Security industry cross-border data sharing method and system based on block chain and DID

Abstract

The invention relates to the technical field of block chains, DID, data cross-border and data sharing, in particular to a security industry cross-border data sharing method and system based on a block chain and DID, and the method comprises the steps: S1, identity registration and authority distribution; s2, data release and contract release; s3, data receiving and contract execution; and S4, supervision auditing: each supervision party issues a supervision intelligent contract through a specified DID identity and a block chain account according to own business characteristics, and each participant participating in data sharing can select the supervision party needing submission, and triggers the corresponding intelligent contract to carry out flow data submission. The method has the advantages that the authenticity of the data in the data sharing process is ensured; digitalization, automation and standardization of a data sharing process are realized; constructing an on-chain identity system; the access and data uploading of the cross-border main body mechanism are facilitated, and the cross-border interaction of the data is facilitated; information errors are avoided, and execution efficiency and transparency of data sharing are improved.

Description

Technical Field

[0001] The present invention relates to the technical fields of blockchain, DID, cross-border data and data sharing, and specifically to a cross-border data sharing method and system in the securities industry based on blockchain and DID. Background Art

[0002] In the securities market, over-the-counter derivatives transactions are usually non-standardized contracts, so it is difficult to use centralized matching transactions. In the implementation process, it is mainly carried out through one-on-one inquiry confirmation between securities companies and each counterparty. If the counterparty is from different countries or regions, the data sharing and transaction confirmation between the counterparty and the securities company must be governed by the regulatory authorities of multiple countries or regions, and the effectiveness, accuracy and completeness of regulatory control are low; at the same time, there are many manual links in the interaction process, which faces greater operational risks.

[0003] To solve the above problems, it is urgent to design a cross-border data sharing system and method for the securities industry based on blockchain and DID to solve problems such as data rights confirmation and user behavior management. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a cross-border data sharing method and system for the securities industry based on blockchain and DID, so as to effectively build a credit evaluation system for trading entities based on DID, and effectively share data and reduce performance costs based on blockchain and smart contracts, while achieving flexible adaptation to the diversified regulatory requirements of cross-regional regulatory agencies.

[0005] In order to achieve the above purpose, a cross-border data sharing method for the securities industry based on blockchain and DID is designed, which includes S1. Identity registration and authority allocation: S11. The data sharing party and the data receiving party register their identities through the decentralized identity module, so that the newly added DID is bound to the blockchain account held and written into its DID document; the DID is authorized according to business needs, and the newly added DID is synchronously forwarded to the supervision and audit module for approval; for the existing DID, identity and authority verification is performed; S12. The data sharing party publishes the DID used in the business scenario. After the data receiving party verifies the authenticity of its DID identity, it subscribes to the blockchain account bound to the sharing party to receive data. Various data regulators publish regulatory rules in the system to supervise and audit business data in the DID dimension; S2. Data publishing and contract publishing: S21. The data sharing party constructs and verifies the business data through the data processing module according to the business rules, and encrypts the data. After completion, the data to be shared is transferred to the cloud disk storage module to obtain the file element data, and the file element data includes the unique identification ID corresponding to the file and the unique feature value of the file; S22. The data sharing party uses the chain interaction module to use its bound blockchain account to transmit the file element data obtained in step S21 to the blockchain system. If there is a business demand, the data sharing party edits the smart contract and publishes it to the blockchain system through the chain interaction module; S3. Data reception and contract execution: S31. After blockchain synchronization, the data receiving party detects the addition of data in the subscribed sharing party blockchain account, obtains the file element data uploaded by the data sharing party from any blockchain node through the chain interaction module, and obtains the FileID, and then obtains the original file through the cloud disk storage module, calculates the file feature value and compares it with the unique feature value of the file obtained on the chain to confirm that the file has not been tampered with; S32. After the data receiving party obtains the data file, it uses the data processing module to decrypt and verify the data. If there is a business demand, the data receiving party confirms the execution of the smart contract issued by the sharing party, and publishes the execution result in the blockchain system for both parties to query; S4. Supervision and audit: Each supervisor publishes a supervision smart contract through its designated DID identity and blockchain account according to its own business characteristics. Each participant in data sharing can select the supervisor to which it needs to report, and trigger the corresponding smart contract to report the process data.

