Multikey Homomorphic Encryption for Searchable Data Privacy

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Solution Overview

Problem

Conventional searchable encryption schemes leak search patterns, compromising user privacy and allowing servers to infer personal information from search queries, while also being vulnerable to quantum attacks and requiring client-server interaction for query formulation.

Innovation Solution

A method using multikey homomorphic encryption generates distinct key triples for each searchable information and file, merging secret keys to provide encrypted data, and employs a non-interactive proof scheme to ensure privacy and security, allowing efficient search operations without revealing query patterns or requiring client interaction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of information

If conventional searchable encryption schemes are used, then data privacy is protected, but search patterns are leaked to the server

Engineering Contradiction:
Improvesearch pattern privacyVSAvoiddata encryption security
Core Design Contradiction:
Loss of informationVSReliability

Solution Approach 1:

The patent segments the search process into distinct phases: the client generates search tokens locally without revealing the actual search terms to the server. The server only receives encrypted search tokens and encrypted database records, never seeing the plaintext search patterns. This segmentation isolates the privacy-sensitive operations on the client side while allowing the server to perform encrypted matching operations.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent introduces encrypted search tokens as an intermediary between the user's search intent and the server's database. These tokens act as a mediator that carries the search functionality without exposing the underlying search pattern. The server operates on these intermediate encrypted representations rather than directly on the user's search queries.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Ease of operation

If searchable encryption is implemented, then users can search encrypted data, but client-server interaction is required for query formulation

Engineering Contradiction:
Improvesearch functionalityVSAvoidclient-server interaction protocol
Core Design Contradiction:
Ease of operationVSDevice complexity

Solution Approach 1:

The patent implements preliminary action by having the client generate all necessary search tokens and encrypt all database records beforehand. The server receives pre-processed encrypted data structures that enable it to perform search operations autonomously without requiring interactive query formulation with the client. The search capability is prepared in advance through local client-side token generation.

Inventive Principle:
Principle #10Preliminary action

3Reliability

If conventional encryption is used, then data is secured, but searching on encrypted data is impossible

Engineering Contradiction:
Improvedata securityVSAvoidsearch capability
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The patent changes the parameter of encryption from traditional semantic security to searchable encryption by modifying the encryption scheme to support homomorphic operations. This allows the encrypted data to maintain security properties while enabling mathematical operations on the ciphertexts that can reveal search results without decryption. The encryption parameters are adjusted to permit controlled information leakage only about search outcomes.

Inventive Principle:
Principle #35Parameter changes

4Ease of operation

If searchable encryption schemes are deployed, then search functionality is enabled, but they are vulnerable to quantum attacks

Engineering Contradiction:
Improvesearch capabilityVSAvoidquantum security
Core Design Contradiction:
Ease of operationVSReliability

Solution Approach 1:

The patent employs quantum-resistant cryptographic primitives that are designed to be computationally inexpensive and can be easily regenerated. The system uses post-quantum encryption schemes that do not rely on mathematical problems vulnerable to quantum attacks, such as lattice-based cryptography. These cryptographic objects can be disposed of and regenerated if security concerns arise, providing a practical defense against quantum threats.

Inventive Principle:
Principle #27Cheap short-living objects (Disposable)

Data Source

PatentEP2951945B1Method and system for providing encrypted data for searching of information therein and a method and system for searching of information on encrypted data
Publication Date: 2020.09.09 NEC CORP
  • EP2951945B1 patent drawingFigure 1
  • EP2951945B1 patent drawing

AI summary

The present invention relates to a method for providing encrypted data for searching of information therein, comprising the steps of a) Generating a number of distinct key triples each comprising a public key, a corresponding secret key and a corresponding evaluation key being dependent on one or more searchable information and being dependent on one or more files on which a search may be performed, b) Encrypting the information indicating whether or not the one or more searchable information is included in one or more of the files with a key of the generated key triples, c) Merging the one or more secret keys to obtain a single secret key for all searchable information within a file for each file and d) Providing the encrypted information with the merged secret keys for each file as encrypted data for searching of information therein, wherein at least steps a)-b) are based on a multikey homomorphic encryption scheme. The present invention further relates to a method of information on encrypted data, a system for providing encrypted data for searching of information therein and a system of searching of information on encrypted data.