How is blockchain technology used in the field of bills?

As an underlying Internet protocol, blockchain has not been favored by Internet companies or IT companies, but financial companies are eager to develop its applications. Some people even boldly predicted that "blockchain is the final form of Internet finance." What is the reason behind this phenomenon? We need to judge from the concept and advantages of blockchain itself.

The success of blockchain technology in Bitcoin has proved the feasibility of programmable digital currency. With the expansion of this technology, and the urgent need to solve a series of problems in the financial field such as duplicate accounting, security attacks and trust relationships, blockchain has a wide range of applications in the financial field, and the application of digital bills can become a breakthrough in its application in the financial field.

Overview of blockchain development

1. Current status of blockchain development

From an international perspective, since the birth of Bitcoin, the first application based on blockchain in 2008, this underlying technology based on network protocols has attracted the attention of more and more financial institutions. The International Monetary Fund (IMF) clearly pointed out in its first digital currency report that "it has the potential to change finance." The British government clearly pointed out in its publication "Distributed Ledger Technology: Beyond Blockchain" that it will first be applied to the traditional financial industry, and the Bank of England is already considering issuing digital currency. The European Securities and Markets Authority (ESMA) put forward the view that "blockchain will bring about huge and profound changes to the entire financial industry." Nasdaq uses blockchain to establish Linq, a private equity trading platform. Banks such as Citi, HSBC, and Wells Fargo have joined the R3 blockchain alliance and set up their own research laboratories. Deloitte provides consulting and auditing with the help of the Rubix platform based on blockchain. Dorian S. Nakamoto, the inventor of Bitcoin, was even nominated for the 2016 Nobel Prize in Economics, etc.

From a domestic perspective, some large enterprises have established special blockchain laboratories dedicated to the research of blockchain technology and its promotion in China's finance, notarization and other fields. The national competent authorities established a special blockchain research team as early as 2014, and held a blockchain-based digital currency seminar on January 20 this year, pointing out the importance of issuing digital currency to reducing the issuance of traditional paper currency, reducing illegal activities such as money laundering and tax evasion, and enhancing the control over money supply and currency circulation, better supporting economic and social development, helping to fully realize inclusive finance, improving the payment system, and promoting economic quality, efficiency and upgrading. It also proposed to further clarify the strategic goals of the central bank's issuance of digital currency, including doing a good job in key technology research, studying digital currency scenario applications, and striving to launch the digital currency issued by the central bank as soon as possible. It can be seen that domestic financial executives attach great importance to the application of blockchain technology in the financial field.

2. Blockchain concepts and characteristics

It can be found that: as an underlying Internet protocol, blockchain has not been favored by Internet companies or IT companies, but financial companies are eager to develop its applications. Some people even boldly predicted that "blockchain is the final form of Internet finance." What is the reason behind this phenomenon? This depends on the concept and advantages of blockchain itself.

Blockchain refers to a distributed, sharable, public ledger that is trusted through a consensus mechanism and can be checked by every participant, but no centralized single user can control it, and it can only be revised according to strict rules and public agreements. It establishes a paradigm of decentralized, trustless credit accumulation and collectively maintains a reliable database, forming a distributed shared ledger that is almost impossible to be changed.

From the perspective of data, blockchain can achieve distributed recording (collective maintenance by system participants) and distributed storage (all nodes can or choose to save data); from the perspective of effect, blockchain can generate a set of chronologically recorded, tamper-proof, and trustworthy databases, and this database is not stored on a central server. Therefore, blockchain technology is a technology that maintains the operation of this distributed database through decentralization, trustlessness, and encryption algorithms.

In summary, it has five major characteristics:

The first is decentralization. Due to the use of distributed accounting and storage, there is no centralized hardware or management organization, the rights and obligations of any node are equal, and the data blocks in the system are jointly maintained by the nodes with maintenance functions in the entire system.

The second is openness. The system is open. Except for the private information of the transaction parties being encrypted, the data of the blockchain is open to everyone. Anyone can query the blockchain data and develop related applications through the public interface, so the information of the entire system is highly transparent.

The third is autonomy. The blockchain uses consensus-based norms and protocols (such as a set of open and transparent algorithms) to enable all nodes in the entire system to exchange data freely and securely in a trustless environment, so that trust in "people" is changed to trust in machines, and any human intervention is ineffective.