[0006] Preferably, the cross-border data sharing method for the securities industry based on blockchain and DID provided by the present invention also includes other technical features, and the data sharing party and the data receiving party are both domestic or foreign users.

[0007] Preferably, the cross-border data sharing method for the securities industry based on blockchain and DID provided by the present invention also includes other technical features, and the regulatory rules issued by the regulator perform data transparency supervision based on the DID dimension.

[0008] The present invention also designs a system that adopts the above-mentioned cross-border data sharing method in the securities industry based on blockchain and DID, including a data processing module for encapsulating and processing business data, as well as data encryption and decryption operations; a chain interaction module for processing the interaction between the business module and the blockchain system; a DID module for generating a trusted distributed digital identity circulating in the system; a regulatory audit module for performing multi-dimensional supervision and auditing of data generated in the business process and the entire life cycle of the data. The regulatory audit module customizes and sets regulatory and auditing rules in the form of smart contracts to meet the regulatory requirements of cross-border multi-jurisdictional institutions.

[0009] Preferably, the system of the cross-border data sharing method in the securities industry based on blockchain and DID provided by the present invention also includes other technical features. The data processing module specifically includes: a data construction unit, which constructs local data into a specified data format according to the business type; a data verification unit, which verifies the data format and validity; a data encryption unit, which supports multiple data encryption algorithms to realize data encryption processing; a data decryption unit, which supports multiple data decryption methods to realize data decryption processing; the data processing module is connected to the chain interaction module to interact with the blockchain, and is connected to the cloud disk storage module to interact with the cloud disk storage.

[0010] Preferably, the system of the cross-border data sharing method in the securities industry based on blockchain and DID provided by the present invention also includes other technical features, and the chain interaction module specifically includes: a data subscription unit, which supports the acquisition of specified blockchain account information; a contract management unit, which supports the management of smart contracts, the editing of unpublished smart contracts, the query of published smart contracts, contract status and execution results; a contract execution unit, which realizes the release, deployment and execution of smart contracts by interacting with the blockchain system; a permission management unit, which performs permission management on operations in the blockchain in combination with the user's DID identity; the chain interaction module interacts with the data processing module, the DID module and the regulatory audit module, and the chain interaction module includes blockchain data query, acquisition and analysis, generation, deployment, execution and result query of smart contracts, and management of on-chain data permissions.

[0011] Preferably, the system of the cross-border data sharing method of the securities industry based on blockchain and DID provided by the present invention also includes other technical features, and the DID module specifically includes: an identity creation unit, which generates an identity file DID document according to the user core data, and generates a corresponding verifiable certificate VC according to the DID according to the business needs; an identity publishing unit, which supports uploading the identity file and VC to the blockchain and publishing a valid DID digital identity to the system; an identity verification unit, which supports the verification of the validity and authenticity of the DID and VC used in the system; an identity management unit, which supports the life cycle management of the DID in the system, the maintenance of the DID validity period, the cancellation of abnormal or expired DIDs, the change of the corresponding information of the DID document, and the joint regulation of the credit status of the specified DID and writing it into its corresponding DID document; the DID module interacts with the blockchain to realize the blockchain storage and verification of the user core data and prevent data tampering; the DID module interacts with the chain interaction module and the supervision and audit module to realize the data authority management in the system based on the DID, the DID module realizes data query and use management according to the VC verifiable certificate, and the DID generated by the DID module is used as the basis for other modules to manage data and operation permissions.

[0012] Preferably, the system of the cross-border data sharing method in the securities industry based on blockchain and DID provided by the present invention also includes other technical features. The regulatory audit module specifically includes: a business statistics unit, which supports different regulatory agencies to configure customized contracts in various business scenarios; a process review unit, which supports dividing the business process into multiple key nodes and monitoring each process node; a member management unit, which performs audit management on members connected to the system and manages and tracks member behaviors; a system monitoring unit, which supports monitoring of system operation indicators, etc.

[0013] Compared with the prior art, the present invention has the following advantages: 1. Apply the characteristics of blockchain that cannot be tampered with to ensure the authenticity of data during data sharing. By uploading data such as the unique characteristic value of the data file to the blockchain, all participants in the data sharing process can verify the authenticity of the data. At the same time, by leaving traces of the steps of the data sharing process on the blockchain, it is convenient for subsequent supervision and audit verification.

