Zero-knowledge proof-based electronic invoice credit voucher generation and verification method and system

Abstract

The invention discloses an electronic invoice credit voucher generation and verification method and system based on zero knowledge certification, and the method comprises the steps: receiving a certification request sent by an enterprise through an invoicing platform based on a block chain; according to the certification request, obtaining encrypted electronic transmission sub-invoice information of the enterprise; generating a total turnover and a total gross profit of the enterprise according to input and output items in the electronic invoice information; generating zero-knowledge proof of the enterprise according to private input in the electronic invoice information and public input set by a financial institution; and submitting the zero-knowledge proof of the enterprise to a financial institution as an electronic invoice credit voucher. On the premise that specific invoice information of an enterprise is not disclosed, it is ensured that a financial institution can trust financial proof provided by the enterprise.

Description

Technical Field

[0001] The present invention relates to the technical field of data security, and particularly to a method and system for generating and verifying electronic invoice credit vouchers based on zero-knowledge proof. Background Art

[0002] With the application and popularization of electronic invoices globally, it has become a common business practice for enterprises to record purchase and sales transactions and conduct financial management through invoices. The turnover and profit levels of enterprises can be accurately calculated through invoice data, which is crucial for scenarios such as financing and credit assessment. However, when an enterprise needs to provide financial data to a financial institution as a credit voucher, directly exposing specific invoice information has the following problems:

[0003] 1. Data privacy: The invoice data of an enterprise contains sensitive transaction details, such as transaction party information, transaction amount, goods details, etc. The public disclosure of this data may expose the enterprise's trade secrets and even affect its market competitiveness. Therefore, how to protect the privacy of enterprises while providing credible financial data has become an urgent problem to be solved.

[0004] 2. Data security: Once invoice data is exposed or tampered with, it may cause serious commercial losses to the enterprise and its partners. In recent years, blockchain technology has been widely applied to invoice management to protect the authenticity and integrity of data through its immutable characteristics.

[0005] 3. Third-party verification requirements: Financial institutions usually need to verify the turnover and profit levels of enterprises to evaluate their creditworthiness. However, traditional financial auditing methods are inefficient and cannot protect the privacy of enterprises. The introduction of zero-knowledge proof technology enables enterprises to prove that their financial status meets the standards without disclosing specific transaction data, thus meeting the requirements of financial institutions for credit vouchers.

[0006] Currently, zero-knowledge proof technology has been widely applied in the fields of privacy protection and data verification. It provides an effective mechanism that can generate verifiable mathematical proofs without revealing specific data. Under this mechanism, the verifier can ensure that the proof provided by the enterprise is true and does not need to know the specific invoice content.

[0007] Blockchain technology has also been applied in invoice management. By encrypting and storing enterprise invoices on the blockchain, the security and immutability of the data are ensured. Combining zero-knowledge proof technology, enterprises can use the encrypted invoice data to generate financial proofs to meet the credit assessment requirements of financial institutions without leaking sensitive information.

[0008] In existing solutions, most only encrypt invoice data and store it on the blockchain. Although the data has privacy protection, how to prove the financial status of an enterprise to a third party still relies on traditional auditing methods, lacking efficient and privacy-friendly means. How to combine zero-knowledge proofs with blockchain to solve the above problems has become a key direction in the current technological development. Summary of the Invention

[0009] In view of the above technical problems, the present invention provides a method and system for generating and verifying electronic invoice credit vouchers based on zero-knowledge proofs. The generation method includes:

[0010] A blockchain-based invoicing platform receives a proof request sent by an enterprise;

[0011] According to the proof request, encrypted electronic invoice information of the enterprise is obtained;

[0012] Based on the input and output items in the electronic invoice information, the total turnover and total gross profit of the enterprise are generated; based on the private input in the electronic invoice information and the public input set by the financial institution, a zero-knowledge proof of the enterprise is generated;

[0013] The zero-knowledge proof of the enterprise is submitted to the financial institution as an electronic invoice credit voucher.