Fourth, information cannot be tampered with. Once the information is verified and added to the blockchain, it will be stored permanently. Unless more than 51% of the nodes in the system can be controlled at the same time, the modification of the database on a single node will be invalid. Therefore, the data stability and reliability of the blockchain are extremely high.

The fifth is anonymity. Since the exchanges between nodes follow a fixed algorithm, the data interaction does not require trust (the program rules in the blockchain will determine whether the activities are valid), so the counterparty does not need to disclose their identity to gain trust from the other party, which is very helpful for the accumulation of credit.

3. Impact of blockchain on the financial industry

It is not difficult to see from the characteristics of blockchain: First, blockchain can effectively reduce the operating costs of the financial industry and produce profound changes to the layout of the existing centralized financial system; second, blockchain can drive the birth of new business models through innovation and promote the transformation of traditional financial business models; third, blockchain can reduce trust risks and become the most advantageous weapon for the traditional financial industry to fight against Internet finance (with prominent credit risks); fourth, blockchain is a powerful tool for realizing shared finance and lays a technical foundation for the emergence of self-finance; fifth, blockchain technology encourages developmental collaboration and innovation, and programmable models will promote the emergence of more financial ecosystems, and the de-financialization of the regulatory industry will also occur.

Therefore, blockchain first affects the financial infrastructure, then expands to general financial business, and finally changes the entire financial ecological chain. First, financial infrastructure mainly includes core financial infrastructure and subsidiary financial infrastructure. Core finance refers to financial market infrastructure, including payment system, central government deposit system, securities registration system, etc. Subsidiary financial infrastructure is a broad concept, mainly including credit system, legal accounting system, anti-money laundering information, etc. Second, for financial business, it is possible to select a certain financial product as a breakthrough point. Once sustainable benefits are generated based on blockchain, it will have a strong demonstration effect on other financial products. Third, the evolution of the financial ecological chain is the final form of blockchain application in the financial field. The emergence of self-finance and the construction of a new credit system will become the final model.

The feasibility of integrating blockchain and bills

1. Characteristics and significance of bills

(1) Bill business supports the development of the real economy

Bills are a type of credit instrument used in the flow of money or commodities to reflect the occurrence, transfer and repayment of claims and debts. They can be used for payment settlement in trade and short-term financing of enterprises. First, the bill acceptance link can facilitate the payment and settlement of real enterprises and meet the needs of short-term capital payment between enterprises. Second, the transaction methods represented by endorsement transfer and bill discount between enterprises can provide convenient financing channels and low-cost funds for the real economy, especially small and medium-sized enterprises. Third, the volume of bill business is closely related to macroeconomic development. Through the empirical analysis of bill business and GDP from 2001 to date, it is found that there is a significant positive correlation between the bill acceptance balance, acceptance volume, discount volume and real economic indicators.

(2) Bill business helps promote the development of the money market

First, in the secondary market of bill transactions, that is, the rediscount business between financial institutions has accelerated the financing and adjustment of short-term funds, and has become an important asset business of banks and other financial institutions. Second, monetary policy tools represented by the central bank's rediscount and repurchase have made bills play an important role in monetary policy transmission, enhancing the effectiveness of monetary policy implementation, promoting the adjustment of credit institutions, and guiding the expansion of financing for small and medium-sized enterprises.

(3) Bill business helps enrich financial market products

First, due to the multiple attributes of bills, such as payment, funds, credit, and assets, as well as the diversification of bill-holding institutions and cross-field circulation, derivative products based on bills have become an important exploration to connect the money market and the capital market. Second, bill business is conducive to accelerating the progress of interest rate marketization. Since the price of bill transactions is greatly affected by the supply and demand of funds, it is highly sensitive to the market, and a relatively complete market price index and formation mechanism have been formed, which enables financial institutions to expand the floating range of loans and tiered pricing through customer segmentation.

2. Feasibility analysis of the integration of blockchain and bills

(1) Realizing the decentralization of bill value transfer

Bills are valuable certificates, which always require a hidden "third party" role to ensure the safety and reliability of both parties in the transaction. For example, in electronic bill transactions, the two parties actually go through the information exchange and authentication of the ECDS system of the People's Bank of China; in paper bill transactions, the third party trusted by both parties is the authenticity of the bill. However, with the help of blockchain, there is no need for a third party to supervise and verify the information of the value transfer between the two parties, nor is there a need for specific physical objects as a proof of trust between the two parties, thus realizing the "invisible" transfer of value between points. On the other hand, in actual bill transactions, there is often a role of bill intermediaries that uses information gaps to match. After the point-to-point transaction is realized with the help of blockchain, the existing functions of bill intermediaries will be eliminated and repositioned as participants.

