A blockchain multi-party smart contract method for cryptocurrency payment channel networks

Abstract

The present invention discloses a blockchain multi-party smart contract method for a cryptocurrency payment channel network, which is used to solve the collusion problem existing in the cryptocurrency payment channel network. The method includes system initialization, multi-party smart contract establishment and sequential equilibrium game based on the multi-party smart contract. The present invention includes three steps. First, the system is initialized and a distributed watchtower model is deployed so that users can update their channel status proof after each transaction is completed without ensuring long-term online status. Then, four smart contracts are established for the cryptocurrency payment channel network to defend against possible collusion attacks in various outsourced watchtower scenarios. Finally, the multi-party smart contract is used to ensure that the system's multi-party complex game process can converge to a sequential equilibrium game, and the game tree is used to visualize the equilibrium point of the game. The blockchain multi-party smart contract method disclosed by the present invention can not only solve the problem of collusion attacks in outsourced watchtower scenarios, but also effectively reduce the false alarms of the watchtower and improve regulatory efficiency.

Description

Technical Field

[0001] The present invention relates to a blockchain multi-party smart contract method for a cryptocurrency payment channel network, belonging to the field of Internet and blockchain technology. Background Art

[0002] With the massive expansion of cryptocurrency users and transactions, scalability has become a pressing issue. Low transaction throughput and high transaction fees severely constrain the development of cryptocurrencies. To address these challenges, payment channel networks (PCNs) offer a promising solution for small-value, high-frequency transactions. PCNs allow parties to modify settlement schemes to conduct off-chain transactions. Specifically, the blockchain only records the opening and closing of a channel and provides security for off-chain transactions. Parties only write transactions to the blockchain to create and close the payment channel; however, there is no limit on the number of off-chain transactions. To prevent one party from being offline and the other from being able to close the payment channel and retrieve funds, payment channels allow participants to independently close the channel by sending the latest channel state proof (CSP) at any time. However, the blockchain cannot verify that the submitted state is up to date, and malicious participants could send fraudulent CSPs to close the payment channel and obtain additional rewards. This security risk requires channel participants to regularly monitor transaction status online and synchronize with the blockchain. Consequently, most blockchain users face security issues when implementing off-chain transactions in payment channels.

[0003] Watchtower technology has recently shown great potential to address these issues. Large-scale blockchain communities have begun implementing watchtowers as mechanisms for monitoring off-chain payment channels, thereby mitigating the security risks of channel deposits. The core concept is to monitor counterparty fraud and publish default information, allowing for compensatory transactions to be conducted through a third-party agent. Once a watchtower discovers that a payment channel is being settled through a fraudulent client service provider, security mechanisms are activated to immediately help users recover losses and punish malicious participants. However, watchtowers can compromise the security of payment channels. If the watchtower is a trusted third party, users can freely go offline without worrying about the payment channel being maliciously closed. However, in reality, neither watchtowers nor payment channel participants are necessarily trustworthy, as watchtowers can be passive or collude with malicious nodes in the channel to cause losses to honest users. Some researchers have also studied the watchtower collusion problem, combining game theory with smart contract methods to address collusion attacks in PCNs. However, single-watchtower mechanisms suffer from false positives. It is difficult to accurately determine whether a false positive is related to collusion, which affects the efficiency and quality of transaction monitoring. Currently, there is no widely adopted method that can effectively prevent collusion problems in PCNs while also reducing watchtower false alarms and improving regulatory efficiency. Summary of the Invention

[0004] Purpose of the Invention: To address the problems and shortcomings of existing technologies, this invention proposes a blockchain multi-party smart contract method for cryptocurrency payment channel networks, designed to prevent collusion among participants in these networks. This method not only addresses collusion attacks within cryptocurrency payment channel networks, but also reduces false alarms from watchtowers, improving regulatory efficiency.

[0005] To solve the above problems, the technical solution of the present invention is as follows: a blockchain multi-party smart contract method for a cryptocurrency payment channel network, comprising the following steps:

[0006] Step 1: System Initialization. This system consists of three roles: watchtowers, transactors, and counterparties. Watchtowers are responsible for real-time monitoring of the payment channel network and regularly updating channel status certificates. Transactors are responsible for hiring watchtowers and sending them channel status certificates. Counterparties maximize their own interests by selectively signing smart contracts and sending channel status certificates. This system presents the risk of collusion between counterparties and watchtowers, as well as between watchtowers themselves, to achieve additional benefits.