[0014] Further, generating the zero-knowledge proof of the enterprise based on the private input in the electronic invoice information and the public input set by the financial institution includes:

[0015] Based on the input invoice amount and output invoice amount in the electronic invoice information, a zero-knowledge proof of the enterprise is generated through the Groth16 protocol.

[0016] Further, generating the total turnover and total gross profit of the enterprise based on the input and output items in the electronic invoice information includes:

[0017] The output invoice amounts in the electronic invoice information are added up to obtain the total turnover of the enterprise;

[0018] The total turnover in the electronic invoice information is subtracted by the total input invoice amount to obtain the total gross profit of the enterprise.

[0019] The present invention also provides a method for verifying an electronic invoice credit voucher based on zero-knowledge proofs, including:

[0020] The financial institution receives the electronic invoice credit voucher submitted by the enterprise;

[0021] Verify the validity of the zero-knowledge proof in the electronic invoice credit voucher, and whether the total turnover and total gross profit in the electronic invoice credit voucher meet the requirements of financial institutions;

[0022] When the zero-knowledge proof is verified as valid and the total turnover and total gross profit in the electronic invoice credit voucher meet the requirements of financial institutions, the verification of the enterprise's electronic invoice credit voucher passes.

[0023] Furthermore, verifying the validity of the zero-knowledge proof in the electronic invoice credit voucher includes:

[0024] Determine that the zero-knowledge proof in the electronic invoice credit voucher is within the validity period through the verification algorithm of Groth16, then the zero-knowledge proof is valid.

[0025] Furthermore, verifying whether the total turnover and total gross profit in the electronic invoice credit voucher meet the requirements of financial institutions includes:

[0026] If the total turnover is greater than the first threshold set by the financial institution and the total gross profit is greater than the second threshold set by the financial institution, then the total turnover and total gross profit in the electronic invoice credit voucher meet the requirements of financial institutions.

[0027] The present invention also provides an electronic invoice credit voucher generation system based on zero-knowledge proof, including:

[0028] A proof request receiving module, configured to receive a proof request sent by an enterprise based on a blockchain-based invoicing platform;

[0029] An invoice information acquisition module, configured to acquire the encrypted electronic invoice information of the enterprise according to the proof request;

[0030] A proof generation module, configured to generate the total turnover and total gross profit of the enterprise according to the input tax and output tax in the electronic invoice information; generate the zero-knowledge proof of the enterprise according to the private input in the electronic invoice information and the public input set by the financial institution;

[0031] A credit voucher return module, configured to submit the zero-knowledge proof of the enterprise to the financial institution as an electronic invoice credit voucher.

[0032] Furthermore, the proof generation module includes:

[0033] A proof generation sub-module, configured to generate the zero-knowledge proof of the enterprise through the Groth16 protocol according to the input tax invoice amount and output tax invoice amount in the electronic invoice information.

[0034] The present invention also provides an electronic invoice credit voucher verification system based on zero-knowledge proof, including:

[0035] A credit voucher receiving module for a financial institution to receive electronic invoice credit vouchers submitted by an enterprise;

[0036] A first verification module for verifying the validity of the zero - knowledge proof in the electronic invoice credit voucher, and whether the total turnover and total gross profit in the electronic invoice credit voucher meet the requirements of the financial institution;

[0037] A second verification module for, when the zero - knowledge proof is verified as valid and the total turnover and total gross profit in the electronic invoice credit voucher meet the requirements of the financial institution, the electronic invoice credit voucher of the enterprise is verified as passed.

[0038] Furthermore, the first verification module includes:

[0039] A zero - knowledge proof verification sub - module for determining that the zero - knowledge proof in the electronic invoice credit voucher is valid within the validity period through the verification algorithm of Groth16.

