Blockchain-based supervised financial leasing method based on zero-knowledge proof and homomorphic encryption

Abstract

The present invention relates to the field of privacy security technology, in particular to a blockchain-supervisable financial leasing method based on homomorphic encryption and zero-knowledge proof. The blockchain-supervisable financial leasing method based on zero-knowledge proof and homomorphic encryption comprises: step (1): the supervisor generates a homomorphic encrypted public key and private key, and publicly places the public key on the chain; the lessor and the leasing platform agree on the rent distribution ratio and the leasing platform submits the transaction to be stored on the chain; the leasing platform and the lessee agree on the daily charging standard and the leasing platform submits the transaction to be stored on the chain; step (2): the lessee, the lessor and the leasing platform generate encrypted transaction information and record it on the chain. The present invention records all transactions through the blockchain, so that the data on the chain cannot be tampered with, and the authenticity and validity of the data are guaranteed. The present invention uses homomorphic encryption technology to encrypt all private data, which well protects the transaction data; at the same time, the use of homomorphic encryption technology can ensure that the transaction information can be supervised by the supervisor while ensuring that the private data is not leaked.

Description

Technical Field

[0001] The present invention relates to the field of privacy security technology, and in particular to a blockchain-regulatory financial leasing method based on homomorphic encryption and zero-knowledge proof. Background Art

[0002] Financial leasing is a new form of financial service that combines physical credit with bank credit under the conditions of modern large-scale production. It is a cross-domain and cross-departmental industry that integrates finance, trade and services.

[0003] At present, blockchain will bring great opportunities for change to all walks of life as an infrastructure. However, since blockchain is essentially a traceable decentralized distributed storage, although it makes data more open and transparent, greatly improving the reliability and credibility of the system, it is also accompanied by the risk of data leakage and privacy leakage. With the further development of the big data era, paying attention to data privacy and security has become a global trend. How to solve the data privacy problem in the process of data sharing and utilization is a difficult problem that needs to be solved urgently. At the same time, although the anonymity of blockchain can protect privacy to a certain extent, it also poses a great challenge to supervision.

[0004] Zero-knowledge proof is a cryptographic method that proves that a party knows or possesses a certain information, but can convince the verifier that a certain assertion is correct without providing any useful information to the verifier. At present, with the gradual improvement of the efficiency of zero-knowledge proof technology, zero-knowledge proof technology has been successfully applied in blockchain systems.

[0005] Homomorphic encryption is a method that supports performing calculations on ciphertext. By using homomorphic encryption technology, all transaction data can be hidden on the blockchain, and the regulator who generates the secret key can decrypt the information through the private key to achieve the purpose of supervision. It can not only protect the transaction privacy of all users on the chain from being obtained by other parties, but also ensure that the regulator can check whether the transaction information is legal when necessary. Summary of the invention

[0006] In order to solve the deficiencies of the prior art, the present invention provides a regulated financial leasing solution based on zero-knowledge proof and homomorphic encryption. The technical solution of the present invention enables participants with different identities to participate in financial leasing, while participants with different identities can protect their own privacy and meet the supervision needs of the regulated party.

[0007] The technical means adopted by the present invention to solve the technical problem are: a regulated financial leasing method based on zero-knowledge proof and homomorphic encryption,

[0008] Step (1): The supervisor generates a homomorphically encrypted public key and private key, and publicly places the public key on the chain; the lessor and the leasing platform agree on the rent distribution ratio, and the leasing platform submits the transaction and stores it on the chain; the leasing platform and the lessee agree on the daily charging standard, and the leasing platform submits the transaction and stores it on the chain;

[0009] Step (2): The lessee, lessor and leasing platform generate encrypted transaction information and record it on the chain.

[0010] Furthermore, when the leasing platform is financing, it submits certification data to investors to prove its operating conditions, wherein the submitted certification data is generated using the encrypted transaction information generated in step (2).

[0011] Furthermore, the investor uses zero-knowledge proof to verify the legitimacy of the proof data, thereby confirming whether the company's operating conditions provided by the leasing platform are true and valid and meet the standards.

[0012] Furthermore, the step (2) specifically includes: the lessee encrypts the ID of the leased property using the homomorphic encryption public key generated by the supervisor to generate an encrypted ID of the leased property; the leased property is provided with a telematics processor on which the public key of the lessor is stored for verifying the signature of the lessor;

[0013] The lessee encrypts the deposit in his account and generates a ciphertext deposit and certificate.