(2) Effectively prevent risks in the bill market

In the current bill market, due to the diversity and profit-seeking nature of the participating institutions, risk events occur frequently. Especially with the economic downturn and the chaos in the intermediary world, many banks have suffered major losses this year. Implicit rules such as opacity, non-standardization and high leverage mismatch have induced various risks.

First, from the perspective of moral hazard, the phenomenon of "selling one ticket multiple times" in paper bills and the asynchronous payment endorsement in electronic bills often occurs. However, since blockchain has an unalterable timestamp and the characteristics of full network disclosure, once a transaction is made, there will be no default, whether it is a paper bill or an electronic bill.

Second, from the perspective of operational risk, the electronic bill system is centralized, and once the central server has problems, it will have disastrous consequences for the entire market. The access of corporate online banking will also transfer more risks to the bank's own network security issues, and the entire risk chain will become longer and longer. With the distributed high fault tolerance and asymmetric encryption algorithm in the blockchain, the risk of human operation is almost zero.

Third, from the perspective of credit risk, the data of blockchain can realize the collection and evaluation of the credit of all participants, and can be controlled in real time. Fourth, from the perspective of market risk, a large number of asset mismatches in the intermediary market not only lead to their own losses, but also tie up the interests of banks. With the programmability of blockchain, it is not only possible to effectively control the balance between the asset side and the liability side of participants, but also to make the entire market transaction price more realistic to the demand for funds with the help of the transparent characteristics of data, thereby forming a more realistic price index, which is conducive to controlling market risks.

(3) Changing the existing electronic commercial bill system structure

The existing Electronic Commercial Bill System (ECDS) is a typical centralized model. The central bank takes the lead in developing a centralized registration and data exchange system. Other banks or enterprises access it through direct connection or online banking agent. This means that all bill acceptance, transactions, collection and other links need to use the ECDS system as a data channel. It is not only a centralized data storage platform, but also a third-party authentication and resource interaction platform.

After adopting the decentralized distributed structure of blockchain, the existing system storage and transmission structure has been changed, and a more secure "multi-center" model has been established. The timestamp can fully reflect the process from the creation to the extinction of the bill. It has the characteristic of traceable history, which makes this model have a new continuous "endorsement" mechanism, which truly reflects the transfer process of bill rights.

(4) Improving operational efficiency

The current bill market is more one-to-one in information exchange. Even through the group mode of instant messaging tools, it is easy to cause information asymmetry and poor timeliness.

First, through the information recording and backtracking of blockchain, it is easy to establish information retrieval and reminders based on keywords or other intelligent methods, thereby improving the effectiveness of information. It can also use its openness to transmit information to demanders more quickly and reduce market asymmetry.

Secondly, since blockchain does not require a centralized server, it greatly optimizes the existing system development model. Once system optimization or changes are needed, there is no need to go through multiple links such as requirements-code-testing-production-verification. This is a major advantage for the current bill system that relies on the system to handle business.

Third, blockchain can greatly change the current organizational structure, management system and administrative intervention, making business decisions simpler, direct and effective, and improving the operational efficiency of the entire bill market.

(5) Regulate market order and reduce regulatory costs

Currently, the operating methods in the bill market vary, and supervision can only be carried out through on-site audits. There is also a lack of rapid review and access to the entire process of business models and circulation.

With the use of smart contracts in blockchain, one can take advantage of the programmable characteristics to control the value limitation and circulation direction of bills while they are circulating by editing a program. For example, limiting discounts to real trade backgrounds; setting asset management bills to not bypass credit scale, etc. This will help to form unified market rules, establish a better order, and further enhance the role of bills in serving the real economy.

Second, the tamper-proof timestamp formed by the connection of blockchain data greatly reduces the cost of regulatory review, and the fully transparent data management system provides a reliable traceability path. At the same time, regulatory rules can also be established through programming in the chain to establish a common constraint code, achieving full coverage and hard control of regulatory policies.

Third, for the rediscount of the central bank’s monetary policy, blockchain can also be used to achieve targeted, constrained or intelligent delivery, and its subsequent value flow can be restricted.