[0014] 2. Based on the characteristics of automatic triggering of smart contracts and the inability to tamper with the results, the data sharing process is digitized, automated and standardized. By writing business rules into smart contracts, the deployment and execution of smart contracts can be automatically processed after the transaction parties verify the DID identity, and the processing process is not affected by external factors, effectively reducing the performance risk in the data sharing process.

[0015] 3. Combine distributed digital identity technology with blockchain for data governance and build an on-chain identity system. In the process of data sharing, the usage behavior data of the sharer and the recipient are fully recorded in the blockchain distributed ledger. A credit evaluation system and trusted standardized measurement can be built around the usage behavior. In this way, the behavior sedimentation and behavior risk management and monitoring of the participants can be achieved. Compared with traditional methods, data sharing behavior risks can be monitored and warned more accurately in real time.

[0016] 4. Based on the characteristics of distributed deployment and multi-party consensus of blockchain, it is convenient for cross-border entities to access and upload data, and facilitate cross-border data interaction. At the same time, multiple domestic and foreign regulatory agencies can be included in the blockchain. Cross-border sharing of data can only be carried out after being jointly reviewed and approved by multiple regulatory agencies, avoiding information errors caused by multiple regulatory processes, reducing the difficulty of multi-party supervision, and improving the execution efficiency and transparency of data sharing. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 , is a schematic diagram of the cross-chain data sharing system module; Figure 2 , is a diagram illustrating the steps of cross-border data sharing method. DETAILED DESCRIPTION

[0018] In order to make the purpose, principle and structure of the present invention more clear, it is further described below in conjunction with the drawings and specific embodiments.

[0019] See also Figure 2 The present invention provides a cross-border data sharing system for the securities industry based on blockchain and DID, which is characterized by including: 1. Data processing module, used to encapsulate and process business data, as well as data encryption and decryption operations. Connect with the chain interaction module to interact with the blockchain to achieve functions including building data to be uploaded, acquiring existing data on the chain, and comparing and verifying data; connect with the cloud disk storage module to interact with cloud disk storage. Specifically, the data processing module consists of a data construction unit, a data verification unit, a data encryption unit, and a data decryption unit.

[0020] The data construction unit constructs local data into a specified data format according to the business type.

[0021] The data encryption unit encrypts system data and supports multiple data encryption algorithms, including national encryption algorithms and international mainstream encryption and decryption algorithms.

[0022] The data decryption unit decrypts system data and supports multiple data decryption methods, including national secret algorithms and international mainstream encryption and decryption algorithms.

[0023] Data verification unit, data verification includes verifying the data format, data validity and other characteristics before submitting the data to the blockchain or cloud disk storage, and verifying the data format, data validity, data consistency and other characteristics of the data obtained from the blockchain or cloud disk storage.

[0024] 2. Chain interaction module, used to process the interaction between the business module and the blockchain system, including blockchain data query, acquisition and analysis, smart contract generation, deployment, execution and result query, and on-chain data authority management. This module interacts with the data processing module to upload formatted business data to the blockchain, and generates corresponding smart contracts according to business instructions; interacts with the DID module to confirm the data rights on the chain, and manages the ownership, viewing and use of data according to the DID provided by the current user; interacts with the supervision and audit module to count business data and realize supervision and auditing in different dimensions. Specifically, the chain interaction module consists of a data subscription unit, a permission management unit, a contract execution unit and a contract management unit.

[0025] The data subscription unit subscribes to blockchain data based on the blockchain account dimension and obtains transaction information, account status information, and consensus information under the specified blockchain account.

[0026] The contract management unit manages smart contracts based on smart contracts. It can edit unpublished smart contracts, query published smart contracts, and query contract status and execution results.

[0027] The contract execution unit interacts with the blockchain system to realize the release, deployment and execution of smart contracts. Before the contract is executed, the VC certificate signed by the user's DID must be checked.

[0028] The permission management unit, combined with the user's DID identity, can manage permissions for operations such as data ownership, query, and use in the blockchain.