[0014] Furthermore, the lessee sends a lease request transaction to the leasing platform, wherein the lease request transaction includes the encrypted ID of the leased item, the lease time, the ciphertext deposit, the certificate and the signature;

[0015] After receiving the rental request transaction, the rental platform identifies the encrypted ID of the rental item and sends the transaction information of the rental item to the lessor off-chain;

[0016] After the lessor receives the message from the rental platform, he signs and authenticates the rental item, and the rental transaction is completed;

[0017] The lessee sends a return request transaction to the leasing platform, where the return request transaction contains the encrypted ID of the leased item, the lessee's signature, and the time the request was initiated;

[0018] After receiving the return request transaction, the rental platform calculates the rent and deducts it from the lessee's deposit;

[0019] The leasing platform submits a clearing transaction to the chain and distributes the rent according to the agreed distribution ratio; the verification node verifies the clearing transaction. If it passes the verification, the leasing platform and the lessor will obtain the agreed proportion of rental income.

[0020] Furthermore, the verification of the clearing transaction by the verification node includes:

[0021] Whether the rent is distributed according to the agreed ratio recorded on the chain; whether the distributed rent amount is the actual amount paid by the lessee; whether the distribution process is correct.

[0022] Furthermore, the investor adopts a sampling verification method to select a portion of continuous ciphertext clearing transactions from the chain, and asks the financing party to prove that the transaction income of this portion is greater than the income threshold N required by the investor.

[0023] Furthermore, the leasing platform chain calculates the plaintext income of the selected transaction according to the requirements of the investor, and encrypts the ciphertext income using the homomorphic encryption public key; the calculated plaintext income is used as private input, and the ciphertext income is used as public input, which are input into the zero-knowledge proof circuit to generate proof data.

[0024] Furthermore, the proof data is used to prove that: the plaintext income calculated off-chain and the income ciphertext calculated on-chain are corresponding; and the income amount is greater than the income threshold N.

[0025] The method provided by the present invention has the following beneficial effects:

[0026] The present invention records all transactions through blockchain, making the data on the chain tamper-proof and ensuring the authenticity and validity of the data.

[0027] The present invention uses homomorphic encryption technology to encrypt all private data, which protects transaction data well. At the same time, the use of homomorphic encryption technology can ensure that private data is not leaked while transaction information can be supervised by the supervisor.

[0028] The present invention adopts zero-knowledge proof technology to ensure that the authenticity of all ciphertexts can be verified while using homomorphic encryption, thereby ensuring the validity of on-chain data.

[0029] The present invention uses homomorphic encryption technology so that on-chain transaction data can be added by time period, and the leasing platform can directly submit a time period transaction amount to the investor when submitting off-chain transaction amounts, which can compress a large amount of information and thus improve efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 (a) is a diagram of the transaction structure for setting homomorphic secret keys;

[0031] Figure 1 (b) is a standard transaction structure diagram for setting the allocation ratio between the lessee and the car owner;

[0032] Figure 1 (c) shows the transaction structure diagram of the lessee and the car owner setting the daily charging standard;

[0033] FIG. 2 (a) is a structural diagram of a car rental request transaction according to the present invention;

[0034] FIG2( b ) is a structural diagram of a car rental transaction according to the present invention;

[0035] FIG2( c ) is a structural diagram of a request for vehicle return transaction according to the present invention;

[0036] FIG2( d ) is a diagram showing the structure of a clearing transaction according to the present invention;

[0037] Figure 3 The flowchart of the key distribution and preset charging standard of the present invention;

[0038] Figure 4 is a leasing flow chart of the present invention;

[0039] Figure 5 The figure is a financing flow chart of the present invention. DETAILED DESCRIPTION

[0040] In order to facilitate the understanding of the present invention, the present invention is described in more detail below in conjunction with the accompanying drawings and specific embodiments. Preferred embodiments of the present invention are provided in the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive. Example

[0041] This embodiment takes vehicle leasing as an example to introduce in detail the blockchain-controllable financial leasing method based on zero-knowledge proof and homomorphic encryption provided by the present invention.