Concept of digital bill construction based on blockchain

1. The concept and advantages of digital bills

The so-called digital bill is not a new physical bill, nor is it a simple virtual information flow. It is a new form of bill presentation developed by using blockchain technology, combined with existing bill attributes, regulations and markets. It is completely different from the existing electronic bill in terms of technical architecture. It has the basis of all the functions and advantages of electronic bills, and integrates the advantages of blockchain technology to become a safer, smarter, more convenient and more promising bill form. Therefore, digital bills can also be understood as a new form of electronic bills based on blockchain technology.

The success of blockchain technology in Bitcoin has proved the feasibility of programmable digital currency. With the expansion of this technology, and the urgent need to solve a series of problems in the financial field such as duplicate accounting, security attacks and trust relationships, blockchain has a wide range of applications in the financial field, and the application of digital bills can become a breakthrough in its application in the financial field. In the future, with the further expansion of this technology, blockchain can be applied to any field in society that has the needs of decentralization, notarization and anti-counterfeiting. Blockchain can also subvert the bottom-level protocol of the Internet and apply it to the field of the Internet of Things, promoting the entire society into the era of intelligent Internet and forming a programmable society.

The analogy between digital bills and electronic bills can refer to the analogy between digital currency and electronic currency. Electronic currency is just the virtualization of physical currency on the Internet. It can only complete the role of payment and settlement, and requires a centralized server to record data. It also needs the support of a third party to establish a trust relationship. For example, what is stored in Alipay is electronic currency. It is just physical currency replaced by electronic information flow. Payment is made through Alipay. The final data recorder is the central server behind Alipay. The value exchange generated requires Alipay as a third-party certification. The electronic currency function of payment and the direction of circulation are also uncontrollable. However, digital currency based on blockchain, with its distributed accounting rules, does not require any central agency or third party to authenticate, and can realize point-to-point transfers. It can also control the circulation of currency through programming to achieve a higher level of intelligence. Compared with electronic bills, digital bills have the following core advantages:

(1) The establishment and data storage of the system do not require a central server or a central application. First, the development cost of the central application and access system is saved. Second, the maintenance and optimization cost of the system under the traditional model is reduced, including equipment investment, data backup, emergency management, etc. Third, the risks brought by the centralization of the system are reduced, and there will be no problems of server crashes or hacker control in the centralized model. The distributed database has a strong fault tolerance function, and the operation of all participants will not be affected by the error of one or several nodes, nor will it affect the further storage and transaction updates of the data. Fourth, the cost of repeatedly recording and saving data under the centralized model is reduced. The data ledger recorded in each participant is both a sub-ledger and a general ledger.

(2) The integrity, transparency and verifiability of data through timestamps allow tracking and querying of any value exchange. This information is not only stored on a certain server or on the machine of a certain participant, but also can be shielded through corresponding technologies to protect business secrets (such as the issuer, the accepting bank, etc.).

First, by recording and accumulating any behavioral data of all participants, it is easy to form a credit analysis and evaluation mechanism, which minimizes the possibility of no one knowing about a default, thereby laying the foundation for establishing a good credit environment.

Secondly, convenient information tracking enables the review of historical data, making it easier to clearly display and control the circulation process of bills. Once a legal dispute occurs, it is easy to exercise relevant rights and pursue claims.

Third, it can effectively control the risks in bill transactions and other bill products. For example, for pledged bills used in bill P2P financial management, their status can be known through data review, preventing the risk of repeated pledge or collusion under the existing model.

(3) The form of smart contracts makes bills programmable and controllable throughout their life cycle. First, the control methods of transactions are more diversified. For example, in actual transactions, there will be a bill holding (double buyout) model. The agreed buyback date can be written into the smart contract in the form of code at the beginning of the transaction, and the bill will be automatically redeemed and bought out after maturity. Second, smart contracts are implemented through code, and their hard control means that the transaction of bills no longer requires offline contracts as a guarantee, avoiding breach of contract during execution.

2. Digital ticket scenarios

In the life cycle of a bill, it has gone through three core links: acceptance, circulation and collection. The following is an analysis of the application scenarios of the three links based on the application characteristics of blockchain:

In the acceptance link, different companies occupy different nodes in the entire network system. If company A needs to issue an invoice for company B, then the acceptor is equivalent to a third-party guarantee for the issuing company A. This is similar to the third-party accounting of Bitcoin, except that Bitcoin competes for accounting by computing power, while the acceptance link is completed by establishing a complete set of algorithms (which may include the acceptor's credit to the issuer, the bank designated by the issuer to open an account, service efficiency, etc.) and generating corresponding data blocks.