[0007] Step 2: Establish four smart contracts to defend against possible collusion attacks in various outsourced watchtower scenarios. The specific steps are as follows:

[0008] Sub-step 2.1: Build a watchtower smart contract. The watchtower smart contract is signed by the transaction party and two watchtowers, allowing the transaction party to entrust the watchtower to monitor the payment channel.

[0009] Sub-step 2.2: Construct a collusion smart contract. The collusion contract is signed between two watchtowers and aims to break the equilibrium of the watchtower contract.

[0010] Sub-step 2.3: Construct a fraud smart contract. The fraud contract is signed by the counterparty and a watchtower to prevent a watchtower from colluding with the counterparty to obtain additional benefits by betraying another watchtower.

[0011] Sub-step 2.4: Construct an anti-collusion contract. The transacting parties only sign an anti-collusion contract with the watchtower that first reports the collusion, ensuring that the watchtower that reports the collusion will not be punished by the watchtower contract.

[0012] Step 3: Sequential Equilibrium Game Based on Multi-Party Smart Contracts. The operation of the watchtower and the employer (transaction party and counterparty) in the system is a complex game process. Multi-party smart contracts can ensure that this process can achieve a unique sequential equilibrium.

[0013] Among them, step 1: system initialization, the details are as follows:

[0014] This system involves three roles: watchtowers, transacting parties, and counterparties. Watchtowers are responsible for real-time monitoring of the payment channel network and regularly updating channel status proofs. Transacting parties are responsible for hiring watchtowers and sending them channel status proofs. Counterparties maximize their own interests by selectively signing smart contracts and sending channel status proofs. Participants in off-chain transactions are required to update their channel status proofs after each transaction. Because it is impractical to keep these participants online all the time, participants can rent multiple watchtowers to facilitate off-chain transactions by signing smart contracts. However, collusion is still possible in this scenario. Specifically, counterparties can contract with watchtowers to commit fraud and obtain additional benefits. Alternatively, distributed watchtowers could collude with each other to defraud them of commissions. In this system, watchtowers and counterparties have multiple options during the transaction process: they may complete the transaction honestly or they may collude or betray to maximize their profits.

[0015] Step 2: Establish four smart contracts to defend against possible collusion attacks in various outsourced watchtower scenarios. The details are as follows:

[0016] Sub-step 2.1: Build the Watchtower smart contract.

[0017] The watchtower contract is actually the transaction party ( ) and two outsourced watchtowers and The signed contract allows the trading party to entrust and Monitoring payment channels. However, before monitoring a payment channel, a watchtower must pay a deposit to the watchtower contract. Note that the deposit is refunded after the watchtower's timely response to the latest channel state proof (CSP) is verified and proven correct. Watchtowers that submit fraudulent CSPs lose their deposit. If only one watchtower provides a correct CSP, the deposit of the watchtower that submitted the incorrect CSP is paid to the trustworthy watchtower as a reward (after deducting necessary fees). While it may seem that two watchtowers colluding might maximize their reward, both watchtowers are likely to remain honest because they know that collusion is unstable and the other party may betray and collude to secure their optimal reward. Therefore, they can obtain a high reward by refusing to collude.

[0018] Sub-step 2.2: Construct the collusion smart contract.

[0019] Collusion contracts aim to disrupt the equilibrium of watchtower contracts. Furthermore, they impose additional rules that influence the payoffs of each party, making collusion the most profitable option. In this contract, a watchtower initiating collusion pays a bribe to another watchtower to encourage collusion. Furthermore, both parties pay a deposit upon signing this contract. This deposit is deducted in the event of defection.

[0020] Sub-step 2.3: Construct the fraud smart contract.

[0021] A fraud contract is signed between a transaction counterparty and a watchtower. This contract modifies the reward and penalty mechanism, incentivizing watchtowers to join the conspiracy and send fraudulent CSPs to terminate the transaction channel, thereby further defrauding the transaction counterparty's transaction funds and the other watchtower's deposit in the watchtower contract. The rules of the fraud contract inevitably affect the compensation of each party. Therefore, when signing this contract, the transaction counterparty and the watchtower will pay a deposit, and the deposit of the party that betrays the contract will be deducted.

[0022] Sub-step 2.4: Construct an anti-collusion contract.