[0040] A method and system for generating and verifying electronic invoice credit vouchers based on zero - knowledge proof provided by the present invention ensure that a financial institution can trust the financial proof provided by an enterprise without disclosing the specific invoice information of the enterprise. Through the Groth16 protocol, the financial institution can quickly verify the proof of the enterprise, reducing the complexity of data processing and auditing, and at the same time ensuring the credibility of the information submitted by the enterprise. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a schematic flow chart of a method for generating an electronic invoice credit voucher based on zero - knowledge proof provided by an embodiment of the present invention;

[0042] Figure 2 is a schematic flow chart of a method for verifying an electronic invoice credit voucher based on zero - knowledge proof provided by an embodiment of the present invention;

[0043] Figure 3 is a schematic structural diagram of a system for generating an electronic invoice credit voucher based on zero - knowledge proof provided by an embodiment of the present invention;

[0044] Figure 4 is a schematic structural diagram of a system for verifying an electronic invoice credit voucher based on zero - knowledge proof provided by an embodiment of the present invention;

[0045] Figure 5 is the overall process of generating and verifying invoice credit vouchers related to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0046] Many specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present invention, so the present invention is not limited to the specific implementation disclosed below.

[0047] The present invention proposes a method for generating and verifying electronic invoice credit vouchers based on zero-knowledge proof, which stores the encrypted invoice information of enterprises through blockchain, and uses zero-knowledge proof to verify whether the enterprises meet the turnover and gross profit requirements set by financial institutions. The invoices are encrypted and stored on the chain, and the invoicing platform has all the invoice data of the enterprise, and assists the enterprise in generating zero-knowledge proofs to prove that the enterprise's turnover and gross profit meet the standards. The present invention provides a method for generating electronic invoice credit vouchers based on zero-knowledge proof, such as Figure 1 As shown, the following steps are included:

[0048] Step S101, the blockchain-based invoicing platform receives a certification request sent by the enterprise.

[0049] The main roles involved in this invention are:

[0050] Enterprise (Prover): The enterprise has all the invoice data and knows its actual turnover and gross profit. The enterprise needs to generate zero-knowledge proof to provide credit credentials to financial institutions.

[0051] Invoicing platform: The blockchain-based invoicing platform is responsible for the encrypted storage and management of the company's invoice data. The platform has all the company's purchase and sales invoice data and assists the company in generating zero-knowledge proofs.

[0052] Financial Institutions (Verifier): Financial institutions need to verify whether a company's turnover and gross profit meet a certain threshold, but do not want or need to see the company's detailed invoice data.

[0053] When an enterprise needs to prove its financial status to a financial institution, it initiates a proof request through the invoicing platform. The proof includes whether the enterprise's turnover and gross profit meet the thresholds set by the financial institution, such as turnover greater than 10 million yuan and gross profit greater than 2 million yuan. The enterprise calls the encrypted invoice data stored on the platform.

[0054] The present invention firstly receives the certification request sent by the enterprise through the invoicing platform, and then generates an electronic invoice credit certificate through the invoicing platform.

[0055] Step S102: Obtain the encrypted electronic invoice information of the enterprise according to the certification request.

[0056] The enterprise issues all invoices (including input invoices and output invoices) through the invoicing platform, and the platform encrypts and stores this invoice data on the blockchain. Each piece of invoice data, including the invoice number, amount, trading parties, etc., is encrypted and stored in the blockchain to ensure its immutability and high privacy.

[0057] Step S103, generate the total turnover and total gross profit of the enterprise according to the input and output in the electronic invoice information; generate the zero-knowledge proof of the enterprise according to the private input in the electronic invoice information and the public input set by the financial institution.

[0058] The private income includes two parts, namely the list of input invoice amounts of the enterprise, representing the procurement data of the enterprise, and the list of output invoice amounts of the enterprise, representing the sales data of the enterprise. The public input also includes two parts, namely the turnover threshold set by the financial institution, such as 10 million yuan, and the gross profit threshold set by the financial institution, such as 2 million yuan.

[0059] Generate the zero-knowledge proof of the enterprise through the Groth16 protocol according to the input invoice amount and output invoice amount in the electronic invoice information.

