Blockchain is a decentralized,untrustworthy distributed database technology.The database is collectively maintained by all the nodes involved in the system,and has the features of decentralization,tamper-resistance,trans-parentness and security.The emergence of blockchain technology thanks to the Bitcoin applications.Blockchain is the underlying technique support of Bitcoin system and is the fundament of the Bitcoin system.Since Blockchain technology is a promising technology,the key technologies,components,principles,limitations,applications and prospect were introduced,and the related research issues was discussed.

With the rise of Bitcoin,Ethernet,Hyperledger and so on,blockchain has been paid more and more attention.Blockchain is the product of many technologies,and the consensus algorithm is an important standard to adjudicate a blockchain system.The adopted consensus algorithm should be different from the blockchain system to another for the different features.Different consensus algorithms have their own advantages,but they also have shortcomings.Currently,efficiency problem is one of the main problems faced by the consensus algorithm in the blockchain.In order to improve the efficiency,the potential optimization scheme of the consensus algorithm in the blockchain was introduced.Then,the dBFT consensus algorithm commonly used in the alliance chain was taken as the research object,and through combining with the aggregation signature and the bilinear mapping technology,the consensus process was modified.At last,compared with the original scheme,the space complexity of the signature in blockchain system can be effectively reduced with the aggregated dBFT.

The power system is evolving from Smart Grid to Energy Internet with the development of new energy technologies and Internet technologies.Distributed energy resources will become the main primary energy in the future Ener-gy Internet.In this situation,virtual power plant technology plays an important role in the convergence of distributed power generation resources and the establishment of virtual power resource transactions.As a new distributed computing paradigm,blockchain has the characteristics of security,transparency and decentralization.This paper proposed a blockchain based virtual power plant model for the future Energy Internet driven by real-time electricity price.The coordinated control method of virtual power plant and the independent grid connected behavior of distributed energy resources are organically linked by the incentive mechanism of blockchain,so as to realize the distributed dispatching calculation of virtual power plant.Simulation results show that the proposed model meets the grid-connected requirements of high penetration,high freedom,high frequency and high speed of distributed energy resources in the future Energy Internet.

Blockchain is a kind of distributed ledger system with peer-to-peer network,which has drawn widespread attention because of its characteristics such as decentralization,non-tempering,security and credibility.In a blockchain system,some nodes have the Byzantine errors such as operational errors,network latency,system crashes,malicious attacks,and so on.The existing consensus algorithms are less tolerant to the Byzantine nodes in the blockchain,and the scalability of the blockchain system is poor.In order to solve these problems,this paper proposed a Byzantine consensus algorithm based on Gossip protocol,which allows the system to tolerate less than half of the nodes as the Byzantine node and achieve the fault-tolerant performance of XFT consensus algorithm.This paper proved that the algorithm can reach consensus in a distributed system with Byzantine defects from the agreement,correctness and termination.At the same time,the system adopts the uniform data structure,and thus has better scalability and facilitates the right node to identify the Byzantine nodes in the blockchain system.In this algorithm,the proposed node is shifted with the change of the length of blockchain,so that all nodes in the system are in the same position,thus avoiding the single point of failure problem,and making the system have better dynamic load balancing performance.

Data right confirmation has always been one of the most challenging problems in big data trading.Traditional means of right confirmation adopt the model of submitting the ownership evidence and expert reviewing,but they lack technological credibility and there are some uncontrollable factors such as potential tampering.In order to solve these problems,a strongly operational confirmation scheme is urgently needed.This paper put forward a new big data right confirmation scheme based on the technologies of blockchain and digital watermarking.Firstly,the auditing center and watermarking center are brought in to separate the duties of the integrity auditing of big data and watermarking generation.Secondly,using provable data possession technique and sampling technique,the lightweight audit of the integrity of big data is realized.Thirdly,the special security properties of digital watermarking technology are used to confirm the origin of big data.Finally,in the light of the integrity and persistence of evidence involved in the right confirmation,the native features of blockchain,such as the shared ledger,are used to implement strong consistency of the right confirmation result and relevant evidence.Correctness and security analysis results show that the proposed scheme can provide a new technical solution for the definition of ownership of big data.