[0023] The anti-collusion contract allows a watchtower that reports to a trading party to secretly betray the other party while pretending to follow the collusion. Without this exemption, the watchtower will not voluntarily report the collusion: (1) If the watchtower reports and complies with the collusion contract, it will lose its deposit in the watchtower contract. (2) If the watchtower reports to the trading party and then betrays the collusion, it will lose its deposit in the collusion contract. In any case, reporting seems less profitable than not reporting. Accordingly, the anti-collusion contract guarantees that the watchtower that reports the collusion will not be punished by the watchtower contract. The watchtower can pretend to follow the collusion, which can also avoid the punishment for betraying the collusion contract. On the other hand, if the collusion is discovered through secondary proofreading, the anti-collusion contract will reward the watchtower that reported the collusion. Therefore, the report is not only risk-free but also profitable. In short, the anti-collusion contract breaks the collusion by incentivizing betrayal among watchtowers, which will create distrust among watchtowers and ultimately prevent collusion.

[0024] The relationships between the four smart contracts are as follows: A watchtower contract is a contract of employment between a transaction party and a watchtower. A collusion contract is designed as a conspiracy between two watchtowers to obtain additional rewards. As analyzed in the fraud contract, collusion between a transaction party and a malicious watchtower is possible. An anti-collusion contract is designed to effectively defend against both of these collusion attacks.

[0025] Step 3: Ensure that the system's multi-party complex game processes can converge to sequential equilibrium games through multi-party smart contracts, and use the game tree to visualize the equilibrium points of the game. The details are as follows:

[0026] The operation of the watchtower and the employer (transaction party and counterparty) in the system is a complex game. Transactions in the payment channel are anonymous, and channel participants lack complete information. Based on this, the present invention constructs an extended form of the game with limited incomplete information and further uses a game tree to visualize the equilibrium points of the game, ensuring that the process can achieve a unique sequential equilibrium.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] (1) The blockchain multi-party smart contract method for the cryptocurrency payment channel network proposed in this invention can not only solve the collusion attack problem in the cryptocurrency payment channel network, but also reduce the false alarms of the watchtower and improve the supervision efficiency.

[0029] (2) The present invention uses four smart contracts to constrain the complex game process in the multi-party cryptocurrency payment channel and models it with a game tree model, which can ensure that each contract has a unique sequential equilibrium and that the parties will never collude or betray the contract. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A blockchain multi-party smart contract and its relationship diagram for a cryptocurrency payment channel network.

[0031] Figure 2 This is a framework diagram of the multi-party smart contract system.

[0032] Figure 3 This is the first game tree dominated by the watchtower contract.

[0033] Figure 4 This is the second game tree dominated by the watchtower contract and the collusion contract.

[0034] Figure 5 This is the third game tree dominated by the watchtower contract and the fraud contract.

[0035] Figure 6 This is the fourth game tree dominated by watchtower contracts, fraud contracts, and collusion contracts.

[0036] Figure 7 This is the fifth game tree dominated by the watchtower contract, the fraud contract, and the anti-collusion contract.

[0037] Figure 8 This is the sixth game tree dominated by all contracts. DETAILED DESCRIPTION

[0038] In order to deepen the knowledge and understanding of the present invention, the present invention is further illustrated below with reference to specific embodiments.

[0039] Example 1: See Figures 1-8 , a blockchain multi-party smart contract method for a cryptocurrency payment channel network, comprising the following steps:

[0040] Step 1: System initialization, as follows:

[0041] First, the blockchain system roles for a cryptocurrency payment channel network are initialized. These roles primarily include three: watchtowers, transactors, and counterparties. Watchtowers are responsible for real-time monitoring of the payment channel network and regularly updating channel status certificates. Transactors are responsible for hiring watchtowers and sending them channel status certificates. Counterparties maximize their interests by selectively signing smart contracts and sending them channel status certificates. Next, rules for renting watchtowers are established. Participants in off-chain transactions need to update their channel status certificates after each transaction, but keeping them online for extended periods is unrealistic. Therefore, smart contracts are implemented to enable watchtowers to facilitate off-chain transactions. Finally, the main scenarios for collusion within the system are identified. Using these rules, counterparties can contract with watchtowers to commit fraud and obtain additional profits. Outsourced watchtowers may also collude with each other to defraud larger commissions.

[0042] Step 2: Establish four smart contracts to defend against possible collusion attacks in various outsourced watchtower scenarios. This step consists of four sub-steps. The contract parameters involved in these step descriptions are described as follows:

[0043] • : The deposit paid by the counterparty and the watchtower to the watchtower contract.

[0044] • : The cost paid by a watchtower to monitor a payment channel.

[0045] • :Watchtower 1( ) in a conspiracy contract to the Watchtower ( ) Bribes paid.

[0046] • : The deposit paid by the watchtower in the collusion contract.

[0047] • :Transaction Party( ) agree to compensate Watchtower for its costs of monitoring payment channels.