[0060] Add up the output invoice amounts in the electronic invoice information to obtain the total turnover of the enterprise;

[0061] Subtract the total amount of input invoices from the total turnover in the electronic invoice information to obtain the total gross profit of the enterprise.

[0062] Step S104, submit the zero-knowledge proof of the enterprise as an electronic invoice credit voucher to the financial institution.

[0063] The Groth16 protocol generates a zero-knowledge proof, which can be verified by the financial institution but does not contain specific invoice data. Finally, return the zero-knowledge proof, total turnover and total gross profit of the enterprise as an electronic invoice credit voucher to the enterprise.

[0064] Based on the same inventive concept, the present invention also provides an electronic invoice credit voucher verification method based on zero-knowledge proof, and its process is as Figure 2 shown, including the following steps:

[0065] Step S201, the financial institution receives the electronic invoice credit voucher submitted by the enterprise.

[0066] Step S202, verify the validity of the zero-knowledge proof in the electronic invoice credit voucher, and whether the total turnover and total gross profit in the electronic invoice credit voucher meet the requirements of the financial institution.

[0067] The electronic invoice credit voucher is verified by a financial institution. The financial institution first uses the verification algorithm of Groth16 to determine that the zero-knowledge proof in the electronic invoice credit voucher is within the validity period, then the zero-knowledge proof is valid. If it is not within the validity period, the zero-knowledge proof is invalid. Then, it verifies whether the total turnover and the total gross profit meet the requirements of the financial institution respectively, specifically including: if the total turnover is greater than the first threshold set by the financial institution and the total gross profit is greater than the second threshold set by the financial institution, then the total turnover and the total gross profit in the electronic invoice credit voucher meet the requirements of the financial institution.

[0068] Step S203, when the zero-knowledge proof is verified as valid and the total turnover and the total gross profit in the electronic invoice credit voucher meet the requirements of the financial institution, then the verification of the enterprise's electronic invoice credit voucher passes.

[0069] If one or more of the zero-knowledge proof, the total turnover, and the total gross profit in the electronic invoice credit voucher do not meet the requirements in the verification, then the verification of the enterprise's electronic invoice credit voucher fails.

[0070] Based on the same inventive concept, the present invention also provides an electronic invoice credit voucher generation system 300 based on zero-knowledge proof, as Figure 3 shown, including:

[0071] A proof request receiving module 310, configured to receive a proof request sent by an enterprise based on a blockchain-based invoicing platform;

[0072] An invoice information acquisition module 320, configured to acquire the encrypted electronic invoice information of the enterprise according to the proof request;

[0073] A proof generation module 30, configured to generate the total turnover and the total gross profit of the enterprise according to the input tax and output tax in the electronic invoice information; and generate the zero-knowledge proof of the enterprise according to the private input in the electronic invoice information and the public input set by the financial institution;

[0074] A credit voucher return module 340, configured to submit the zero-knowledge proof of the enterprise to the financial institution as an electronic invoice credit voucher.

[0075] Further, the proof generation module includes:

[0076] A proof generation sub-module, configured to generate the zero-knowledge proof of the enterprise through the Groth16 protocol according to the input invoice amount and the output invoice amount in the electronic invoice information.

[0077] The present invention also provides an electronic invoice credit voucher verification system 400 based on zero-knowledge proof, as Figure 4 shown, including:

[0078] A credit voucher receiving module 410, which is used for a financial institution to receive the electronic invoice credit vouchers submitted by an enterprise;

[0079] A first verification module 420, which is used to verify the validity of the zero - knowledge proof in the electronic invoice credit voucher, and whether the total turnover and total gross profit in the electronic invoice credit voucher meet the requirements of the financial institution;

[0080] A second verification module 430, which is used to determine that the electronic invoice credit voucher of the enterprise passes the verification when the zero - knowledge proof is verified as valid and the total turnover and total gross profit in the electronic invoice credit voucher meet the requirements of the financial institution.

