatentEP4697770A1Secure communication method and apparatus
Publication Date: 2026.02.18 HUAWEI TECH CO LTD
  • EP4697770A1 patent drawingFigure 1
  • EP4697770A1 patent drawingFigure 2~3
  • EP4697770A1 patent drawingFigure 4~6

AI summary

This application provides a secure communication method and apparatus. The method includes: A first device sends first information of the first device to a second device through a first message, where the first message includes one or more of a first port number, a first security parameter index SPI, a first internet protocol IP address, a first security algorithm list, and a first random number; the first device receives a second message that includes second information and that is from the second device, where the second message includes one or more of a second port number, a second SPI, a second IP address, a second security algorithm list, and a second random number; and based on the first information and/or the second information, the first device determines, in a first calculation manner, a first salt value used for uplink transmission between the first device and the second device, and/or determines, in a second calculation manner, a second salt value used for downlink transmission between the first device and the second device. This can ensure security of uplink and downlink communication between the first device and the second device.