[0029] 3. DID module, used to generate trusted distributed digital identities circulating in the system. The generated DID is the basis for other modules to manage data and operation permissions. This module interacts with the blockchain to store and verify the user's core data on the blockchain to prevent data tampering; this module interacts with the chain interaction module and the regulatory audit module to implement data permission management within the system based on DID, relying on verifiable credentials (VC, Verified Credential) to achieve data query and usage management. Specifically, the DID module consists of an identity creation unit, an identity verification unit, an identity issuance unit, and an identity management unit.

[0030] The identity creation unit is used to generate the DID digital identity corresponding to the system user, generate an identity document (DID document) based on the user's core data, and generate the corresponding verifiable certificate VC based on the DID according to business needs to achieve data authorization and permission management.

[0031] The identity publishing unit is used to upload identity documents and VC to the blockchain to ensure the immutability of the documents and to publish a valid DID digital identity to the system.

[0032] The identity verification unit is used to verify the validity and authenticity of the DID and VC used in the system, ensuring that they are consistent with the records in the blockchain and providing a trusted DID system.

[0033] The identity management unit is used to manage the life cycle of DIDs in the system, maintain the validity period of DIDs, cancel abnormal or expired DIDs, and change the corresponding information of DID documents. At the same time, this unit can jointly regulate the credit status of the specified DID based on user operations, user smart contract performance and execution, and regulatory instructions, and write its corresponding DID document to reflect the user's credit rating.

[0034] 4. Supervision and audit module, which is used to conduct multi-dimensional supervision and audit of data generated in business processes and the entire life cycle of data. Supervision and audit rules can be customized through smart contracts to meet the supervision requirements of cross-border multi-jurisdictional institutions. Specifically, the supervision and audit module consists of a business statistics unit, a process review unit, a member management unit, and a system supervision unit.

[0035] The business statistics unit is the core functional unit of regulatory auditing. It can configure customized contracts for different regulatory agencies in various business scenarios through smart contracts. The contracts acquire and count data according to the authority of different regulatory agencies and generate specified results. The calculation results are only visible when the contract is executed.

[0036] The process review unit’s main function is to provide business process operation audits. The main business processes include data lifecycle management processes, smart contract management processes, distributed identity management processes and other business process management. The business processes are divided into multiple key nodes, and each process node can be monitored to ensure the effective execution of process reviews.

[0037] The member management unit audits and manages the members connected to the overall system. The entry and exit of members in the system must be approved to avoid privacy data leakage and business stagnation caused by malicious users. At the same time, member behavior is managed and tracked to meet review requirements.

[0038] The system monitoring unit is used to monitor system operation indicators, including technical indicators such as CPU utilization, system IO, network bandwidth, and storage usage, and business indicators including the number of contracts, the number of data sharing, and the number of users.

[0039] See also Figure 1 The present invention also relates to a cross-border data sharing method, which mainly includes six key steps: S1 identity registration and authority allocation, S2 data release and contract release, S3 data reception and contract execution, and S4 supervision and audit. The specific steps are as follows: In step S11, the data sharing party (domestic or overseas) and the receiving party (overseas or overseas) register their identities through the DID module. A newly added DID needs to be bound to the blockchain account held by the user and written into its DID document. The DID is authorized according to business needs. The newly added DID needs to be synchronously forwarded to the regulatory audit module for approval; if an existing DID logs in, identity and authority verification is required.

[0040] In step S12, the data sharing party publishes its DID used in this business scenario. After verifying the authenticity of its DID identity, the data receiving party subscribes to the blockchain account bound to the sharing party to receive data. Various data regulators (domestic or foreign) publish their regulatory rules in the system to conduct business data supervision and auditing in the DID dimension.

[0041] In step S21, the data sharing party constructs and verifies the business data through the data processing module according to the business rules, and encrypts the data according to the specified method. After completion, the data to be shared is transferred to the cloud disk storage module, and the file element data such as the unique identification ID (i.e. FileID) and the file unique feature value (SM3) corresponding to the file are obtained.

[0042] In step S22, the data sharing party uses its bound blockchain account through the chain interaction module to transfer the file element data obtained in S21 to the blockchain system. If there is a business demand, the data sharing party edits the smart contract and publishes it to the blockchain system through the chain interaction module.