[0081] Furthermore, the first verification module includes:

[0082] A zero - knowledge proof verification sub - module, which is used to determine that the zero - knowledge proof in the electronic invoice credit voucher is valid by using the verification algorithm of Groth16 within the validity period.

[0083] The working process of the invoice credit voucher generation and verification of the present invention is as Figure 5 shown, specifically as follows:

[0084] (1) Invoice encrypted storage

[0085] The enterprise issues all invoices (including input invoices and output invoices) through the invoicing platform, and the platform encrypts these invoice data and stores them on the blockchain. Each piece of invoice data, including invoice number, amount, trading party, etc., is encrypted and then stored in the blockchain to ensure its immutability and high privacy.

[0086] (2) The enterprise initiates a proof request

[0087] When the enterprise needs to prove its financial status to the financial institution, the enterprise initiates a proof request through the invoicing platform. The proof content includes whether the turnover and gross profit of the enterprise meet the thresholds set by the financial institution, for example, the turnover is greater than 10 million yuan and the gross profit is greater than 2 million yuan. The enterprise calls the encrypted invoice data stored by the platform.

[0088] (3) Groth16 zero - knowledge proof circuit design

[0089] Private inputs (Witnesses): The list of input invoice amounts of the enterprise, representing the procurement data of the enterprise; the list of output invoice amounts of the enterprise, representing the sales data of the enterprise.

[0090] Public inputs (Public Inputs): The turnover threshold set by the financial institution, for example, 10 million yuan; the gross profit threshold set by the financial institution, for example, 2 million yuan.

[0091] Circuit Logic:

[0092] First, calculate the total turnover of the enterprise by adding up the amounts of all sales invoices;

[0093] Verify whether the total turnover is greater than the threshold set by the financial institution;

[0094] Calculate the total gross profit, which is the total amount of sales invoices minus the total amount of purchase invoices;

[0095] Verify whether the total gross profit is greater than the set threshold.

[0096] Output Proof:

[0097] The Groth16 protocol generates a zero - knowledge proof that can be verified by the financial institution but does not contain specific invoice data.

[0098] (4) Generate Zero - Knowledge Proof

[0099] The enterprise, through the invoicing platform, calls its invoice data as private input and uses the Groth16 protocol to generate a zero - knowledge proof. The Groth16 proof contains private input and public input. The enterprise only needs to submit the generated proof and the public input (i.e., the thresholds of turnover and gross profit) to the financial institution without disclosing specific invoice data.

[0100] (5) Financial Institution Verifies the Proof

[0101] The financial institution, as the verifier, receives the zero - knowledge proof π and the public input submitted by the enterprise and uses the Groth16 verification algorithm to verify the validity of the proof. The verification process ensures that the total turnover and gross profit of the enterprise meet the requirements of the financial institution, but the financial institution cannot obtain any specific invoice data during the verification process.

[0102] A method and system for generating and verifying electronic invoice credit vouchers based on zero - knowledge proof provided by the present invention ensure that the financial institution can trust the financial proof provided by the enterprise without disclosing the specific invoice information of the enterprise. All invoice data are encrypted and stored on the blockchain to ensure the integrity and security of the data; through the Groth16 protocol, the financial institution can quickly verify the proof of the enterprise, reducing the complexity of data processing and auditing, and at the same time ensuring the credibility of the information submitted by the enterprise.

[0103] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memory, CD-ROM, optical memory, etc.) that contain computer-usable program code.

[0104] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be realized by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate means for realizing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0105] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured article including instruction means, and the instruction means realizes the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0106] These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process. Thus, the instructions executed on the computer or other programmable device provide steps for realizing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that modifications or equivalent replacements can still be made to the specific embodiments of the present invention. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of the claims of the present invention.