The eclipse attack against the blockchain has the characteristics of concurrency and concealment,and often relies on multi-node to collaboratively complete the attack of monopolizing victim’s network connections.Correspon-dingly,the computer immune system has the characteristics of distribution,self-learning and strong adaptive ability.To detect whether the blockchain suffers from eclipse attacks,this paper proposed a new immunity based model to detect eclipse attacks on blockchain.At the same time,this paper established the architecture of the detection model,and pre-sented the formal definitions of each element and the execution processes of each module in this model.The simulated experiments were carried out according to the proposed detection model.The experimental results show higher accuracy and efficiency of this model.

As the value of Bitcoin continuously rises,the blockchain technology applied behind it has promptly drawn widespread attention throughout the world,and it has also attracted the attention of governments at the same time.In particular,some countries,represented by the United States,under the support of the governments and the power institutions,have begun to try to apply this technology in various aspects,including the construction of specific information platforms,the operation of equipment supplies,and the control of systems.They think that the features including distribution,traceability and difficult tampering,etc of this technology could give full play to advantages of many aspects such as anonymous data collection,data integrity verification,interconnected communication of intelligent equipments,etc.In the meantime,the government institutions of many countries still maintain a cautious attitude towards the application of blockchain technology and they think that this technology is still faced with lots of problems including security and the universality of application,etc.Through the introduction and analysis of applications of the blockchain technology of government departments,the challenges confronted by current blockchain technology in the applications of government departments were pointed out.Lastly,for these problems,corresponding solutions were brought forward through combing the existing work in the academic field.

At present,blockchain systems,represented by Bitcoin and Ethereum,are becoming more and more mature,and blockchain technology has become a hot topic in academic and industrial circles.However,in practical applications,these systems are generally faced with tough problems such as simple query function and low query performance due to the limitation of data storage scheme.This paper presented the survey and prospect of the research progress on data storage and query technology of blockchain systems.First,the data storage mechanism and query processing strategy used in current popular blockchain systems were introduced .Then,two methods of extending query processing functions on the existing system were introduced in details.The features of their query efficiency,write performance optimization,storage space occupancy,data security and availability were compared and analyzed in detail.Finally,the trend of the query technology development in the future block chain system was analyzed,and the main research direction was discussed and explored.

Aiming at the problem of identity management in network space,this paper analyzed a universal identity ma-nagement authentication model based on blockchain.First,the definitionand requirements of identity management in network space were outlined,and development experience and early attempts were reviewed.Then,the advantages and disadvantages of the blockchain and some kinds of proof of concepts in identity management were analyzed.Next,based on opening analysis,a general blockchain identity management model and each module were analyzed.Finally,the mature ShoCard company’s application scene and DIMS (Decentralized Identity management system) were analyzed and compared,and the prospect of the future development was put forword.

Blockchain is the technology behind Bitcoin,with the characteristics of decentralization,non-tampering and retrospective.Blockchain has been gradually applied in financial,digital rights,notarization,networking,document stora-ge and other fields,and obtained great achievements.Blackchain has become a more and more popular research area like AI (Artificial Intelligence),Big Data and Cloud Computing.AI bases on massive datasets and powerful computing ability,and Blockchain can be well integrated into AI to promote it’s rapid development.On the basis of introducing the concept and working mechanism of Blockchain,this paper mainly introduced the influence of Blockchain technology on AI,analyzed the application feasibility of Blockchain in AI,and finally put forward the prospect.

In recent years,with the development of the block chain technology,it has received extensive attention.It is generally regarded as an important tool to solve the problem of data security.RFID big data is important source of data in the Internet of things,and the security requirements for data are also very high.Data tracing is one of the important applications of RFID networking technology,it is widely used in original traceability of agricultural products,raw materials,industrial production and consumer goods and parts traceability,security and other aspects.Block chain plays an important role in improving the safety of big data source.This paper presented a RFID data source security model based on block chain technology,and block chain technology is used in the tracing process of RFID data,the formation of multi information transparency,sharing,participation and fidelity in the traceability chain.The block chain books are formed in production,processing,marketing and other aspects of the establishment of RFID tracing goods,the whole chain traceability path RFID big data is established,to end users,so as to realize the safety management of the traceability of RFID big data.

