Communication Terminal Message Key Reutilization for Server Load Reduction

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Solution Overview

Problem

In communication systems, particularly in real-time group chat systems, the server apparatus load increases due to the need for frequent processing and key updates, which is undesirable and can lead to performance issues.

Innovation Solution

Implementing a communication terminal that reutilizes a message key for encrypting messages by determining whether to newly generate or reuse a message key based on session key updates, and using a common key cryptosystem for re-encryption, allowing the server apparatus to reduce its processing load by storing and re-encrypting message keys efficiently without decrypting the message content.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the server apparatus frequently processes and updates session keys in real-time group chat systems, then communication security is maintained, but the server apparatus load increases

Engineering Contradiction:
Improvecommunication securityVSAvoidserver apparatus load
Core Design Contradiction:
ReliabilityVSProductivity

Solution Approach 1:

The invention segments the encryption key hierarchy into session keys (shared between communication terminals) and message keys (used for encrypting messages). This segmentation allows the server to manage only the message keys while communication terminals handle session key operations, reducing server processing load while maintaining security through the layered key structure.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The invention introduces message keys as intermediary elements between the session keys and the actual message content. Communication terminals encrypt messages with message keys, which are then encrypted with session keys before transmission to the server. This intermediary layer allows the server to store and re-encrypt message keys without needing to decrypt or process the actual message content, significantly reducing server processing requirements.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Reliability

If the server apparatus decrypts and processes message content to ensure security, then message verification is possible, but processing time increases

Engineering Contradiction:
Improvemessage verificationVSAvoidprocessing time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The invention extracts the decryption function from the server apparatus and places it in the communication terminals. Each terminal holds the session key needed to decrypt message keys, allowing terminals to verify message authenticity and decrypt content locally without requiring the server to perform time-consuming decryption operations. The server only stores encrypted message keys, eliminating the need for server-side decryption processing.

Inventive Principle:
Principle #2Taking out (Extraction)

3Reliability

If the server apparatus stores encrypted message keys for re-encryption, then message security is maintained, but storage and processing complexity increases

Engineering Contradiction:
Improvemessage securityVSAvoidstorage and processing complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The invention implements self-service by allowing communication terminals to perform re-encryption operations locally using their stored session keys. When a terminal receives an encrypted message key, it can decrypt and re-encrypt the message key with its current session key without server intervention. This eliminates the need for complex server-side re-encryption processing while maintaining security through the distributed key management approach.

Inventive Principle:
Principle #25Self-service

Data Source

PatentEP3709565B1Communication terminal, server device, and program
Publication Date: 2022.06.08 NIPPON TELEGRAPH & TELEPHONE CORP
  • EP3709565B1 patent drawingFigure 1
  • EP3709565B1 patent drawingFigure 2
  • EP3709565B1 patent drawingFigure 3

AI summary

A communication terminal which is capable of reducing load of a server apparatus by reutilizing a message key to be used for encrypting a message is provided. The communication terminal includes a session key storage part which stores a session key which is shared with another communication terminal and which is not shared with the server apparatus, a message key generating part which generates a message key, a message key storage part which stores the message key to be reutilized in association with a message key identifier, a message encrypting part which generates a message encrypted text based on a common key cryptosystem using the message and the message key, a message key encrypting part which generates a message key encrypted text based on a common key cryptosystem which can perform re-encryption using the session key and the message key, and an encrypted text transmitting part which transmits a group identifier which is an identifier of a group to which an own terminal belongs, the message key encrypted text or the message key identifier, and the message encrypted text to the server apparatus.