Claims

1. A method for generating an electronic invoice credit voucher based on zero-knowledge proof, characterized in that: include: The blockchain-based invoicing platform receives proof requests from enterprises; According to the certification request, obtaining the encrypted electronic invoice information of the enterprise; Generate the total turnover and total gross profit of the enterprise based on the input and output items in the electronic invoice information; Generating a zero-knowledge proof of the enterprise based on the private input in the electronic invoice information and the public input set by the financial institution; The zero-knowledge proof of the enterprise is submitted to the financial institution as an electronic invoice credit certificate.

2. The method according to claim 1, characterized in that Generating a zero-knowledge proof of the enterprise based on the private input in the electronic invoice information and the public input set by the financial institution, including: According to the input invoice amount and the output invoice amount in the electronic invoice information, a zero-knowledge proof of the enterprise is generated through the Groth16 protocol.

3. The method according to claim 1, characterized in that The total turnover and total gross profit of the enterprise are generated based on the input and output items in the electronic invoice information, including: Add the sales invoice amounts in the electronic invoice information to obtain the total turnover of the enterprise; The total gross profit of the enterprise is obtained by subtracting the total amount of input invoices from the total turnover in the electronic invoice information.

4. A method for verifying electronic invoice credit vouchers based on zero-knowledge proof, characterized in that: include: Financial institutions receive electronic invoice credit certificates submitted by enterprises; Verify the validity of the zero-knowledge proof in the electronic invoice credit voucher, and whether the total turnover and total gross profit in the electronic invoice credit voucher meet the requirements of the financial institution; When the zero-knowledge proof is verified to be valid, and the total turnover and total gross profit in the electronic invoice credit certificate meet the requirements of the financial institution, the electronic invoice credit certificate of the enterprise is verified to be successful.

5. The method according to claim 4, characterized in that Verifying the validity of the zero-knowledge proof in the electronic invoice credit voucher includes: Through the verification algorithm of Groth16, it is determined that the zero-knowledge proof in the electronic invoice credit certificate is within the validity period, and then the zero-knowledge proof is valid.

6. The method according to claim 4, characterized in that Verify that the total turnover and total gross profit in the electronic invoice credit voucher meet the requirements of the financial institution, including: If the total turnover is greater than the first threshold set by the financial institution, and the total gross profit is greater than the second threshold set by the financial institution, then the total turnover and total gross profit in the electronic invoice credit voucher meet the requirements of the financial institution.

7. An electronic invoice credit certificate generation system based on zero-knowledge proof, characterized in that: include: The proof request receiving module is used in the blockchain-based invoicing platform to receive proof requests sent by enterprises; An invoice information acquisition module, used to acquire the encrypted electronic invoice information of the enterprise according to the certification request; A proof generation module, used to generate the total turnover and total gross profit of the enterprise based on the input and output items in the electronic invoice information; and to generate a zero-knowledge proof of the enterprise based on the private input in the electronic invoice information and the public input set by the financial institution; The credit certificate returning module is used to submit the zero-knowledge proof of the enterprise as an electronic invoice credit certificate to the financial institution.

8. The system according to claim 7, characterized in that Proof generation module, including: The proof generation submodule is used to generate a zero-knowledge proof of the enterprise through the Groth16 protocol based on the input invoice amount and the output invoice amount in the electronic invoice information.

9. An electronic invoice credit certificate verification system based on zero-knowledge proof, characterized in that: include: The credit voucher receiving module is used by financial institutions to receive the electronic invoice credit vouchers submitted by enterprises; A first verification module, used to verify the validity of the zero-knowledge proof in the electronic invoice credit voucher, and whether the total turnover and total gross profit in the electronic invoice credit voucher meet the requirements of the financial institution; The second verification module is used to verify that the electronic invoice credit certificate of the enterprise has passed the verification when the zero-knowledge proof is verified to be valid and the total turnover and total gross profit in the electronic invoice credit certificate meet the requirements of the financial institution.

10. The system according to claim 9, characterized in that The first verification module includes: The zero-knowledge proof verification submodule is used to determine, through the Groth16 verification algorithm, that the zero-knowledge proof in the electronic invoice credit voucher is within the validity period, and the zero-knowledge proof is valid.

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