Its advantages include: First, unlike the existing acceptance system that requires data exchange and information registration with the central ECDS system, a decentralized bill issuance process is realized; second, it eliminates the trouble of enterprises having to go to the bank where they open an account to open a corporate online banking, which is equivalent to reducing the intermediary transmission party of the online banking; third, by recording the timestamp of the data block, it solves the trust problem of all participants in the bill-holding enterprise, and there is no need to prove the ownership of the bill through information exchange in a centralized system; fourth, it solves the information security problem under the existing model. In the existing model, enterprises mainly access the ECDS system through corporate online banking, which is equivalent to transferring the risk to the information security of the corporate online banking. Once the U-Shield is lost or cracked, it will bring the hidden danger of asset loss. Through the implementation of blockchain, each node has its own private key. Once the private key is lost or cracked, the generated information will be disclosed to the entire network, which is not conducive to committing crimes.

In the circulation link, there are a series of business types, including inter-enterprise circulation, discount, rediscount, rediscount, repurchase, etc. These business types and transaction requirements and restrictions, such as the agreed purchase and resale expiration date for repurchase business, can be realized through programming. In the circulation, you can refer to the transaction scenario in Bitcoin, where the seller publishes the public key and the buyer uses his own private key for matching. It only needs to establish appropriate rules for the third party to complete the information recording and generate data blocks.

Its advantages include: first, it eliminates the need for information circulation in a centralized system; second, it enables point-to-point transactions, ensuring the decentralization of value transfer; third, through smart contracts and traceability of circulation, it effectively avoids moral risks, operational risks and credit risks, and achieves fairness of transactions and authenticity of prices.

In the collection process, since the expiration date of the bill has been written into the code when it is accepted, the program control will automatically allow the holder to send a collection application to the accepting bank when it expires. After the collection is completed, the third party only needs to record the information and generate data blocks according to certain rules.

Its advantages are: first, the value exchange is completed directly. If it is directly linked to fund settlement, there will be no problem of overdue collection. Second, through code control, no other operations can be performed during collection, ensuring the consistency between accounts and actuals.

3. Expanded application of digital bills

In the bill exchange, unlike the designated target transactions in the bill circulation link, more transactions are non-designated targets, and the bill exchange establishes market matching rules to perform code-level matching. The seller node programs and publishes the bills it wants to sell according to its own needs and trading rules, and the buyer node programs and publishes its own buying needs. The bill exchange, as a node in the network, can formulate code matching rules. After the codes of the buyer and seller reach a consensus through the matching rules and are confirmed by both parties, they enter the bill circulation link of the designated target transaction.

According to the existing model, the bill exchange publishes and formulates rules to maintain the operation of the central system. In the blockchain model, it can also be set as a special role node to publish recognized parameter control (such as holidays, interest calculation methods) rules, so that any behavior of the entire network node must comply with these rules to achieve the core functions of the exchange.

In addition, for the information, risk, product and other modules in the bill exchange, the data backtracking function in the blockchain can be used to give full play to its distributed database storage function, conduct data mining on the acceptance, transaction, enterprise, bank and customer information of the bill, and establish a rating and evaluation system for the bill. Accumulate experience in risk warning, risk disposal, risk information, etc. through big data mining and evaluation, model construction, etc. to prevent bill risks. For the active combination of domestic bill products, cross-industry, cross-product, and cross-regional design and reconstruction can be achieved through big data mining to better serve economic and financial development. For the transaction clearing function, it can be considered to use digital currency or data currency associated with physical currency to solve it.

In the custody of paper bills, since paper bills account for a large proportion in the market and will continue to exist for a long time in the future, there is bound to be a demand to convert paper bills into digital bills after custody, and then form the same functions as the original digital bills. In this regard, we can refer to the current business scenario of inquiry and reply when handling discount business of paper bills: the discounting bank sends an inquiry to the accepting bank based on the bills provided by the discounting enterprise, and the accepting bank replies with a message "This bill is accepted by our bank, there is no public notice, no loss and stop payment, and the authenticity is self-determined" after confirmation and verification.