[0043] Step S31, after blockchain synchronization, the data receiver detects the addition of data in the subscribed sharing party blockchain account, and obtains the file element data uploaded by the data sharing party from any blockchain node (domestic or foreign) through the chain interaction module. After obtaining the FileID, the original file is obtained through the cloud disk storage module, and the file feature value (SM3') is calculated and compared with the unique feature value (SM3) of the file obtained on the chain. If the feature values ​​are consistent, it means that the file has not been tampered with.

[0044] Step S32: After obtaining the data file, the recipient uses the specified method to decrypt the data through the data processing module and performs data verification. If there is a business need, the data recipient confirms to execute the smart contract published by the sharing party, and the execution result will be published in the blockchain system. Both parties can query the smart contract execution result in the blockchain system.

[0045] In step S4, each regulator publishes a regulatory smart contract based on its own business characteristics through its designated DID identity and blockchain account. Each participant in data sharing can select the regulator to which it needs to report and trigger the corresponding smart contract to report process data.

[0046] <Example 1> Cross-border transactions in over-the-counter derivatives markets currently have many manual links in the transaction process and high operational risks. There is a lack of effective domestic and overseas data sharing channels, and it is impossible to effectively share transaction instructions and other data domestically and overseas, making it difficult to conduct penetrating supervision of the entire transaction process.

[0047] The embodiment constructed by the cross-border data sharing system and method for the securities industry based on blockchain provided by the present invention is a cross-border income swap system constructed by a securities company based on a blockchain system. This cross-border income swap system mainly involves data sharing between domestic and foreign counterparties and domestic and foreign regulatory agencies. Before participating in data sharing, the counterparty completes identity authentication and obtains a distributed digital identity after approval by the regulatory agency, writes key identity information into the DID document and stores it in the blockchain, and obtains a unique DID and blockchain account. The domestic data sharing party encrypts the transaction instruction data and converts it into a file format and uploads it to the cloud disk, and transmits the file ID and file SM3 code to the blockchain node, and generates a transaction smart contract and publishes it in the blockchain system. The overseas recipient subscribes to the blockchain account of the domestic sharing party and obtains the latest on-chain data transmitted by the sharing party in real time. After obtaining the data, the data recipient downloads the file from the cloud disk and verifies the authenticity of the file, and obtains the transaction instruction after decryption. If the data recipient agrees with the transaction instruction, the transaction is executed through the smart contract issued by the data sharing party, and the contract execution result can be queried in the blockchain system. The data in the above transaction process can be viewed in real time and traced back historically by domestic and foreign regulators connected to the blockchain system, effectively ensuring compliance with regulations.

[0048] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent substitutions or changes according to the technical solutions and novel concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A cross-border data sharing method for the securities industry based on blockchain and DID, characterized by The method comprises S1. Identity registration and authority allocation: S11. The data sharing party and the data receiving party register their identities through the decentralized identity module, so that the newly added DID is bound to the blockchain account held and written into its DID document; the DID is authorized according to business needs, and the newly added DID is synchronously forwarded to the regulatory audit module for approval; for the existing DID, identity and authority verification is performed; S12. The data sharer publishes the DID used in the business scenario. After the data receiver verifies the authenticity of its DID identity, it subscribes to the blockchain account bound to the sharer to receive the data. Various data regulators publish regulatory rules in the system to supervise and audit business data in the DID dimension. S2. Data release and contract release: S21. The data sharing party constructs and verifies the business data through the data processing module according to the business rules, and encrypts the data. After completion, the data to be shared is transferred to the cloud disk storage module to obtain the file element data, which includes the unique identification ID corresponding to the file and the unique feature value of the file; S22. The data sharing party uses the blockchain account bound to the data sharing party to transfer the file element data obtained in step S21 to the blockchain system through the chain interaction module. If there is a business demand, the data sharing party edits the smart contract and publishes it to the blockchain system through the chain interaction module. S3. Data Receiving and Contract Execution: S31. After blockchain synchronization, when the data receiver detects the addition of new data in the subscribed sharing party's blockchain account, it obtains the file element data uploaded by the data sharing party from any blockchain node through the chain interaction module, and obtains the FileID, and then obtains the original file through the cloud disk storage module, calculates the file feature value and compares it with the unique feature value of the file obtained on the chain to confirm that the file has not been tampered with; S32. After the data recipient obtains the data file, it uses the data processing module to decrypt and verify the data. If there is a business need, the data recipient confirms the execution of the smart contract issued by the sharing party and publishes the execution result in the blockchain system for both parties to query; S4. Regulatory audit: Each regulator publishes a regulatory smart contract through its designated DID identity and blockchain account in accordance with its own business characteristics. Each participant in data sharing can select the regulator to which it needs to report and trigger the corresponding smart contract to report process data.

