Generation-Value Key Sharing for Resource-Limited Authentication Devices

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Solution Overview

Problem

Existing cryptographic technologies, such as public key infrastructure (PKI), face challenges with high processing load and risks of key leakage or illegal acquisition during key exchange, limiting their application to devices with large processing capabilities.

Innovation Solution

A key sharing method that utilizes a common key cryptosystem without PKI, where authentication devices and target devices share and generate distribution information using a generation value and encoding method to establish a common key, reducing the need for public key exchange and enhancing security.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If public key infrastructure is used for key exchange, then security is improved, but processing time increases and device complexity increases

Engineering Contradiction:

ImprovesecurityVSAvoidprocessing time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent divides the key exchange process into two independent phases: a key generation phase where each device independently generates a secret key and public key pair, and a key distribution phase where only the public keys are exchanged through communication channels. This segmentation allows security to be maintained while reducing processing time during the actual communication phase.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces public keys as intermediary elements that enable secure key distribution without direct exchange of secret keys. Each device's public key acts as a mediator, allowing the other device to encrypt information securely without requiring direct transmission of the secret key, thus improving security while reducing processing requirements.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If public key infrastructure is used for key exchange, then security is improved, but device complexity increases

Engineering Contradiction:

ImprovesecurityVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts the complex key exchange process from the communication phase and separates it into a preliminary key generation phase. By taking out the secret key exchange from the communication channel, the system reduces the complexity of devices needing to handle secure communications, as only public keys (which can be pre-installed or simply transmitted) are needed during actual communication.

Inventive Principle:

Principle #2Taking out (Extraction)

3Ease of operation

If common key is exchanged through communication channel, then key sharing is achieved, but risk of leakage or illegal acquisition increases

Engineering Contradiction:

Improvekey sharingVSAvoidkey leakage risk

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

Instead of exchanging the secret key directly through the communication channel (the conventional approach), the patent inverts the approach by having each device generate its own secret key independently and only exchange the non-sensitive public keys. The secret keys are never transmitted through the communication channel, eliminating the leakage risk while still enabling secure key sharing.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS12452043B2Key sharing method, key sharing system, authentication device, authentication target device, recording medium, and authentication method

Publication Date: 2025.10.21 DAI NIPPON PRINTING CO LTD

AI summary

A key sharing method between the authentication device and the authentication target device. The authentication device shares sharing information with the authentication target device in advance, one of the authentication device and the authentication target device shares a generation value generated by a predetermined method with the other of the authentication device and the authentication target device, and each of the authentication device and the authentication target device generates a plurality of pieces of first distribution information from the sharing information by using generation value with a predetermined encoding method capable of restoring data before distribution by arranging all or a part of a plurality of pieces of distribution data obtained by distributing the data before distribution, and shares one piece of first distribution information among the plurality of pieces of first distribution information or derivation information derived from the one piece of first distribution information as a common key.