【作者】 张鑫；

【导师】 孙敏；

【作者基本信息】 山西大学 ， 计算机技术， 2025， 硕士

【摘要】 区块链技术的核心在于共识机制,共识机制是保障整个区块链系统持续运行的关键。然而PoS(Proof of Stake,权益证明)面临不活跃节点通过长期持有权益累积币龄,增加成为出块节点可能性的问题。DPoS(Delegated Proof of Stake,委托权益证明)存在持币人将投票权委托给少数节点导致权力过度集中,对恶意节点的惩罚力度有限,难以有效抵御女巫攻击的问题。而PoC(Proof of Contribution,贡献值证明)作为一种新颖的共识机制,以贡献值的大小作为出块依据,符合“按劳分配、多劳多得”的价值理念,但在交易中存在通过制造虚假贡献值提高获得记账权概率的问题。为了解决上述问题,本文将权益证明与委托权益证明分别与贡献值证明结合,分别设计了PoCaS(Proof of Contribution and Stake,基于贡献值与权益值的混合共识机制)和DPoSaC(Delegated Proof of Stake and Contribution,基于贡献值和委托权益证明的混合共识机制),具体工作如下:针对权益证明的币龄累积攻击问题和贡献值证明的虚假贡献值问题,提出了基于贡献值与权益值的混合共识机制,一定程度上解决了上述问题,还可以提高节点积极性。首先,引入亲密度来反映节点之间是否存在制造虚假贡献值的情况,统计过亲密行为次数算出声誉值,再结合贡献值,得出节点的声誉贡献值。其次,将节点按照声誉贡献值降序排序后再利用斐波那契数列分组法分组得到活跃指数。最后,综合节点所持权益和活跃指数对各节点设定不同的挖矿难度,各节点通过PoW(Proof of Work,工作量证明)竞争出块。实验结果表明,该共识机制可以使虚假贡献值节点的出块率最多降低80%,使币龄累计节点获得记账权的次数最多降低89%,并且一定程度提高节点的积极性。针对委托权益证明的权利中心化问题,结合的贡献值证明,提出了基于贡献值和委托权益证明的混合共识机制,一定程度上解决了上述问题,还可以增大对于恶意节点的惩罚力度。一方面,引入黑名单环节,一次投票结束后,若当选节点存在非法交易行为,允许未入选节点进行举报,若情况属实,则非法节点会进入黑名单,影响其信誉值,一定程度避免了一些非法交易行为,提高系统安全性。另一方面,为每个节点设定投票权重,从权益值、贡献值、信誉值三个方面考量节点,使得投票结果更具可靠性。实验结果表明,该共识机制可以使得通过非法交易获得高贡献值和高权益值的节点的出块率一定程度上降低,并且提高诚实节点的占比。基于上述研究内容提出并实现了基于区块链的房地产交易系统,同样考量了用户的贡献值,在每一次房产交易前,系统都会根据用户的贡献值进行风险评估。只有达到一定标准的用户才能进行交易。这一机制有效地限制了短期大量购买房产的炒房行为,维护了房地产市场的健康稳定发展。首先对交易平台进行了系统设计和说明,并对主要功能模块进行说明;其次对系统中的各项功能进行测试,结果表明系统可以正常运行,能够实现房屋的购买等功能。更多还原

【Abstract】 The core of blockchain technology lies in its consensus mechanism,which is the key to ensuring the continuous operation of the entire blockchain system.However,PoS(Proof of Stake)faces the problem of inactive nodes accumulating coin age through long-term holding of equity,increasing the possibility of becoming block making nodes.DPoS(Delegated Proof of Stake)has problems such as excessive concentration of power caused by holders entrusting their voting rights to a few nodes,limited punishment for malicious nodes,and difficulty in effectively resisting witch attacks.As a novel consensus mechanism,PoC(Proof of Contribution)conforms to the value concept of"distribution according to work,more work,more pay".However,there are problems in increasing transaction volume and creating false contribution values to improve the probability of accounting rights through raising funds in transactions.In order to solve the above problems,this paper combines proof of stake and delegated proof of stake with contribution value proof,and designs PoCaS(Proof of Contribution and Stake,a hybrid consensus mechanism based on contribution value and equity value)and DPoSaC(Delegated Proof of Stake and Contribution,a delegated proof of stake based on contribution value),respectively.The specific work is as follows:To address the issues of coin age accumulation attacks and false contribution value problems in proof of stake,a hybrid consensus mechanism based on contribution value and equity value is proposed,which to some extent solves the above problems and can also improve node motivation.Firstly,intimacy is introduced to reflect whether there is a situation of creating false contribution values between nodes.The reputation value is calculated by counting the number of intimate behaviors,and then combined with the contribution value,the reputation contribution value of the nodes is obtained.Secondly,the nodes are sorted in descending order of reputation contribution value and then grouped using the Fibonacci sequence grouping method to obtain the activity index.Finally,different mining difficulty levels are set for each node based on their equity and activity index,and each node competes for blocks through Proof of Work(PoW).The experimental results show that this consensus mechanism can reduce the block rate of nodes with false contribution values by up to 80%,reduce the number of times nodes with accumulated coin age obtain accounting rights by up to 89%,and to some extent improve node motivation.In response to the issue of centralization of rights in delegated equity proof,a contribution value based delegated equity proof is proposed,which to some extent solves the above problems and can also increase the punishment for malicious nodes.On the one hand,the introduction of a blacklist process allows non selected nodes to report illegal trading activities after a vote.If the situation is true,the illegal nodes will be blacklisted,affecting their reputation and to some extent avoiding some illegal trading activities,thus improving system security.On the other hand,setting voting weights for each node,considering nodes from three aspects: equity value,contribution value,and reputation value,makes voting more reliable.The experimental results show that this consensus mechanism can reduce the block generation rate of nodes that obtain high contribution and equity values through illegal transactions to a certain extent,and increase the number of honest nodes.Based on the above research content,a blockchain based real estate transaction system was proposed and implemented,which also considers the contribution value of users.Before each real estate transaction,the system conducts risk assessment based on the user’s contribution value.Only users who meet certain standards can conduct transactions.This mechanism effectively restricts short-term large-scale real estate speculation and maintains the healthy and stable development of the real estate market.Firstly,the prototype system was designed and described as a whole,and the main functional modules were explained;Secondly,various functions in the system were tested,and the results showed that the system can operate normally and achieve functions such as purchasing houses.更多还原