[0042] The meanings of the terms involved in this embodiment are explained as follows:

[0043] Car owner: The lessor, the owner of the vehicle, deposits the vehicle on the rental platform for rent and receives rent after renting it out.

[0044] Renter: the lessee, the party who rents the vehicle.

[0045] Car rental platform: an intermediary participant in car rental services, providing a rental platform for car owners to use to rent out vehicles, and obtaining a platform commission from the rent after the vehicle is rented out. It is also a financier and, when financing is needed, needs to provide proof to investors to ensure that its platform business volume meets the financing standards.

[0046] Investor: A bank or other investment company that provides funds to the financier.

[0047] Regulator: The market regulator, in the present invention, is the party that provides the homomorphic encryption key, that is, the only party that can decrypt and know the plaintext in order to fulfill its market regulatory responsibilities.

[0048] In-vehicle T-box: A telematics processor, mainly used to communicate with the backend system / mobile phone APP to realize the vehicle information display and remote control of the mobile phone APP. In this embodiment, the user's public key is placed in it, and a program is written so that the T-box can verify the owner's signature transaction with the owner's public key to uniquely unlock the vehicle.

[0049] zk-SNARK proof: Zero-knowledge proof, including proof circuit, proof, verifyKey, proofKey, etc. The prover can use zk-SNARK proof to hide the information that he needs to prove but does not want the third party to know. In this scheme, it is used to prove that the ciphertext on the chain is indeed generated by the correct ciphertext and that the ciphertext is greater than a certain value, etc., without reporting the plaintext information.

[0050] The blockchain-based supervised financial leasing method based on zero-knowledge proof and homomorphic encryption in this embodiment has the following specific processes and steps:

[0051] 1. Encryption key establishment

[0052] Process such as Figure 3 As shown, the specific steps include:

[0053] 1. The supervisor generates homomorphically encrypted public and private keys. The private key secretkeyS is kept by itself, and the public key pubkeyS is publicly placed on the chain through transactions. The supervisor sends a transaction to set up a public key transaction. The transaction structure is shown in Table 1 (a). The transaction contains all transaction type flags TransactionType, the public key pk used by the participants for encryption S And the regulator's signature on the transaction, where the transaction type flag is set to 1, indicating that the transaction is a public key transaction.

[0054] 2. The on-chain verification node verifies the transaction signature with the regulator’s public key. If the verification is successful, the public key pk S Write to the chain.

[0055] 3. After the car rental platform and the car owner have negotiated the allocation ratio offline, the car rental platform sends a transaction to set the allocation ratio. The transaction structure is shown in Figure 1 (b). The transaction contains a transaction flag TransactionType, a ciphertext allocation ratio cipherProportion, a signature SignatureA, and a signature Signature. The transaction flag is set to 2, indicating that the transaction is a transaction to set the allocation ratio. The signature Signature is first signed by the car owner using his private key sk A The cipherProportion signature generates SignatureA, and then the car rental platform uses its own private key sk BSignatureA is signed to generate Signature.

[0056] 4. The verification node on the chain verifies the signature SignatureA with the car owner's public key and the car rental platform's public key. If all verifications pass, it means that cipherProportion is the result of negotiation between the car owner and the car rental platform and is not fake. The cipherProportion is written to the chain.

[0057] 5. After the rental platform and the renter have agreed on the daily charging standard, the rental platform sends a transaction to set the daily charging standard. The transaction structure is shown in Figure 1 (c). The transaction contains a transaction flag TransactionType, a ciphertext allocation ratio cipherDaycost, a signature SignatureB and a signature Signature. The transaction flag is set to 3, indicating that the transaction is a transaction to set the daily charging standard. The signature Signature is first signed by the renter using his private key sk B The cipherDaycost is signed to generate SignatureB, and then the car rental platform uses its own private key sk B SignatureB is signed to generate Signature.

[0058] 6. The verification node on the chain verifies the signature SignatureB with the renter's public key and the rental platform's public key. If all verifications pass, it means that the cipherDaycost is the result of a negotiation between the rental platform and the renter and is not fake. The cipherDaycost is written to the chain.