[0048] • : The cost of secondary verification when the latest CSP feedback from two watchtowers is inconsistent.

[0049] • : The counterparty can obtain additional compensation by publishing fraudulent customer service providers.

[0050] • : Deposits paid by counterparties and watchtowers in fraudulent contracts.

[0051] • : The bribe that the other party agrees to pay to the detention center in a fraudulent contract.

[0052] • : The benefits of watchtowers honestly monitoring payment channels, .

[0053] When the participants in the system remain rational, the parameters should satisfy the following constraints:

[0054] (1) : Otherwise, the watchtower cannot accept the monitoring request from the trading party.

[0055] (2) : The counterparty is unwilling to pay more bribes than the collusion.

[0056] (3) : Only when The bribe offered is greater than They only agree to conspire when there is a reward for their efforts.

[0057] Sub-step 2.1: Build the Watchtower smart contract.

[0058] The watchtower contract is actually the transaction party ( ) and two outsourced watchtowers and The signed contract allows the trading party to entrust and Monitor payment channels. The detailed steps of the contract are as follows:

[0059] (1) The Watchtower contracts are respectively and as well as and sign.

[0060] (2) 、 and Agree to the contract together and set three deadlines .

[0061] (3) Agree to pay funds to Watchtower Get the latest and most accurate CSP in a timely manner.

[0062] (4) and Need to be on deadline Before paying a deposit to the contract , otherwise the contract will be terminated and the deposit can be temporarily managed by the contract.

[0063] (5) and The latest CSP must be submitted before the deadline T2 ( and ).

[0064] (6) and The latest CSP reported separately, or on the deadline after:

[0065] (a) If and Failure to report the latest CSP, their deposit will be paid to .

[0066] (b) If and Provides the same CSP, which means and Effectively monitor payment channels, Need to and Payment of funds, deposit can be returned to and .

[0067] (c) Otherwise, go to step (7).

[0068] (7) Perform a second proofreading and use the latest CSP as :

[0069] (a) If and Both provide the correct CSP and , in addition to paying the second proofreading fee, Each watchtower must also be paid and have its deposit returned.

[0070] (b) If and All return fraudulent CSP, their deposit will be paid to ,Then A second proofreading fee will be paid.

[0071] (c) If only one watchtower returns the fraudulent CSP, the watchtower’s deposit will be paid to .also, Not only does it pay for the second proofreading, but it also pays Additional rewards are given to watchtowers that provide the correct CSP, and their deposits are refunded.

[0072] (8) If Failure to pay after the T3 deadline and , Will be required to pay according to the contract and (On the deadline CSP provided before) and refund their deposit.

[0073] Deadline in the contract ( ) is used to enforce timeliness, which prevents funds from being frozen if one party refuses to execute the contract.

[0074] Sub-step 2.2: Construct the collusion smart contract.

[0075] The collusion contract aims to break the equilibrium of the watchtower contract. The detailed steps of the contract are as follows:

[0076] (1) The conspiracy contract is made by and Signed. Assume that the conspiracy is Initiated.

[0077] (2) and Agree to send fraudulent CSP in the watchtower contract .

[0078] (3) and A deposit must be paid separately when signing a collusion contract and , these two deposits are temporarily managed by the collusion contract.

[0079] (4) and Must be on the deadline ( ) before the date of the contract. Otherwise, the contract will be terminated and the deposit will be refunded.

[0080] (5) When the watchtower contract terminates, the following operations will be performed on the deposit balance held in the collusion contract:

[0081] (a) If and If both parties follow the collusion contract, the deposit and Will be returned to and .

[0082] (b) If Delayed performance of contract, deposit Will be returned to , You will lose your deposit .

[0083] (c) If Breach of contract, deposit Will be returned to , You will lose your deposit .

[0084] (d) If and If both parties breach the contract, the deposit and Will be refunded to W1 and W2 respectively.

[0085] The collusion agreement must be signed on the deadline Before signing, because and Need to be on deadline The latest CSP was sent before.

[0086] Sub-step 2.3: Construct the fraud smart contract.

[0087] Fraudulent contracts are caused by the counterparty ( ) and a watchtower. The contract details are as follows:

[0088] (1) Fraudulent contract by and sign.

[0089] (2) Agree to send CSP in the watchtower contract .

[0090] (3) and A separate deposit is required when signing a fraudulent contract and These two deposits are temporarily managed by the fraud contract.

[0091] (4) and Must be on the deadline and < < Otherwise, the contract will be terminated and the deposit will be refunded.

