1 Introduction

As the booming of the global internet, the vast ocean of our universe has become a “global village”, and the modern service industry transactions grow increasingly convenient. Although modern information technology is finding wider and wider application in modern communication and transaction, the essential issues of trusted transaction in modern service industry has not been improved substantially. Modern information technology has raised higher requirements for trusted transactions.

In the past, international and domestic transactions with banks as bookkeeping and transfer intermediaries were based on state and bank credit, requiring both parties or multiple parties to trade on the basis of banks, which have three main requirements for each party:

  1. 1.

    Immutability: the transaction accounts can’t be changed or altered by either party upon the consensus reached by both parties (signature, seal, etc.).

  2. 2.

    Unforgeable: the transaction accounts cannot be forged by anyone or any institution.

  3. 3.

    Undeniable: the transaction record or contract execution cannot be denied or prevented by either party without the alteration in the case of mutual agreement on the transaction or contract.

The “Three Prohibition Principles” are the basis of trusted transactions. And intermediaries such as banks must ensure that multiple disbursements of funds are prevented.

Blockchain is a new technology applied in Satoshi Nakamoto’s paper “Bitcoin: A Peer-to-peer Electronic Cash System” [1], which is becoming the strategic frontier technology that each country competes to develop. As a boom value Internet technology, it is inevitable to combine with modern service industry and internet finance. It technically realizes the “three prohibition principles” (Immutability, Unforgeable, Undeniable) and fundamentally eliminates the “double payment problem” in transactions. In 2015, Ethereum realized smart contracts [2, 3], which pushing blockchain technology on a new level, taking a big step forward for trusted transactions in modern services, and laying a solid foundation for the realization of trusted transactions. Blockchain technology mainly has the following several innovations:

  • Model innovation: Blockchain pioneered a transaction model that reduced intermediation, and open up a new model for tamper-modifiable data, undeniable, and traceable applications.

  • Technological innovation: Blockchain is a new application model combined by distributed data storage, point-to-point transmission, consensus mechanism, encryption algorithm and other computer technologies with a new structure.

  • Application (convergence) innovation: Blockchain technology can be applied in financial transactions, certificate storage, traceability, “Internet of Things”, medical and health care, smart city, anti-security identification, supply chain management, data sharing and transaction, digital identity and other fields. The technical characteristics can be used to play an important role in blockchain + (mainly in blockchain technology) or in + blockchain (using one or several characteristics of blockchain technology).

2 Theoretical and Technological Basis of Trust Transactions

  • Trusted transactions in modern service industry involve internet financial payment, electricity rapid transactions, service smart contract and other modern means. Because of the fund flow and the exchange of goods and services, the process is still necessary to guarantee the transaction and service records unforgeable, immutability, undeniable and traceable in addition to basic safety and efficiency. The emergence of the blockchain, especially the alliance chain, not only realizes the efficient transaction and security guarantee of the modern service industry, but also realizes the “three prohibition principles” of the transaction ledger under the Internet conditions. The main theories and technologies of the blockchain and alliance chain include: modern cryptography theory and technology, consensus algorithm, and distributed complete ledger storage technology. The application of smart contracts on the blockchain provides a reliable basis for the automatic execution of contracts.

2.1 Cryptographic Principle and Technology

  • In 1976, Whitefield Diffie and Martin Hellman put forward the idea of public key cryptography, which marked the birth of modern cryptography and was a milestone event in the history of international cryptography. Modern cryptography theory and its derived related technologies are one of the three major supporting technologies that constitute the blockchain system, and they are the practical theoretical and technical foundation of the blockchain technology. Blockchain technology relies on encryption technology to achieve data security, digital certificates are mainly used to identity authentication, ensuring that the signed data is undeniable or traceable. Under the alliance chain, these two technologies are internally connected and play a crucial role in the “three prohibition principles” of the blockchain ledger [4, 5].

  • At present, ECDSA and EdDSA are the most widely used signature algorithms based on ECC in the world. The national standard of digital signature algorithm based on Chinese elliptic curvilinear is SM2, and that of digital certificate is SM9.