Credit is an intangible asset.Good credit record can not only bring a higher loan success rate,a lower borrowing rate,but also can make people enjoy the convenience brought by credit services.In the future,credit bonus will be highlighted,but it is also accompanied by problems,such as leakage of personal privacy,alteration of credit data,and unclear legal borders for the commercialization of big data credits.In order to create a healthy Internet credit ecological environment,this paper first summarized the existing problems in the existing credit information platform,discussed and analyzed the feasibility of adopting emerging technologies to solve these problems,and then incorporated a blockchain technology to design a kind ofmulti-source data sharing framework for supporting future credit reference system. Based on the multi-source data sharing of blockchains,abig data credit platform of multi-source heterogeneous data fusion was established using artificial intelligence,data mining,and smart contracts.Taking internet lending as an example,a decentralized lending application based on the big data credit platform was designed.

This paper stated an instruction transmission and tracing pattern in digitized command-and-control business.A typical digitized command-and-control system generally runs in a peer-to-peer network,in which each transaction of interactive instructions should be well recorded.This paper proposed a blockchain-based solution to implement efficient transmission and tracing of significant transactions which could be precisely defined by system designers.With nature attributes of encryption,decentralization and tamper resistance,blockchain-based solution focuses more on data consistency,transaction timeliness and information security.Prime events of command-and-control interactive instructions between master nodes,slave nodes and witness nodes of instruction would be completely transmitted and sequentially appended to traceable records data blocks in restraint of consensus mechanism.

In the blockchain system based on the Byzantine Fault Tolerance (BFT) protocol,the efficiency and perfor-mance of system are poor,which limited the application and development of blockchain.A system solution of supporting transaction dispatching and event handling based on multiple blockchains was proposed.In the solution,the system is divided into application clients,handling system and blockchains.Application clients are used to send out transaction requests and receive the events which are interested in.Every blockchains are used to internally handle transaction requests and events.The handling system is adaptive to the system of variable number of blockchain and the system of immutable number of blockchain.Two polices of selecting blockchain,including mapping relationship table and hash consistency alogorithm,are designed.According to the load balance,monotonicity and consistency,both of these two policies dispatch transactions based on the service type and the internal ID of service type.Every blockchain set up the one-to-one correspondence with transaction calling client,event and message streaming client.Every application client sents out the transaction requests and receives the transaction results by interacting with transaction application calling ser-ver,transaction application event connection server and event message streaming server.Transaction dispatcher and event handler were designed in detail,and basic test and verification were made for the whole system solution.

Although the digital media advertising industry represented by the internet advertising has rapidly developed in recent years,some urgent problems are continuously emerging,such as the opaque process of digital media adverti-sing,falsified feedback data,low efficiency caused by multi-level agency,and advertisers’ resources and funds are wasted without knowing statistical response.Blockchain technology provides a possible solution with a decentralized trusted P2P distributed network.Using the technologies such as Blockchain and smart contract,this paper attempted to construct an online advertising model via Blockchain which possesses some extraordinary characteristics like distributed P2P network,decentration,non-repudiation,tamper-resistant,transparency in trades,traceability and trusted consensus mechanism,so as to explore a new advertising commercial ecosystem,thus providing a safe,unconstrained,efficient,automated and intelligent electronic marketplace for advertisers and other advertising practitioners.In the combination of advertising practice and Blockchain technologies,this paper also depicted a complete running process of online adverti-sing model via Blockchain.At last,this paper gave some prospects of smart contracts and business models,as well as further combination with other mature technologies.

In recent years,more and more privacy protection requirements have been put forward for identity management systems and user-centric self-sovereign identity.As an important means to solve privacy protection problems,blockchain is used by more and more applications.Aiming at the problem of privacy protection in blockchain applications,firstly,this paper studied the privacy protection strategies of mainstream encrypted currencies,including anonymous processing of sender,receiver,content and other links,setting of blockchain access right,innovative methods such as side chain and payment channel,classified storage of data,etc.Then,the efficiency,emphasis and application prospect of each privacy protection strategy were analyzed.Specially,the importance of zero knowledge proof to distributed application based on blockchain was analyzed.Finally,this paper introduced and analyzed the privacy protection strategies in smart contracts,identity management,supply chain and other practical fields,and put forward the prospects of future direction.