[0092] (5) When the watchtower contract terminates, the following actions will be performed on the deposit balance held in the fraud contract:

[0093] (a) If Follow the fraud contract and send the latest CSP in the watchtower contract , then the deposit and Will be returned to and .

[0094] (b) If Failure to comply with fraudulent contracts, deposits Will be returned to .

[0095] When there is no collusion contract, and PCN is usually monitored and the latest CSP is sent However, if Want to cheat in a contract Get extra rewards, Can pretend to Then, when Sending fraudulent CSP in the watchtower contract hour, Can betray the collusion contract and send CSP .therefore, will be punished and lose the deposit g in the collusion contract. In short, You can choose whether to collusion.

[0096] Sub-step 2.4: Construct an anti-collusion contract.

[0097] The anti-collusion contract allows a watchtower that reports to a transacting party to secretly betray the other party while pretending to follow the conspiracy. Without this exemption, watchtowers will not voluntarily report the conspiracy. The detailed steps of the contract are as follows:

[0098] (1) Anti-collusion contracts are made by 、 Signed. Assuming the conspiracy is made by Initiated, conspired by Report. At this time, 、 Requires a signed Watchtower contract.

[0099] (2) Enter into an anti-collusion contract only with the watchtower that first reported the collusion, and agree to compensate the watchtower for lost deposits in the contract if appropriate.

[0100] (3) Need to pay This is equivalent to a deposit of The maximum possible loss in a watchtower contract is Deposit required , which is equivalent to the possible cost of secondary proofreading. These deposits will be temporarily managed by the anti-collusion contract.

[0101] (4) The contract should be concluded on the expiration date. Otherwise, the contract will be terminated and any deposit paid will be refunded.

[0102] (5) The latest CSP must be reported On the expiration date of this contract Before.

[0103] (6) You need to apply for a second proofreading and perform the following operations based on the judgment results:

[0104] (a) If there is no fraudulent CSP in the watchtower contract, then refund Deposit , and will Deposit Pay to .

[0105] (b) If Send the correct CSP in the watchtower contract ,and Send fraudulent CSP in the watchtower contract and anti-collusion contract respectively And report to CSP .Then, and Will compensate separately and .

[0106] (c) If and All send fraudulent CSP in the watchtower contract ,and Reporting CSP in anti-collusion contracts .Then, Deposit Will be refunded, reward Will pay to .

[0107] (d) Otherwise, and Will be paid separately and .

[0108] (7) If Report the latest CSP in this contract , and exceeded the deadline , all deposits will be returned to .also, The following conditions must also be met:

[0109] (a) Intend to Conspiracy and the making of a conspiracy contract.

[0110] (b) Before signing the conspiracy agreement Report collusion. Optionally submit collusion evidence, such as the address of the collusion contract and the fraudulent CSP sent during the collusion .

[0111] (c) An anti-collusion contract needs to be signed before a collusion contract is signed.

[0112] Before reporting, Need to wait Initiate collusion and sign the collusion contract. Otherwise, if the collusion is reported to the transaction party without collusion, will be in a false reporting situation because The correct CSP will be provided in the watchtower contract In a distributed watchtower scenario, rational It is unlikely that additional rewards can be obtained through false reporting (e.g., reporting some fabricated evidence) because have no idea Whether an anti-collusion contract has also been signed. Therefore, distributed watchtowers can impose mutual restrictions and effectively prevent false reports.

[0113] Step 3: Sequential equilibrium game based on multi-party smart contracts. This step ensures that the system's multi-party complex game process can converge to a sequential equilibrium game through multi-party smart contracts, and uses a game tree to visualize the equilibrium point of the game. The game process based on multi-party smart contracts contains a total of 6 possibilities, which can be described by 6 game trees (such as Figure 3-Figure 8 ). The details are as follows:

[0114] The first game: This game process is dominated by the watchtower contract. The specific process is as follows Figure 3 As shown, the participants are , the action set is ,in yes and The correct CSP returned before the deadline, yes The fraudulent CSP given when collusion occurs (obviously ).besides, express Any other results that may be returned. The first game contains 5 information sets: , , , , , where 𝑣 is the sending CSP choice made by watchtower 1, 𝑢 is the sending CSP choice made by watchtower 2, 𝑞 is a non-terminal selection node, and l is a terminal node. In addition, 、 、 is the payment function, and the payments of each party are listed next to the terminal nodes.

[0115] if and According to formula (1), the first game can be guaranteed to have a unique sequential equilibrium. , and the game ends at the terminal node Finish.