2. A cross-border data sharing method for the securities industry based on blockchain and DID as claimed in claim 1, characterized in that The data sharing parties and data recipients are both domestic or overseas users.

3. A cross-border data sharing method for the securities industry based on blockchain and DID as claimed in claim 1, characterized in that The regulatory rules issued by the regulator are based on the DID dimension for transparent data supervision.

4. A system using the cross-border data sharing method in the securities industry based on blockchain and DID as claimed in claim 1, characterized in that include Data processing module, used to encapsulate and process business data, as well as perform data encryption and decryption operations; Chain interaction module, used to process the interaction between business modules and blockchain system; DID module, used to generate trusted distributed digital identities circulating in the system; The regulatory audit module is used to conduct multi-dimensional supervision and audit of the data generated in the business process and the entire life cycle of the data. The regulatory audit module customizes the regulatory and audit rules through smart contracts to meet the regulatory requirements of cross-border multi-jurisdictional institutions.

5. The system of the cross-border data sharing method in the securities industry based on blockchain and DID as claimed in claim 4 is characterized in that: The data processing module specifically includes: A data construction unit constructs local data into a specified data format according to the business type; Data verification unit, to verify the data format and validity; Data encryption unit, supporting multiple data encryption algorithms to realize data encryption processing; Data decryption unit, supports multiple data decryption methods and realizes data decryption processing; The data processing module is connected to the chain interaction module to interact with the blockchain, and is connected to the cloud disk storage module to interact with the cloud disk storage.

6. The system of the cross-border data sharing method in the securities industry based on blockchain and DID as claimed in claim 4 is characterized in that: The chain interaction module specifically includes: Data subscription unit, which supports obtaining information of specified blockchain accounts; The contract management unit supports managing smart contracts, editing unpublished smart contracts, and querying published smart contracts, contract status, and execution results; The contract execution unit realizes the release, deployment and execution of smart contracts by interacting with the blockchain system; The permission management unit manages the permissions of operations in the blockchain in combination with the user's DID identity; The chain interaction module interacts with the data processing module, the DID module and the regulatory audit module. The chain interaction module includes blockchain data query, acquisition and parsing, smart contract generation, deployment, execution and result query, and on-chain data authority management.

7. The system of the cross-border data sharing method in the securities industry based on blockchain and DID as claimed in claim 4 is characterized in that: The DID module specifically includes: The identity creation unit generates an identity document DID document based on the user's core data, and generates a corresponding verifiable certificate VC based on the DID according to business needs; Identity publishing unit, which supports uploading identity documents and VC to the blockchain and publishing valid DID digital identities to the system; Identity verification unit, which supports the validity and authenticity of DID and VC used in the verification system; The identity management unit supports lifecycle management of DIDs in the system, maintains the validity period of DIDs, cancels abnormal or expired DIDs, changes the corresponding information of DID documents, and jointly regulates the credit status of specified DIDs and writes them into their corresponding DID documents; The DID module interacts with the blockchain to implement blockchain notarization and verification of user core data and prevent data tampering; the DID module interacts with the chain interaction module and the regulatory audit module to implement DID-based system data authority management. The DID module implements data query and usage management based on VC verifiable credentials. The DID generated by the DID module serves as the basis for other modules to manage data and operation permissions.

8. The system of the cross-border data sharing method in the securities industry based on blockchain and DID as claimed in claim 4 is characterized in that: The regulatory audit module specifically includes: Business statistics unit, which supports different regulatory agencies to configure customized contracts in various business scenarios; The process review unit supports dividing the business process into multiple key nodes and monitoring each process node; Member management unit, which conducts audit management on members connected to the system and manages and tracks members' behaviors; System monitoring unit, supports monitoring of system operation indicators, etc.

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