In the information age,data generated from all walks of life has multiplied.These data have the characteristics of enormous quantity,complicated structure and difficulty to manage.Blockchain,as a new emerging technology,compared with traditional data management methods,owns the advantages of decentralization,trustlessand data encryption.Also,it can solve the data management issues smoothly in big data application.This paper focused on situation of application blockchain technology in four parts of personal data management,digital property protection,IoT communication and medical data sharing.Moreover,some difficult problems in each big data application were discussed and some novel solutions for above problems based on blockchain technology were summarized.Finally,this paper pointed out some important development directions of future blockchain applications in big data field.

Under the background of big data,the control and privacy of data information have become a concern.However,existing computation models mostly rely on the third-party institution.Because the incompliance and the information control of the third party cause that information security cannot be guaranteed,more privacy problems appear.To solve this problem,this paper constructed an information sharing and secure multi-party computing model with high performance and security combining the blockchain with the secure multi-party computation,which enables users to control the data autonomously while ensuring the security of data information computing and sharing.This scheme firstly combines the on-chain storage with the off-chain storage.In this storage condition,proxy heavy encryption is used for data sharing and improved consensus algorithm is used to ensure the accuracy of nodes.Then,based on the MapReduce parallel computing framework,an improved homomorphic encryption algorithm was put forward for data processing and secure computing in cipher without decrypting the privacy data.Finally,the correctness and the security of the scheme were analyzed,and the experimental simulation was carried out.The analysis results and experimental results show that this scheme has high performance when dealing with big data and has a great improvement in operational efficiency.

Blockchain is a decentralized global distributed database leger.Smart contract is a piece of event-driven program with states that runs over blockchain systems,which can take custody over digital assets.Smart contracts running on a common platform can also implement parts of the functions of traditional applications.Development of the blockchain provides an appropriate platform for smart contract,and smart contract plays an important role on blockchain systems.With the rapid development of blockchain platforms such as Bitcoin and Ethereum,smart contracts have a good development opportunity.However,applications of smart contract are still in the early stage of development,and there are relatively few related studies.The application scenarios of smart contracts are not enough in practical application.This paper studied programming languages and implementation technologies of smart contract,discussed and explored the development status as well as challenges and future prospects.It described the characteristics of different development languages and took a comparison among them.Then,it classified blockchain systems based on the running environment of smart contract,and studied the development,deployment and running mechanism of smart contracts in various blockchain systems.Also,this paper explored the application scope of various smart contract platforms,and took a comprehensive comparison of different blockchain systems on smart contract development,community support and corresponding ecosystems.It introduced the status and challenges of smart contract research,and conducted analysis on security,scalability,and maintainability.Finally,it analyzed the development trend of blockchain and smart contract technology,and discussed the application scenarios in the future.

With the continuous development of the internet economy,more and more merchants choose to use internet terminal for account management.However,there are a series of problems such as loss of account books,tampering with data,and crisis of trust between merchants due to human factors.By sorting out the common accounting management problems in the current society,distributed storage,traceability andnon-defor mable of data,which are precisely the main features of blockchain,become the keys to solve the problems of account management.In view of the importance of the account books on transaction partners and the high degree of fit between blockchain technology and account book management,this paper proposed an inter-merchant account management model based on blockchain technology.Firstly,based on the introduction of blockchain characteristics and link between blockchain and ledger management,a structure of ledger management model is explained.Secondly,the design of transaction text format,block,smart contract and consensus are analyzed.Finally,the model is analyzed for safety and performance,and the shortcomings of model performance are analyzed.It is proved that the account book management model based on blockchain technology meets the security and performance requirements of account book management between merchants.This model provides new ideas and methods for establishing a safe and reliable transaction account management.

The technical characteristics of de-centered,de-trust,data complete and traceable of block chain provide brand-new opportunity and challenge for cloud computing.Users get computing,storage,database and other resources from the traditional centralized data center through network.There are many problems under this model,such as high operating cost,low efficiency,unsafe data storage and so on.In this paper,a de-centered cloud computing trading mechanism and method was proposed to build a cloud computing resource trading market based on block chain technology,focusing on the application of consensus mechanism in the central cloud computing trading market.Through the analysis and comparison of the popular block chain consensus algorithms (Pos,PoW,DPoS,PBFT),this paper proposed the improved practical byzantine fault-tolerant algorithm (PBFT),which is employed to optimize the disadvantages of resource waste and trust loss when the etheric square is applied to the alliance chain,so as to reduce the cost,and apply the improved algorithm to the central trading market of cloud computing resources.This paper proposed to introducte block chain technology in cloud computing resource trading,and collectively maintain a reliable distributed database by means of de-centered and de-trust.The design of a consensus mechanism based on Ethernet can build a global Internet computing power trading platform,thus realizing the elastic scalability and on-demand allocation of cloud computing resources.