[0116]

[0117] The second game: This game process is dominated by the watchtower contract and the collusion contract. The specific process is as follows Figure 4 As shown, the participants are , the action set is ,in Refusal to initiate conspiracy, express consent to initiate the conspiracy, Refusal to collude, The second game contains 7 information sets: , , , , , .also, 、 、 is the payment function, and the payments of each party are listed next to the terminal nodes.

[0118] In a conspiracy contract, Towards Bribery to initiate the conspiracy and satisfy ,in is the cost paid by the watchtower to monitor the PCN. and All send fraudulent CSP , then the conspiracy is successful. In addition, Bribes need to be paid , whose return is .if Unable to initiate collusion, the reward is According to the conspiracy contract, ,therefore A conspiracy will be initiated. In addition, and A deposit must be paid for this contract , and prove that ,in The standard ensures that:

[0119] (1) The payoff to a conspirator who betrays the conspirator will be lower than that to a conspirator who does not betray the conspirator.

[0120] (2) Those who participate in the conspiracy will receive higher rewards than those who do not participate in the conspiracy.

[0121] if and According to formula (2), the second game can be guaranteed to have a unique sequential equilibrium , the game will be played at the terminal node Finish.

[0122]

[0123] The third game: This game is dominated by the fraud contract and the watchtower contract. The specific process is as follows Figure 5 As shown, assuming You can reasonably choose whether to collude based on the payment situation. Choose not to When collusion occurs, the third game is entered. The participants are , the action set is The third game involves five information sets: , , , , .also 、 、 is the payment function, and the payments of each party are listed next to the terminal nodes.

[0124] if According to formula (3), the third game can be guaranteed to have a unique sequential equilibrium , the game will be played at the terminal node Finish.

[0125]

[0126] The fourth game: This game process is dominated by fraud contracts, collusion contracts and watchtower contracts. The specific process is as follows Figure 6 As shown, assuming You can reasonably choose whether to collude based on the payment situation. Select and When collusion occurs, the fourth game is entered. The participants are , the action set is The fourth game involves five information sets: , , , , .also 、 、 is the payment function, and the payments of each party are listed next to the terminal nodes.

[0127] (a) If and According to formula (4), the fourth game can be guaranteed to have a unique sequential equilibrium ,and CSP will be sent and betray the collusion contract, the fourth game will be at the terminal node Finish.

[0128]

[0129] (b) If and According to formula (5), the fourth game can be guaranteed to have a unique sequential equilibrium ,and CSP will be sent and betray the collusion contract, the game will be at the terminal node Finish.

[0130]

[0131] The fifth game: This game is dominated by the watchtower contract, fraud contract and anti-collusion contract. The specific process is as follows Figure 7 As shown, at this time, the watchtower will not initiate collusion, or the collusion will be rejected. The participants in the game process are , the action set is ,in Not reporting, Indicates that the latest CSP reported is , Indicates that the latest CSP is not reported The fifth game consists of 14 information sets: , , , , , , , , , , , , , .also 、 、 is the payment function, and the payments of each party are listed next to the terminal nodes.

[0132] if and According to formula (6), the fifth game can be guaranteed to have a unique sequential equilibrium , the game will be played at the terminal node Finish.

[0133]

[0134] In summary, the first five games analyze the sequential equilibrium of rational participants in the watchtower contract, collusion contract, fraud contract and anti-collusion contract scenarios respectively. and 、 and An employment contract between and Gain benefits by monitoring payment channels. In order to destroy the former equilibrium, the collusion contract is designed as and Collusion between parties to obtain additional benefits outside of the watchtower contract. Furthermore, a fraud contract is a collusion between a counterparty and a malicious watchtower, where the counterparty intends to cooperate with the malicious watchtower to obtain further additional income. Finally, an anti-collusion contract is added to the game to effectively combat fraud contracts, forcing malicious watchtowers to betray their previously signed contract by exempting them from penalties.

[0135] The sixth game is dominated by the watchtower contract, collusion contract, fraud contract and anti-collusion contract. The specific process is as follows: Figure 8 As shown. First assume Initiate collusion and choose strategy first. If W1 does not initiate collusion, or initiates collusion but If , there is no collusion contract in the game, and the game will enter the fifth game. Agree with Collusion, in this game, will Report collusion and sign an anti-collusion agreement. In addition, if and Signed an anti-collusion agreement, No collusion contract will be signed and the game will enter the sixth game. The game participants are , the action set is , the sixth game contains 7 information sets: , , , , , .also, 、 、 is the payment function, and the payments of each party are listed next to the terminal nodes.