[0059] 2. Car rental transactions

[0060] Process such as Figure 4 As shown, the specific steps include:

[0061] 1. The renter sends a request for a car rental transaction. The transaction structure is shown in Figure 2 (a). The transaction contains a transaction type flag TransactionType, a ciphertext request for rental vehicle ID cipherVehicleID, a requested rental time, a ciphertext deposit cipherDeposit, a zk-SNARK proof proof, and a signature for the transaction. The transaction type flag is set to 4, indicating that the transaction is a request for a car rental transaction. The requested rental time is calculated on a daily basis. The deposit is the requested time * daily charging standard. The proof needs to prove that the calculation of the deposit is correct, that is, the ciphertext deposit is calculated from the plaintext deposit, and the deposit value is less than the account balance. cipherDeposit is the ciphertext form of the deposit. The balance of each account is also encrypted and stored on the chain using the bank's public key, which means that the user has enough balance to pay the deposit.

[0062] 2. Verify the validity of the transaction on the chain, including: verifying whether the transaction signature is legal and whether the proof is passed. If all verifications pass, the transaction is valid and recorded on the chain.

[0063] 3. The car owner sends a message to agree to the car rental transaction. The transaction structure is shown in Figure 2 (b). The transaction contains a transaction type flag TransactionType, the requested rental vehicle ID cipherVehicleID, the signature IDSignature of the agreed rental vehicle ID, and the signature Signature of the transaction. The transaction type flag is set to 5, indicating that the transaction is an agreed car rental transaction.

[0064] 4. Verify the validity of the transaction on the chain, that is, verify whether the transaction signature is legal. If all verifications pass, the transaction is valid and recorded on the chain. At the same time, T-box can verify that the ID Signature in the transaction is the signature of the car owner. If the verification passes, the vehicle can be started. This ensures that the car rental platform cannot rent out the vehicle without the owner's permission for personal gain.

[0065] 5. After using the car, the renter sends a request to return the car. The transaction structure is shown in Figure 2 (c). The transaction contains a transaction type flag TransactionType, the requested rental vehicle ID cipherVehicleID and the signature of the transaction. The transaction type flag is set to 6, indicating that the transaction is a request to return the car.

[0066] 6. The on-chain verification node verifies the validity of the transaction. If the verification is successful, the number of days usingday between the transaction and the agreed car use transaction is calculated. The total consumption amount cipherDaycost*usingday is calculated using the additive homomorphic property, and the remaining amount is calculated using cipherDeposit-Daycost*usingday and returned to the account balance to update the account balance.

[0067] 7. At this time, the car rental platform receives the transaction that the renter has returned the car, and needs to send a clearing transaction to distribute the total consumption amount according to the agreed distribution ratio. The transaction structure is shown in Figure 2 (d). The transaction contains a transaction type flag TransactionType and is set to 7, requesting the rental vehicle ID cipherVehicleID, and the car rental platform public key pk A , the owner's public key pk B And zk-SNARK proof.

[0068] 8. The on-chain verification node verifies the transaction. If Verifyproof passes, the following can be proved

[0069] ① It is distributed according to the agreed distribution ratio recorded on the chain.

[0070] ② The amount allocated is the actual amount spent by the user, not the amount randomly entered by the car rental platform;

[0071] ③ The allocation process is correct: Since the allocation process is calculated by the car rental platform, it is a plain text calculation, but the allocation result is encrypted on the chain, so it is necessary to prove that the calculation process is correct and not falsified.

[0072] 3. Financing

[0073] Process such as Figure 5 As shown, the specific steps include:

[0074] 1. When the car rental platform needs financing, it applies to the investor as the financing party. The investor selects a part of continuous transactions from the chain, such as one month's transactions, and asks the financing party to prove that his income in this month is greater than 1 million.

[0075] 2. The financier calculates the plaintext income for the month based on the month selected by the investor and the transaction records, and submits a zk-SNARK proof to the investor off-chain.

[0076] Investors only need to verify the proof. If the verification is successful, the following can be proved:

[0077] ① In the selected month, the financing party’s income is greater than 1 million.

[0078] ② The transaction data used by the financing party for calculation corresponds to the on-chain data, that is, the transaction data has not been tampered with.

[0079] 3. Investors can select different months multiple times, or directly select a long period of time for verification to verify that the operating conditions of the financing company meet the financing needs.