2.2 Consensus Mechanism

  • The consensus mechanism is to formulate a series of rules to act. This rule includes transaction rules and data consistency rules. Trusted transactions in modern services require blockchain systems to solve the compliance and consistency of transaction data. Compliance means that all records entering the ledger must be regular, and irregular transactions cannot be entered or should be marked as invalid. Consistency means that all accounting nodes must keep the same transaction data, only by which transaction data can be ultimately prevented from being tampered with the help of password technology. And the correct transaction data can be effectively and timely restored when part of the node data is illegally tampered with [6]. The main consensus algorithms are:

  • lottery-based consensus: proof of workload mechanism (POW), proof of equity (POS);

  • voting-based consensus: practical Byzantine general algorithm PBFX, Paxos algorithm;

  • fault-tolerance-based consensus: RAFT and KAFKA.

2.3 Distributed Storage Technology

  • Distributed storage is one of the other pillar technologies of blockchain systems which decentralize the storage of data in multiple separate devices [7]. Distributed storage technology in the blockchain has the following effects:

  • Ensure consistency of data;

  • Prevent illegal tampering;

  • Guarantee data availability: Prevent transactions system and data from unavailability after failure of some nodes in the system;

  • Distinguish fault tolerance: Distributed storage transactions system still works when some nodes stop working due to failure.

2.4 Smart Contract

  • The concept of smart contract was introduced by Nick Szabo in 1995. The development of smart contract has gone through three stages of concept, realization concept and rapid development. Although Nick Szabo proposed and described the application scenarios of smart contracts, he failed to find the right way to implement them. Until 2015, the emergence of Ethereum made smart contracts to be convenient and quickly realized [8, 9].

  • Smart contracts often require input data to trigger the execution conditions, which and then output the execution results. The traditional Internet uses different network protocols, which leads that the smart contracts cannot directly read the data on the Internet. To solve the problem of data acquisition, the “prediction machine” is needed, which is a middleware connecting blockchain to the traditional Internet. It can access data from the Internet and actively feeds it back to smart contracts on the blockchain.

3 Trusted Transactions Overall Framework

3.1 Overall Framework

  • The trusted transaction overall framework is designed for enhance the transactions reliability, convenience, accuracy and security in modern service industry. It can greatly enhance the data protection degree and transaction credibility, and its scalable application scenarios can be extended to other industries, such as item traceability, public management, supply chain and other fields. Figure 1 below is the overall framework of trusted transactions.

Fig. 1.
figure 1

Overall framework of trusted transactions

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3.2 Trusted Transaction Foundation Design Based on Blockchain

  • At the storage layer, we design multiple chains to achieve a combination of flexibility and efficiency: Membership Blockchain, Transactions Blockchain, Commodity Blockchain, and Evaluation Blockchains:

  • Member Blockchain (MBC) mainly authorize and manage users by the authority management department. These users participate in transactions through authorized digital certificates and are the subject of trusted transactions.

  • Transaction Blockchain (Transaction Blockchain, TBC) is used to record the transactions of all parties, which involves in the commodity ID or service ID, the transfer amount of transaction funds, the signature of the transaction, and the signature of the endorsement node in some cases.

  • Commodity chain (Commodity Blockchain, CBC) is the description of goods, which mainly includes the main parameters of the commodity. For transaction efficiency and transaction block restrictions, transaction chain only recorded the ID in order to be able to trace and to prevent the transaction of commodity description and parameters from different disputes.

  • Evaluation Blockchain (EBC) mainly records the score and use evaluation by member users. Through the analysis of these data and machine learning methods, services can be provided for the credit and commodity recommendation of merchant members.

On the consensus algorithm selection, our framework is alliance chain, which can choose efficient and safe algorithm as practical Byzantine general (PBFT) consensus algorithm and consistency RAFT algorithm, and do not need to use waste energy workload (POW) algorithm. We can design the algorithm pool, and choose different efficient algorithm according to different needs.

Many services and products need the support of smart contract. Such as Go, java, or everything with a Turing-complete linguistic environment was recommended. Micro-service framework provides flexibility, scalability, scalability, and high availability, so smart contracts will be structured based on microservice organizations. The permission management involving the choice of digital certificates and signature algorithms, and has a crucial impact on the security and performance of the whole system. National standard SM2 and SM9 was used as the standards for digital signatures and digital certificates, and the CdDSA algorithm was transformed to improve security and overall system efficiency.