[0136] if 、 、 and According to formula (7), the sixth game can be guaranteed to have a unique sequential equilibrium , the game will be played at the terminal node Finish.

[0137]

[0138] In summary, since multi-party smart contracts can ensure that the system's complex multi-party game processes can converge to sequential equilibrium games, rational participants will not rashly initiate collusion in order to maximize their own interests. Otherwise, they will not only fail to obtain normal benefits, but will also pay more fines for this.

[0139] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention. It should be understood that the embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. After reading the present invention, modifications to various equivalent forms of the present invention made by those skilled in the art fall within the scope defined by the claims appended to this application.

Claims

1. A blockchain multi-party smart contract method for cryptocurrency payment channel networks, characterized in that: The method comprises the following steps: Step 1: System initialization. This system consists of three roles: watchtowers, transactors, and counterparties. Watchtowers are responsible for real-time monitoring of the payment channel network and regularly updating channel status certificates. Transactors are responsible for hiring watchtowers and sending channel status certificates to them. Counterparties maximize their own interests by selectively signing smart contracts and sending channel status certificates. In this system, there is a risk of collusion between counterparties and watchtowers, and between watchtowers themselves, to gain additional benefits. Step 2: Establish four smart contracts to defend against possible collusion attacks in various outsourced watchtower scenarios. The specific steps are as follows: Sub-step 2.1: Construct a watchtower smart contract. The watchtower smart contract is signed by the transaction party and two watchtowers, allowing the transaction party to entrust the watchtower to monitor the payment channel. Sub-step 2.2: Construct a collusion smart contract. The collusion contract is signed between two watchtowers and aims to break the equilibrium of the watchtower contract. Sub-step 2.3: Construct a fraud smart contract. The fraud contract is signed by the counterparty and a watchtower to prevent a watchtower from colluding with the counterparty to obtain additional benefits by betraying another watchtower. Sub-step 2.4: Construct an anti-collusion contract. The transaction parties only sign the anti-collusion contract with the watchtower that first reports the collusion, ensuring that the watchtower that reports the collusion will not be punished by the watchtower contract. Step 3: Based on the sequential equilibrium game of multi-party smart contracts, the operation process of the watchtower and the employer in the system, that is, the transaction party and the transaction counterparty, is a complex game process. The multi-party smart contract ensures that the process can obtain a unique sequential equilibrium.

2. The blockchain multi-party smart contract method for a cryptocurrency payment channel network according to claim 1, characterized in that: Sub-step 2.1: Build the Watchtower smart contract as follows: The watchtower contract is actually the transaction party ( ) and two outsourced watchtowers and The signed contract allows the trading party to entrust and To monitor the payment channel, the detailed steps of the contract are as follows: (1) The Watchtower contracts are respectively and as well as and sign, (2) 、 and Agree to the contract together and set three deadlines , (3) Agree to pay funds to Watchtower Get the latest and most accurate CSP in a timely manner, (4) and Need to be on deadline Before paying a deposit to the contract , otherwise the contract will be terminated and the deposit can be temporarily managed by the contract, (5) and The latest CSP must be submitted before the deadline T2, and , (6) and The latest CSP reported separately, or on the deadline after: (a) If and Failure to report the latest customer service provider, their deposit will be paid to , (b) If and Provides the same CSP, which means and Effectively monitor payment channels, Need to and Payment funds, deposit returned to and , (c) Otherwise, go to step (7), (7) Perform a second proofreading and use the latest CSP as : (a) If and Both provide the correct CSP and , in addition to paying the second proofreading fee, Each watchtower must also pay and return its deposit, (b) If and All return fraudulent CSP, their deposit will be paid to ,Then The second proofreading fee will be paid, (c) If only one watchtower returns the fraudulent CSP, the watchtower’s deposit will be paid to ,also, Not only does it pay for the second proofreading, but it also pays Provide additional rewards to watchtowers that provide correct CSP and return their deposits, (8) If Failure to pay after the T3 deadline and , Will be required to pay according to the contract and , on the deadline Provide CSP before and return its deposit, Deadlines in contracts, , used to enforce timeliness, which prevents funds from being frozen if one party refuses to execute the contract.

