Proxy Re-Encryption Matching System for Secure Homomorphic Operations

Solution Overview

Problem

Homomorphic operations between ciphertexts encrypted with different public keys are not executed correctly, and encrypting data with all user public keys in a brute-force manner increases the time plaintexts are exposed, making the system vulnerable to attacks.

Innovation Solution

A matching system using proxy re-encryption to convert ciphertexts from a service public key to a user public key without decryption, enabling secure and efficient homomorphic operations between ciphertexts with different keys.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If ciphertexts are encrypted with different public keys to ensure security, then security is improved, but homomorphic operations cannot be executed correctly

Engineering Contradiction:

ImprovesecurityVSAvoidhomomorphic operation execution

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent introduces a key conversion mechanism that acts as an intermediary between ciphertexts encrypted with different public keys. The key conversion unit converts the first ciphertext (encrypted with service public key) into a second ciphertext (encrypted with user public key) using a conversion key, enabling homomorphic operations between ciphertexts that were originally encrypted with different keys while maintaining security

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If data is encrypted with all user public keys in a brute-force manner to enable matching, then matching capability is improved, but the time plaintexts are exposed increases making the system vulnerable to attacks

Engineering Contradiction:

Improvematching capabilityVSAvoidplaintext exposure time

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The patent performs key conversion in advance before the matching process. The conversion key is generated beforehand, and the first ciphertext is converted to the second ciphertext before homomorphic matching operations are performed. This preliminary action eliminates the need for brute-force encryption with all user public keys, significantly reducing the time plaintexts are exposed while maintaining matching capability

Inventive Principle:

Principle #10Preliminary action

3Reliability

If proxy re-encryption is used to convert ciphertexts without decryption, then security is improved, but device complexity increases

Engineering Contradiction:

ImprovesecurityVSAvoidsystem complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent introduces a key conversion mechanism that acts as an intermediary between ciphertexts encrypted with different public keys. The key conversion unit converts the first ciphertext (encrypted with service public key) into a second ciphertext (encrypted with user public key) using a conversion key, enabling homomorphic operations between ciphertexts that were originally encrypted with different keys while maintaining security

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS20250211439A1Matching system, matching apparatus, matching method, and program

Publication Date: 2025.06.26 NEC CORP

AI summary

A (secure) matching system includes a user-side apparatus; and a service-side apparatus. The user-side apparatus includes a user key generation part and a registration part that registers a registration ciphertext in the service-side apparatus. The service-side apparatus includes a service key generation part, a conversion key generation part that generates a conversion key for converting a first ciphertext encrypted with a service public key into a second ciphertext encrypted with a user public key without executing a decryption process, and a matching part. The service-side apparatus generates a second ciphertext with the conversion key after generating a first ciphertext obtained by encrypting features used as a matching source with the service public key and matches the second ciphertext against a registered ciphertext.