[0080] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A blockchain-supervisable financing leasing method based on zero-knowledge proof and homomorphic encryption, characterized in that: include: Step (1): The supervisor generates a homomorphically encrypted public key and private key, and publicly places the public key on the chain; the lessor and the leasing platform agree on the rent distribution ratio, and the leasing platform submits a transaction to set the distribution ratio and stores it on the chain; the leasing platform and the lessee agree on the daily charging standard, and the leasing platform submits a transaction to set the daily charging standard and stores it on the chain; Step (2): The lessee, the lessor and the leasing platform generate encrypted transaction information and record it on the chain. Specifically, the lessee uses the homomorphic encryption public key generated by the supervisor to encrypt the ID of the leased item and generate an encrypted ID of the leased item. The leased item is equipped with a telematics processor, which stores the lessor's public key for verifying the lessor's signature to uniquely unlock the leased item. The lessee encrypts the lessee's account deposit to generate a ciphertext deposit and a zk-SNARK proof proof. The proof needs to prove that the calculation of the deposit is correct, that is, the ciphertext deposit is calculated from the plaintext deposit, and the deposit value is less than the account balance. After the leasing platform and the lessor have negotiated the rent distribution ratio offline, the leasing platform sends a set distribution ratio transaction. The set distribution ratio transaction includes a transaction flag TransactionType, a ciphertext distribution ratio cipherProportion, a signature SignatureA and a signature first Signature. First, the lessor uses his private key sk A The cipherProportion is signed to generate SignatureA, and then the leasing platform uses its own private key to sign SignatureA to generate the first Signature; after the leasing platform and the lessee have negotiated the daily charging standard, the leasing platform sends a transaction to set the daily charging standard. The transaction to set the daily charging standard includes a transaction flag TransactionType, the ciphertext daily charging standard cipherDaycost, a signature SignatureB and a signature second Signature; first, the lessee uses his private key sk B The cipherDaycost is signed to generate SignatureB, and then the leasing platform uses its own private key to sign SignatureB to generate the second Signature; After the lessee has finished using the property, he / she sends a return request transaction to the rental platform. The return request transaction contains the encrypted ID of the rented property. After receiving the return request transaction, the verification node on the chain calculates the rent amount. The rental platform submits a clearing transaction to the chain to distribute the rent according to the agreed distribution ratio. When the leasing platform raises funds, the financing party applies to the investor and submits proof data to the investor to prove its operating conditions. The investor adopts a sampling verification method to select a part of the continuous ciphertext clearing transactions from the chain and asks the financing party to prove that the transaction income of this part is greater than the income threshold N required by the investor; The leasing platform calculates the plaintext income of the selected transaction according to the investor's requirements and encrypts it with the public key of homomorphic encryption to obtain the ciphertext income. The calculated plaintext income is used as private input, and the ciphertext income is used as public input, which are input into the zero-knowledge proof circuit to generate proof data. The proof data is used to prove that the plaintext income calculated by the off-chain addition and the ciphertext income calculated on the chain correspond to each other and that the amount of plaintext income is greater than the income threshold N required by the investor.

2. The blockchain-supervisable financing leasing method based on zero-knowledge proof and homomorphic encryption according to claim 1 is characterized in that: The lessee sends a lease request transaction to the leasing platform, where the lease request transaction includes the encrypted ID of the leased item, the lease time, the ciphertext deposit, the zk-SNARK proof, and the signature of the lease request transaction; After receiving the rental request transaction, the rental platform identifies the encrypted ID of the rental item and sends the transaction information of the rental item to the lessor off-chain; After receiving the message from the leasing platform, the lessor sends a message agreeing to the leasing transaction, and the leasing transaction is completed; The lessee sends a return request transaction to the leasing platform, where the return request transaction contains the encrypted ID of the leased item and the lessee's signature on the return request transaction; After receiving the return request transaction, the on-chain verification node calculates the rent amount and deducts the corresponding amount from the lessee's deposit; The leasing platform submits a clearing transaction to the chain and distributes the rent according to the agreed distribution ratio; the on-chain verification node verifies the clearing transaction. If it passes the verification, the leasing platform and the lessor will obtain the agreed proportion of rental income.

3. The blockchain-supervisable financing leasing method based on zero-knowledge proof and homomorphic encryption according to claim 2 is characterized in that: The verification of clearing transactions by the on-chain verification nodes includes: Whether the rent is distributed according to the agreed rent distribution ratio recorded on the chain; whether the distributed rent amount is the actual amount paid by the lessee; whether the distribution process is correct.

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