3. The blockchain multi-party smart contract method for a cryptocurrency payment channel network according to claim 1, characterized in that: Sub-step 2.2: Construct the collusion smart contract as follows: The collusion contract aims to break the equilibrium of the watchtower contract. The detailed steps of the contract are as follows: (1) The conspiracy contract is made by and Signed, assuming the conspiracy is made by Initiated, (2) and Agree to send fraudulent CSP in the watchtower contract , (3) and A deposit must be paid separately when signing a collusion contract and , these two deposits are temporarily managed by the collusion contract, (4) and Must be on the deadline Before paying the above deposit, Otherwise, the contract will be terminated and the deposit will be refunded. (5) When the watchtower contract terminates, the following operations will be performed on the deposit balance held in the collusion contract: (a) If and If both parties follow the collusion contract, the deposit and Will be returned to and , (b) If Delayed performance of contract, deposit Will be returned to , You will lose your deposit , (c) If Breach of contract, deposit Will be returned to , You will lose your deposit , (d) If and If both parties breach the contract, the deposit and Will be refunded to W1 and W2 respectively, The collusion agreement must be signed on the deadline Before signing, because and Need to be on deadline The latest CSP was sent before.

4. The blockchain multi-party smart contract method for a cryptocurrency payment channel network according to claim 1, characterized in that: Sub-step 2.3: Construct a fraud smart contract as follows: Fraudulent contracts are caused by the counterparty ( ) and a watchtower. The contract details are as follows: (1) Fraudulent contract by and sign, (2) Agree to send CSP in the watchtower contract , (3) and A separate deposit is required when signing a fraudulent contract and These two deposits are temporarily managed by the fraud contract. (4) and Must be on the deadline and < < Otherwise, the contract will be terminated and the deposit will be refunded. (5) When the watchtower contract terminates, the following actions will be performed on the deposit balance held in the fraud contract: (a) If Follow the fraud contract and send the latest CSP in the watchtower contract , then the deposit and Will be returned to and , (b) If Failure to comply with fraudulent contracts, deposits Will be returned to , When there is no collusion contract, and PCN is usually monitored and the latest CSP is sent , however, if Want to cheat in a contract Get extra rewards, Pretend to be Conspiracy, then, when Sending fraudulent CSP in the watchtower contract hour, Betray the collusion contract and choose to send CSP ,therefore, Will be punished and lose the deposit g in the collusion contract. In short, Choose whether to collusion.

5. The blockchain multi-party smart contract method for a cryptocurrency payment channel network according to claim 1, characterized in that: Sub-step 2.4: Construct an anti-collusion contract, as follows: The anti-collusion contract allows a watchtower that reports to a transaction party to secretly betray the other party while pretending to follow the collusion. Without this exemption, the watchtower will not voluntarily report the collusion. The detailed steps of the contract are as follows: (1) Anti-collusion contracts are made by 、 Signed, assuming the conspiracy consists of Initiated, conspired by Report, at this time, 、 Need to have signed the Watchtower contract, (2) Enter into an anti-collusion contract only with the watchtower that first reported the collusion, and agree to compensate the watchtower for lost deposits in the contract if appropriate, (3) Need to pay This is equivalent to a deposit of The maximum possible loss in a watchtower contract is Deposit required , which is equivalent to the possible secondary proofreading cost, these deposits will be temporarily managed by the anti-collusion contract, (4) The contract should be completed on the expiration date Otherwise, the contract will be terminated and any deposit paid will be refunded. (5) The latest CSP must be reported On the expiration date of this contract Before, (6) You need to apply for a second proofreading and perform the following operations based on the judgment results: (a) If there is no fraudulent CSP in the watchtower contract, then refund Deposit , and will Deposit Pay to , (b) If Send the correct CSP in the watchtower contract ,and Send fraudulent CSP in the watchtower contract and anti-collusion contract respectively And report to CSP ,Then, and Will compensate separately and , (c) If and All send fraudulent CSP in the watchtower contract ,and Reporting CSP in anti-collusion contracts ,Then, Deposit Will be refunded, reward Will pay to , (d) Otherwise, and Will be paid separately and , (7) If Report the latest CSP in this contract , and exceeded the deadline , all deposits will be returned to ,also, The following conditions must also be met: (a) Intend to Conspiracy, and the making of a conspiracy contract, (b) Before signing the conspiracy agreement Report collusion, Choose to submit collusion evidence, including the address of the collusion contract and the fraudulent CSP sent during the collusion , (c) An anti-collusion contract must be signed before a collusion contract. Before reporting, Need to wait Initiate collusion and sign the collusion contract, otherwise, if there is no collusion, report the collusion to the transaction party, will be in a false reporting situation because The correct CSP will be provided in the watchtower contract , in the distributed watchtower scenario, rational It is unlikely that additional returns can be obtained through false reporting because have no idea Whether an anti-collusion contract is also signed, so that distributed watchtowers impose mutual restrictions, effectively preventing false reports.

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