This paper proposed a solution for experimental teaching fund system based on blockchain technology,it is divided into a core data network and an information disclosure network.The core data network is a distributed database composed of a series of core nodes with equal power,which is mainly responsible for data storage and input.The information disclosure network is an open network where anyone can read the complete data stored in the core data network and supervise the experimental related information,but does not have write permission.Experimental results show that decentralized algorithm and data can add a better monitoring mechanism to the traditional methods based on moral education.

At present,in the process of trust evaluation of trust model,because the sources of evaluation data are not uniform,the ability of different nodes to obtain evaluation data is different,and the recognition degree of different nodes to data is also different,the computational results are low accuracy,subjective and difficult to be used as a reference.Aiming at these problems,this paper proposed a blockchain-based peer-to-peer network trust model,named ChainTrust.The evaluation sequence graph is defined.The indirect trust weight is determined according to the reliability of the indirect trust degree of the evaluation node.Meanwhile,this paper improved the current blockchain structure,by using the Merkle Patricia tree and the binary Merkle tree to store the evaluation data,and gave the corresponding storing and reading algorithms.Simulation and analysis results show that ChainTrust can better resist a variety of malicious attacks,thus reducing the impact from the collusion attack,changing the sensitivity of the model by adjusting the model parameters.Therefore,ChainTrust is effective and has high flexibility and universality.

The power and environment monitoring system of base station realizes the functions of the whole network base station power and environment monitoring and real-time alarm by constructing the base station intelligent monitoring unit on the underlying intelligent and non-intelligent devices.Therefore,the stability and safe operation of the po-wer and environment monitoring system is a prerequisite.However,as the number of base stations increases,the system in the central server architecture mode will show problems such as increased load and traffic overload,and the many-to-one mode is prone to DoS.Security issues such as attacks and data breaches.In addition,in multi-user mode,the existing system mode cannot achieve fine-grained access control.Aiming at the above problems,combined with the unique advantages of blockchain technology in distributed architecture,this paper proposed a double blockchain power and environment monitoring system of base station architecture based on improved PBFT consensus algorithm to solve the centralization,security,expansion and other.of the existing system problems.Specifically,the system is a hierarchical architecture information system,and each layer maintains a blockchain.the system is a dual-chain blockchain system that is maintained and shared by multiple nodes.One is responsible for the flow of cross-domain information in the form of a league chain,and the control of the authority,the other is responsible for the access control of the base station device and the flow of the base station transaction information in the form of a private chain.And achieves fine-grained access control of the device through PKI system and the key management system,and the improves block header to store the permission information.Finally,the results show that compared with the existing traditional system,the system of this paper proposed has certain advantages of multi-center service,anti-DoS attack,user-based fine-grained rights management,high degree of information encryption and good scalability through the qualitative analysis.

According to the status quo of medical informationization in China,the traditional electronic data model has the following problems in information storage.Firstly,electronic data have poor standardization and slow circulation.Secondly,electronic data security and privacy are threatened.Aiming at the security problem of information storage and the sharing of information between medical information systems,combined with the consensus mechanism of blockchain,encryption mechanism and peer-to-peer network,a blockchain-based information management scheme was proposed to realize the storage and sharing of medical information,which is non-tamperable and decentralized.The consensus of the network nodes is realized through the improved Byzantine protocol,the medical information is shared through the access control mechanism,the public information of the medical information is saved through the blockchain,and the real data of the medical treatment is encrypted and stored in the database or the cloud,which conveniently and effectively implements the storage of sensitive medical data and the sharing of information between systems.In the environment of the alliance chain,several network nodes are selected for security and performance testing.The experimental analysis shows that the proposed scheme has better performance in terms of security protection such as tamper resistance,privacy protection and throughput.In addition,the indexing mechanism proposed in this scheme can achieve fast retrieval and improve retrieval efficiency.By establishing a test network,the feasibility of this program in medical information storage is proved.The decentralized and non-tamperable management of the program using the blockchain can greatly improve the efficiency and the quality of medical services.It lays a good foundation for further research on the bottom technology of block chain and for exploring the application of block chain technology in the field of medical information.

