摘要:Were analyzed the deployment of a Smart Contract in a Public Organization in Ecuador, also were analyzed a current problem in the Ecuador´s Public Sector, like is the inefficient handling of resources. The objective of this research is to define a model Hyperledger based Blockchain solution. For this research the method selected to this analysis was the method deductive. As results we have a simplified model Hyperledger of the implementation of a Smart Contract, A mathematical model to prove the efficiency of the using Smart Contracts in the processes of hiring in the organizations publics and a Prototype of a generic algorithm for the deployment of a Smart Contract by means of based Blockchain solution. After the analysis it was concluded that the implementation of Smart Contracts both in the Ecuadorians sector public and in any other is a benefit to the organizations.

摘要:The blockchain is a radical innovation that has a considerable effect on payments, stock exchanges, cybersecurity, and computational law. However, its limitations in terms of the uncertainty involved in transaction confirmation are significant. In this paper, we describe the design of a decentralized voting protocol for the election of a block generator in a consortium blockchain and propose a new system framework that allows fast and exact confirmation of all transactions. In addition, to replace a transaction’s owner signature, a new interactive incontestable signature between the dealer and owner is used to confirm a transaction. By means of this signature, the dealer can assure the owner that a transaction will be permanently included in the blockchain in a non-repudiation manner. Moreover, the signatures of all transactions in a block share only one witness that provides membership proof between the block and these transactions. Finally, a security and performance analysis shows that the proposed schemes are provably secure and highly efficient.

摘要:智能合约被认为是第二代区块链的技术核心，它是区块链从虚拟货币、金融交易协议到 通用工具发展的必然结果。然而，目前智能合约技术尚不完善，对智能合约概念及内涵缺乏较 为系统的分析，对基于区块链的智能合约软件系统也缺少体系上的归纳与总结。有鉴于此，文 章从智能合约的基本定义入手，介绍了智能合约的发展历史、分类、规范等概念，进而从抽象 计算模型角度出发给出了智能合约的通用架构，并对智能合约语言与编译机制、合约部署机制 与合约运行过程予以详尽分析，上述结果将有利于把握智能合约未来研究方向。

摘要:Smart contract using Blockchain technology provides a mechanism to automatically exchange “cash” and “service” according to programmed conditions without requiring reliable third-party intervention. This results in reduction of time and cost for complex contract execution. Some contract execution require external information outside Blockchain as a trigger to execute the code specifying process for a certain contract. However, because Blockchain technology itself does not provide a function to directly access such external information, these applications require a proxy system called “oracle”. Oracle is in charge accessing external information, to verify it, and to write it on Blockchain. To avoid security incidents such as oracle writing malicious information on Blockchain, reliability of oracle must be required. This paper introduces a decentralized oracle equipping with verification and disputation mechanisms. To evaluate reliability of the proposed mechanisms, a simulation-based experiment was conducted. The experimental results showed that our solution could effectively suppress the interference of malicious participants and obtained reliable consensus results even if relatively many malicious participants joined in the consensus process on the proposed decentralized oracle.

摘要:Blockchain is an emerging technology that is increasingly supporting economic-ally-critical systems. The execution environment of blockchain is isolated from the external world and thus requires “blockchain oracles”: agents that fetch information from the external world. Blockchain is known to be highly reliable, but oracles are off-chain components that could be points of failure in whole blockchain-based systems. The reliability of blockchain oracles has yet to be investigated. In this paper, we propose a framework to compare and characterize existing blockchain oracles mechanisms from industry. Our approach for reliability modelling and architecture analysis of blockchain oracle systems uses Fault Tree Analysis. By calculating the reliability of oracles mechanisms, we can identify weak links that affect the overall reliability of a blockchain-based system.

摘要:Blockchain technology enables the operation of fully decentralized applications without the need for a central authority to manage the execution of the underlying process. However, a critical limitation in the technology today is the inability for such applications to query information external to the blockchain. Applications must make use of a decentralized oracle, i.e. a trusted source of external information. In this work we propose the paired-question decentralized oracle protocol, designed to extract true answers from the public. When querying the oracle, a user submits pairs of antithetic questions and voting users answer them for the chance to receive rewards. This new protocol lends itself to a simple formal analysis, and it is shown to strongly incentivize a Nash equilibrium of truthful reporting. This paper also discusses a number of extensions to the base protocol to improve its cost-effectiveness, security, and applicability.

摘要:Group data sharing enables information sharing between multiple parties for cooperative purposes. However, the existing schemes only consider scenarios in which all parties in the same organization want to share data. Achieving secure data sharing between users of different groups is also a relevant research issue. In this paper, we propose a blockchain-based data sharing scheme for multiple groups with anonymity and traceability. Owing to the consortium blockchain technique, any user in the system can easily verify the validity of the shared data without interacting with a third-party auditor. Additionally, the proposed scheme can not only enable data sharing between different groups with enhanced security anonymously but also achieve traceability and non-frameability.

摘要:Ethereum smart contract makes developers can deploy decentralized applications to inherit features from blockchain, such as decentralization and openness. Although Ethereum provided a decentralized platform, Ethereum Virtual Machine for smart contracts, it lacks of ability to fetch off-chain data. The general solution is Oracle data carrier. However, Oracle results in rising deployment costs. It requires Ethereum smart contract developers to follow format in programing contract, this constraint decreases the readability of smart contract. This paper proposes an off-chain data fetching architecture which is cost-effective and highly elastic for smart contract. It also compatible with exited contract, which makes Ethereum smart contract owner able to automate the reply process.

