Zero-Knowledge Proof Electronic Signature Generation

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Solution Overview

Problem

Current electronic signature methods require document issuers to either share confidential documents with service providers or possess specific skills and computing power, compromising security and reliability, especially when sensitive information is involved.

Innovation Solution

A method using zero-knowledge proofs, specifically zkSNARKs, allows a server to generate an electronic signature for a document without accessing the original document, ensuring confidentiality and security by verifying that the hash provided is indeed linked to a valid document possessed by the client, using cryptographic hash functions like SHA-1 or SHA-2 and the Merkle-Damgård principle.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the document is transmitted in plain text to the FSS for signature generation, then the FSS can verify the document and generate a valid signature, but the confidentiality of the document is compromised

Engineering Contradiction:
Improvesignature validityVSAvoiddocument confidentiality
Core Design Contradiction:
ReliabilityVSLoss of information

Solution Approach 1:

A zero-knowledge proof acts as an intermediary mechanism between the document hash and the FSS. The proof verifies that the hash corresponds to a valid document without revealing the document content itself, allowing the FSS to confirm authenticity while maintaining confidentiality.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention extracts only the essential verification element (zero-knowledge proof) from the complete document, allowing the FSS to verify signature validity without accessing the actual document content, thus separating verification needs from confidential information.

Inventive Principle:
Principle #2Taking out (Extraction)

2Loss of information

If only the document hash is transmitted to the FSS, then document confidentiality is maintained, but the FSS cannot verify that the hash corresponds to a valid document

Engineering Contradiction:
Improvedocument confidentialityVSAvoidsignature validity
Core Design Contradiction:
Loss of informationVSReliability

Solution Approach 1:

The zero-knowledge proof serves as a mediator that bridges the gap between hash transmission and verification. It provides the FSS with sufficient information to verify document validity without requiring access to the document itself, enabling confidence in signature legitimacy while maintaining confidentiality.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The zero-knowledge proof is generated in advance by the document issuer before transmitting the hash to the FSS. This preliminary verification mechanism ensures that when the FSS receives the hash, it already has cryptographic evidence that the hash corresponds to a valid document, eliminating the need for the FSS to access the original document.

Inventive Principle:
Principle #10Preliminary action

3Loss of information

If the client generates the signature themselves, then document confidentiality is maintained, but specific skills, certification, and computing power are required

Engineering Contradiction:
Improvedocument confidentialityVSAvoidsignature generation capability
Core Design Contradiction:
Loss of informationVSDevice complexity

Solution Approach 1:

The zero-knowledge proof mechanism acts as an intermediary that enables clients without cryptographic expertise to securely delegate signature generation. The proof system handles the complexity of verification, allowing the FSS to generate signatures using standard procedures while the client maintains confidentiality through the proof mechanism.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The system enables self-service signature generation where the client prepares the zero-knowledge proof and hash, then the FSS automatically verifies and generates the signature using standard cryptographic operations. This eliminates the need for the client to possess specialized signature generation skills while maintaining security.

Inventive Principle:
Principle #25Self-service

Data Source

PatentEP3334121B1Process of generating an electronic signature of a document associated to a digest
Publication Date: 2023.07.26 IDEMIA IDENTITY & SECURITY FRANCE SAS
  • EP3334121B1 patent drawingFigure 1
  • EP3334121B1 patent drawingFigure 2
  • EP3334121B1 patent drawing

AI summary

The present invention relates to a method for generating an electronic signature of a document associated with a hash obtained by a given hash function, comprising the implementation by data processing means (11b) of a server (1b) of the steps of: (a) Receiving said hash and a zero-knowledge proof that said hash is indeed the result of applying said given hash function to said document; (b) Verifying that said zero-knowledge proof is valid; (c) generating an electronic signature of the document from said hash.