Blockchain technology has the advantages of decentralization,trust removal,anonymity and non-tamperable.In order to more effectively ensure that users can safely identify and connect to the wireless network,this paper proposed a multi-stage cascade wireless security authentication scheme(MWSASB) based on blockchain technology.The MWSASB program designs a multi-stage cascade protocol process:registration phase,login and certification phase,and transaction phase.And it records the transaction of users’ information in the non-tamper and decentralized blockchain ledger by using workload proof and the extension of the longest chain.Firstly,during the registration phase,the user enters the registration information Then the cryptographic technology and the consensus mechanism are used to store the registration information on each node of the blockchain in the decentralized network.At the same time,during the login and authentication phase,the user inputs the login information,then login and authenticate with the blockchain server.After successful authentication the login information is also stored on each node of the blockchain.Secondly,in the transaction phase,the registration information and the login and authentication information are used to ensure that their information are securely recorded in the blockchain in the form of transactions.Finally,the security and computation of the MWSASB are analyzed.The results show that the MWSASB has security attributes such as wireless security authentication and can effectively avoid various common network attacks such as man-in-the-middle attacks,DDoS attacks,etc.In terms of computation,blockchain cannot be tampered with and cryptographic algorithm and consensus mechanism can be used for encryption verification,which can effectively reduce the number of calculations and improve the efficiency of security authentication.

With the rapid development of the Internet of things,environmental monitoring system has greatly improved the efficiency and transparency of government’s daily operation.However,most existing environmental monitoring systems currently provide services in a centralized manner and rely heavily on human control.Highly centralized system architectures are vulnerable to external attacks.In addition,it is relatively easy for criminals to destroy the authenticity of data,resulting in the public trust in environmental monitoring data is not high.To resolve these problems,this paper proposed an environmental monitoring data transmission scheme based on blockchain.The data acquired by the monitoring device is delivered to the data collection terminal by signature,and the data collection terminal verifies the data and writes it to the blockchain.Smart contracts analyze the data in real time and then issue the results.Then,PBFT consensus algorithm based on grouping was proposed to improve the scalability of the system.This paper analyzes the scheme and the results show that the environmental monitoring blockchain can ensure the security,authenticity and integrity of environmental monitoring data and verifies the feasibility of the scheme with specific cases.

The Vehicular Ad Hoc Network (VANET) is a kind of mobile ad hoc network (MANET) that supports vehicle to vehicle (V2V) and vehicle to infrastructure (V2I) communications,which is one of the core technology in Intelligent Transport System (ITS).Distributed data storage,point-to-point transmission,consensus mechanism and encryption algorithm of blockchain can warrant the security and reliability of VANET.However,the strong consistency and chain structure of blockchain can not match the two main characteristics of VANET,i.e.the rapid mobility of vehicle nodes and network instability.This research focus on the technical aspects of blockchain such as node,storage,cross-chain and consensus under the conditions of high mobility of vehicle nodes and volatility of network,and analyzes the existing problems and proposes solutions.We also prospect the future applications and research of blockchain in VANET which can be provided as a reference and basis.

The current implementation of blockchain systems generally suffer from performance and capacity deficiencies,making it impossible to achieve deeper popularity and wider application.Sharding is considered as the most likely technology to solve the blockchain bottleneck.However,at present,the mainstream sharding schemes generally suffer from the problem of sacrificing decentralization or security to improve performance.Based on the existing sharding technology,this paper proposed the jump Hash wight asynchronous consensus group scheme,which builds shards based on jump hash and dynamic weights,to improve the efficiency and rationality of shards creation.The algorithm satisfies the characteristics of high efficiency,fairness,and adaptability.The network fragmentation efficiency is improved by 8% compared with Ethereum.The workload of node migration is reduced by 25% compared with Ethereum.The asynchronous consensus group mechanism is introduced to improve the transaction security of sharding and effectively handle cross-shard transactions.Through theoretical analysis and experiments,the maximum transaction performance of blockchain dynamic sharding model based on jump Hash and asynchronous consensus group can reach 5000 transactions per second.