摘要:Smart contract, which could help developer deploy decentralized and secure blockchain application, is one of the most promising technologies for modern Internet of things (IoT) ecosystem today. However, Ethereum smart contract lacks of ability to communicate with outside IoT environment. To enable smart contracts to fetch off-chain data, this paper proposes a data carrier architecture that is cost-effective and elastic for blockchain-enabled IoT environment. Three components, namely Mission Manager, Task Publisher and Worker, are presented in the data carrier architecture to interact with contract developer, smart contract, Ethereum node and off-chain data sources. Selective solutions are also proposed for filtering smart contract event and decoding event log to fit different requirements. The evaluation results and discussions show the proposed system will decrease about 20USD deployment cost in average for every smart contract, and it is more efficient and elastic compared with Oraclize Oracle data carrier service.

摘要:Public key infrastructure (PKI) is the foundation and core of network security construction. Blockchain (Be) has many technical characteristics, such as decentralization, impossibility of being tampered with and forged, which makes it have incomparable advantages in ensuring information credibility, security, traceability and other aspects of traditional technology. In this paper, a method of constructing PKI certificate system based on permissioned BC is proposed. The problems of multiCA mutual trust, poor certificate configuration efficiency and single point failure in digital certificate system are solved by using the characteristics of BC distribution and non-tampering. At the same time, in order to solve the problem of identity privacy on BC, this paper proposes a privacy-aware PKI system based on permissioned BCs. This system is an anonymous digital certificate publishing scheme, which achieves the separation of user registration and authorization, and has the characteristics of anonymity and conditional traceability, so as to realize to protect user's identity privacy. The system meets the requirements of certificate security and anonymity, reduces the cost of CA construction, operation and maintenance in traditional PKI technology, and improves the efficiency of certificate application and configuration.

摘要:The public blockchain was originally conceived to process monetary transactions in a peer-to-peer network while preventing double-spending. It has since been extended to numerous other applications including execution of programs that exist on the blockchain called “smart contracts.” Smart contracts have a major limitation, namely they only operate on data that is on the blockchain. Trusted entities called oracles attest to external data in order to bring it onto the blockchain but they do so without the robust security guarantees that blockchains generally provide. This has the potential to turn oracles into centralized points-of-failure. To address this concern, this paper introduces ASTRAEA, a decentralized oracle based on a voting game that decides the truth or falsity of propositions. Players fall into two roles: voters and certifiers. Voters play a low-risk/low-reward role that is resistant to adversarial manipulation while certifiers play a high-risk/high-reward role so they are required to play with a high degree of accuracy. This paper also presents a formal analysis of the parameters behind the system to measure the probability of an adversary with bounded funds being able to successfully manipulate the oracle’s decision, that shows that the same parameters can be set to make manipulation arbitrarily difficult—a desirable feature for the system. Further, this analysis demonstrates that under those conditions a Nash equilibrium exists where all rational players are forced to behave honestly

摘要:Fog computing is a new computing paradigm that can provide flexible resources and services at the edge of network. It is an extension of cloud computing and usually cooperated with cloud computing. Therefore, end users, fog nodes, and cloud servers can form a three-layer service model in practical application. In this model, they should have an agreement on a service contract,which contains every party's rights and obligations before the beginning of the service.However, due to lack of trust, it will suffer from some fairness problems during signing a service contract.Contract signing protocol allows two or more mutual distrust entities to sign a predefined digital contract in a fair and effective way. In this paper, we propose a fair three-party contract signing protocol based on the primitive of blockchain, which can be applied to the scenario of fog computing. Our proposed construction allows the participants to sign a contract in a fairway without the involvementof an arbitrator.Moreover, the privacy of the contract content can be preserved on the public chain. Finally, we realize the proposed protocol through the private blockchain and provide the experimental simulation that analyzes the efficiency and effectiveness.

摘要:In blockchain ecosystems, an Oracle is a service tool which provides real-world data for smart contracts and other blockchain applications. At present, there are several Oracle implementation schemes, e.g. centralized Oracles, decentralized Oracles, and hardware Oracles. However, these schemes typically suffer from single source of data and low scalability. Application Specific Knowledge Engine (ASKE) is an integrated topic/application-centered knowledge portal that supports effective information retrieval and analysis. Inspired by ASKE, in this paper, we propose a novel Oracle implementation scheme. The proposed scheme can realize multi-source data extraction and analysis, then working prototypes are demonstrated to show the validity of the scheme.

摘要:Smartphones have become an indispensable item for people and are carried with people throughout the day. They are often embedded with various sensors such as accelerometers, magnetometers, barometers, microphone, humidity, light sensors, cameras, along with GPS.

摘要:Thanks to its decentralized structure and immutability, blockchain technology has the potential to address relevant security and privacy challenges in the Internet of Things (IoT). In particular, by hosting and executing smart contracts, blockchain allows secure, flexible, and traceable message communication between IoT devices. The unique characteristics of IoT systems, such as heterogeneity and pervasiveness, however, pose challenges in designing smart contracts for such systems. In this paper, we study these challenges and propose a design approach for smart contracts used in IoT systems. The main goal of our design model is to enhance the development of IoT smart contracts based on the inherent pervasive attributes of IoT systems. In particular, the design model allows the smart contracts to encapsulate functionalities such as contractlevel communication between IoT devices, access to data-sources within contracts, and interoperability of heterogeneous IoT smart contracts. The essence of our approach is structuring the design of IoT smart contracts as self-contained software services, inspired by the microservice architecture model. The flexibility, scalability and modularity of this model make it an efficient approach for developing pervasive IoT smart contracts.