Therefore, analogous to this model, in the digital bill system built by blockchain, the custodian, as a network node, publishes a message (including all elements of the bill) to the network node where the entrusting party is located, and declares that the entrusting party owns the bill asset, the face value of the bill is authentic, and it is currently kept by the custodian. At this time, the third-party node selected to record the information is the accepting bank of the bill. After completing the accounting and generating the data block, it adds the bill asset to the name of the network node where the entrusting party is located, realizing the same circulation and use as digital bills.

The advantages of this method are: first, when the initiator of the message is the custodian node, it has indicated that the inspection and custody of the bill has been completed, and it must be responsible for the authenticity of the bill inspection, which solves the authenticity problem of the bill; second, the acceptance bank verification and accounting are added to prevent the custodian node and the entrusting node from jointly committing fraud, that is, the custodian publishes bill asset information that the entrusting party does not own, which solves the existence problem of the bill; third, the acceptance bank verifies and records the bill, which prevents the acceptance bank, the custodian and the entrusting party from jointly committing fraud. Because the acceptance bank has passed the verification and completed the accounting, it is necessary to provide funds to the holder of the digital bill when it expires in the record, which restricts the acceptance bank and solves the validity problem of the bill.

What issues need further research?

1. Problems with blockchain itself

High energy consumption problem: As we all know, there is a dialectical logic of the impossible triangle in the traditional monetary banking system, and there is also a corresponding impossible triangle in the digital currency economics system built in the blockchain (Chang Jian, 2014), that is, it is impossible to achieve the three requirements of decentralization, low energy consumption and high security at the same time . For example, in the actual application of Bitcoin, the result of its development is the rapid improvement and expansion of computer hardware, and the main cost in the "mining" process is also transferred to the hardware cost and the resulting electricity cost. Therefore, how to use blockchain technology to achieve equity cost benefits and maximize its technical effectiveness will become one of the key points that need to be solved in the future.

Data storage space problem: Since the system built using blockchain needs to record every piece of information from the beginning, and each participating node must download, store and update the data block in real time, once the data of each participating node is completely synchronized, on the one hand, the network pressure is relatively large, and on the other hand, the storage space capacity requirements of each participating node may become a key issue restricting its development.

Dealing with stress resistance: Since the system built on blockchain follows the barrel theory, that is, it always takes into account the worst processing speed and network environment among all network nodes, once blockchain technology is extended to a large-scale transaction environment, its overall stress resistance has not been actually verified. Once the transaction volume generated per second exceeds the system's design capacity, or exceeds the capacity of the weakest node, the transaction will automatically enter the queue for queuing, which will bring a bad experience to users. For example, Bitcoin is set to record 7 transactions per second, and the size of the generated data block is about 1M, but with the increase in its participants, the transaction volume has increased, and the possibility of a node's poor interaction ability and insufficient capacity has increased. The entire Bitcoin network has been seriously overloaded, and there are a large number of transactions in the transaction pool waiting to be packaged into data blocks.

2. Problems in the application of digital bills

In the traditional bill system design model, once a standardized development interface is provided, there are no obstacles to system docking and data interaction across technology platforms. However, with the help of digital bills built with blockchain, each node represents a market participant and has its own corresponding system running. In addition, during the construction of the bill exchange, the alliance chain where the digital bill is located needs to interact with the systems under other technology platforms or other alliance chains for data and function calls, etc., which raises the question of how the digital bill system built on blockchain can be docked with systems under other platforms.

Since the construction of digital bills with the help of blockchain is essentially to replace the construction method of existing electronic bills and realize point-to-point value transfer, but under the premise that the whole society does not publicly issue and use digital currency, how to realize the real-time connection between digital bills and physical currency in fund settlement will be an important problem. For example, in Bitcoin exchanges, the final fund settlement is also offline, through existing bank transfers or third-party payment of physical currency. If the digital bills constructed by blockchain still use the offline physical currency fund settlement method, then the advantages that can be generated based on blockchain will be greatly reduced. If digital currency is issued in the alliance chain where it is located, then the programmability of digital currency itself is substitutable for digital bills. Digital bills can be regarded as non-standard digital currencies with elements such as accepting banks, issuers, due dates, and amounts. There is a certain contradiction between the two. From another perspective, it is also worth further studying the way to link online settlement with reserve accounts in the current electronic bill model to realize the way to bind digital bills with physical currency accounts in network nodes.