Block chain has the advantages of openness,non-tampering and distributed sharing of global accounts,but at the same time,these characteristics also bring about the privacy disclosure of transaction data,which seriously affects its application in many business areas,especially in the field of enterprise alliance chain.With the continuous development of block chain,how to protect the privacy of transaction data on block chain platform is a very worthwhile problem to study.To this end,firstly,the exi-sting methods of data privacy protection in block chain transactions were studied and their shortcomings were pointed out.Se-condly,the requirements of data privacy protection in block chain transactions were qualitatively analyzed.Each transaction data was divided into sensitive data and basic data.A demand analysis matrix was established to obtain the essential and implicit needs of transaction privacy protection and possible application scenarios.Then,combining the characteristics of symmetric encryption and asymmetric encryption and the consensus of intelligent contract,a privacy protection method of block chain transaction data based on double encryption was designed.The method mainly includes three modules:encrypting and storing transaction data by private data provider,using and decrypting private data to read transaction data,and sharing transaction data by private data accessible party.The workflow of each module was discussed in detail.Finally,the method was validated on the Mychain Platform,which combines with the actual business of multi-party participation in international trade.The evaluation results show that the proposed method can achieve fine-grained transaction data privacy protection at the field level,and can efficiently and steadily share private data on the chain and complete the full-link operation of private data.More than 1 million transaction tests have been completed on the block chain platform constructed by four nodes,and the TPS has reached 800.Compared with the original transaction performance without privacy protection,there is no significant reduction in performance.Compared with Bitcoin,Ethereum and other block chain platforms,the performance of the proposed method is improved dozens of times.

The Singularity and centrality of Medical Institutions’ existing database storage makes the security,integrity and traceability of electronic medical data impossible to be guaranteed,as a result,the medical privacy of patients is threatened.Although existing research has proposed a secure data storage scheme based on cloud storage,it needs to rely on a fully trusted third party to ensure the reliability of interaction.Therefore,this paper proposed a decentralized block chain information management scheme to achieve the safe storage of medical data.This scheme adopts improved PBFT consensus algorithm and optimized Hash encryption algorithm to store medical data safely and effectively in distributed database to ensure the integrity and traceabi-lity of medical data.At the same time,it proposes and designs a new data interaction system to prevent the direct interaction between the third party and the database,prevent the untrustworthy third party from maliciously destroying medical data and ensure the data.Finally,through access control and Lucene search mechanism to ensure patient privacy and achieve rapid retrieval of medical data.Experiments show that the improved PBFT consensus algorithm provides better stability and throughput than proof of work(POW) and delegated proof of stake (DPOS).Compared with the common database interaction,the data interaction system in this paper effectively prevents the direct operation of the database and has better security and tamper resistance.The experimental data show that the decentralized medical data storage system,the improved PBFT consensus algorithm and the data interaction system architecture have realized the security,traceability and tamper-proof of medical data,solved the difficulties of centralized storage,traceability and vulnerability of medical data,and laid a foundation for further promoting the application of block chain technology in the development of medical information industry.

In traditional medical information system,medical health data security storage and sharing have been becoming a challenging task.There are many restrictions in process of health data accessing and sharing for different people of identity,which spends a lot of resources and time on identity verification and data authentication.Aiming at these problems such as storage of the high concentration,unreliable data sharing security and the difficulty of reaching agreement,this paper proposed an alliance blockchain-based medical health data security model.According to the distribution of medical resources in reality,the medical institutions are ranked in the security model,and then combine DPOS with PBFT to ensure that the medical institutions can reach an agreement rapidly without a central node and share medical data in alliance.The security model has the advantages of decentralization,high security and tamper resistance,so it can store data records and other important information on the blockchain,but the original medical data is stored in Distributed database.The use’s medical health data is stored securely,meanwhile the sharing efficiency among the medical institutions is improved.Security analysis shows that the proposed model can protect medical health data within the scope of fault tolerance,prevent the data from tampering and the collusion problem.The proposed model has a 99% probability to ensure that the medical institutions can reach a consensus and share medical data in alliance by the consistency analysis.