4 Trusted Transactions Services: Big Data Credit Investigation and Credit Evaluation

The credit economy is the advanced form of social economy. Credit assessment by enterprises or individuals is crucial in modern transactions. How to build on modern service transactions based on blockchain? How to establish a real-time modern service credit investigation and credit evaluation structure that can achieve high service credit investigation accuracy and regulatory performance? We discuss the following issues on the basis of the e-commerce platform:

4.1 Research on Dynamic Credit Information Collection, Management and Maintenance Methods of Trusted Transactions in Modern Service Industry

There are many sources of credit investigation and credit data in modern service industry, including transaction data (TBC) basing on blockchain, user basic information (MBC), and others data (including government, bank and other chain data).

By adopting the service credit investigation data sharing mechanism based on the idea of open data, constructing the license alliance chain, collecting static and dynamic data of credit investigation, and integrating strong, medium and weak data sources, redundant data of credit investigation data collection can be reduced, the operation cost of service credit investigation and the cost of resource contention can be reduced, and the problem of service credit investigation information island can be solved. Isolation verification, cross verification, data desensitization and other technologies can improve the application scope of data, and at the same time ensure the security of credit investigation data and the data privacy [10].

In the data preprocessing stage, the unstructured data needs to be defined effectively, transformed into structured data, and normalized. For structured data, ETL technology is used to extract and put characteristic values with high correlation between credit investigation and credit into the blockchain of credit investigation after numerical transformation to prevent artificial tampering. For the new credit investigation data obtained in the future, it can be added to the subsequent blockchain of credit investigation and indexed according to the account address to prevent the disclosure of sensitive data.

4.2 Research on Establishing Dynamic Service Credit Evaluation Model by Using On-Chain Transaction Data and Online Available Credit Data Through Regression, Bayesian, Decision Tree and Other Machine Learning Methods

The processing framework based on feature selection is adopted to mainly analyze multi-trusted data sources. The choice of model training adopts regression, Bayesian classification algorithm, decision tree and deep learning algorithm based on artificial neural network or the combination of more than two algorithms. Through a large amount of data training and comparison, high accuracy models are deployed in the credit investigation framework and regulatory framework.

Applying the above credit prediction method and the data analyze processing platform, and using techniques such as statistics, machine learning algorithm to evaluate risk, we can increase the analysis of customer needs. Through multi-angle and multi-dimensional segmentation of user groups, we make a comprehensive analysis of users’ integrity as far as possible, and help credit investigation agencies to control risk, cross check, prevent fraud and evaluate credit.

4.3 Research on Applying Enterprise or Individual Credit Information Obtained from Evaluation Model to Modern Service Industry Supervision, and Re-establishing Dynamic Penetrating Supervision Model Based on Blockchain Transaction

High-credit entities can be given a higher credit limit in supervision and increase the amount and cycle of payments in smart contract validation. In the case of credit-crossing entities, transactions will be reduced or banned, and the application of smart contracts will be subject to stricter rules. By adding the supervision mechanism into the consensus algorithm, the credit investigation model and credit evaluation results can be supervised in real time.

4.4 Research on Dynamic Updating the Credit Model Mechanism and the Real-Time Credit Supervision Model

In order to ensure the real-time credit evaluation of the entity (enterprise and individual users), the credit evaluation system will update the users credit rating timely when new entity data and transactions are generated. The framework is designed with high performance to ensure that high-frequency transactions runs smoothly. Meanwhile, higher security and privacy are needed to protect data. We improved the performance by studying the storage methods on and off the chain to reduce the data size on the chain, higher performance can be realized by isolation validation, sharding, layering or a combination of multiple methods.

5 Summary

This paper discussed on trusted transaction framework of blockchain, theoretical and technical support foundation, smart contract technology application, trusted big data credit investigation, credit evaluation model and other models, we conduct research on the improvement of the credibility, convenience, scalability, supervision, accuracy and security of transactions in modern service industry, and lays a solid foundation for the further establishment of modern service industry trusted transactions platform to provide theoretical and technical support.