Nowadays, smart applications are increasing day by day to improve the standard of living in smart cities. A modern-day smart city is characterized by the presence of numerous smart Information and Communication Technology (ICT)-enabled services such as automated healthcare, automatic building monitoring, home automation, smart parking, traffic management, data security, among others. Such cities employ multitudes of Internet of Things (IoT) devices to collect and share data between trusted users by means of a centralized intermediary for monitoring and control of the myriad automatic activities. However, a centralized intermediary is plagued by issues such as single point of failure, risk of data loss, man-in-the-middle attack, and so forth. Blockchain-based smart contracts for automated control in smart cities provide a decentralized and secure alternative. In this paper, an Ethereum based system design for decentralized applications in smart cities has been proposed that enables systems to share data without an intermediary between trusted and non-trusted stakeholders using Ethereum based self-executing contracts. Such contracts allow automated multi-step workflows for smart applications. Two use cases, have been considered namely smart healthcare and smart building monitoring, as proof of stake of the proposed Ethereum based contract. The performance of the proposed scheme for these use cases has been presented with Keccack 256 transaction hash, the total number of transactions, gas consumed by each contract. Such an attempt is a worthwhile addition to state of the art as evident from the results presented herein. The modeling simulation and analysis of hashing power shows that for hashing power greater than 55% the probability of double spending attack reaches to 42% maximum. So it is concluded that the probability of double spending increases with the increase of transaction values.

中文翻译：

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基于区块链的智慧城市中自动控制系统的智能合约

如今，智能应用程序正日益增加，以提高智能城市的生活水平。现代化的智慧城市的特点是拥有众多基于智能信息和通信技术（ICT）的服务，例如自动化医疗保健，自动楼宇监控，家庭自动化，智能停车，交通管理，数据安全等。这样的城市使用大量的物联网（IoT）设备，通过集中的中介机构来监视和控制无数的自动活动，从而在受信任的用户之间收集和共享数据。但是，集中式中介会遇到诸如单点故障，数据丢失的风险，中间人攻击等问题。用于智能城市中自动控制的基于区块链的智能合约提供了去中心化和安全的替代方案。在本文中，已经提出了针对智能城市中的分散应用程序的基于以太坊的系统设计，该系统设计使系统能够使用基于以太坊的自动执行合同在无需信任和不信任的利益相关者之间进行中介的情况下共享数据。这样的合同允许针对智能应用程序的自动化多步骤工作流。已经考虑了两个用例，即智能医疗保健和智能建筑监控，作为拟议的基于以太坊的合同的股权证明。针对这些用例的拟议方案的性能已通过Keccack 256交易哈希，交易总数，每个合同消耗的天然气进行了介绍。从本文呈现的结果可以明显看出，这种尝试是对现有技术的一种有价值的补充。对散列能力的建模仿真和分析表明，对于散列能力大于55％的情况，双花攻击的可能性最大达到42％。因此可以得出结论，双倍消费的可能性随着交易价值的增加而增加。