With the development of 5G(5th generation mobile networks) technology, smart cities are an inevitable trend in modern city development. Among them, smart city services are the foundation of 5G-enabled smart cities. As an emerging and informational city service model, crowdsourcing has been widely used in our daily life. However, in the existing crowdsourcing systems, the requesters and the workers are usually required to use the crowdsourcing platform as the trust center, and the payment depends on the third-party central payment institutions, which have a massive security risk. Once these centers are attacked or do evil, it will bring higher losses to the crowdsourcing parties. These problems will negatively affect the further development of 5G-enabled smart cities. To address these issues, we propose a blockchain-empowered and decentralized trusted service mechanism for the crowdsourcing system in 5G-enabled smart cities. In the proposed mechanism, the crowdsourcing service process is divided into nine stages: initialization, task submission, task publication, task reception, scheme submission, scheme arbitration, payment, task rollback, and service compensation. The smart contract controls the execution of each step in each stage, and the payment is completed by blockchain without the involvement of third-party central institutions. Finally, we develop smart contracts to conduct experiments based on Ethereum and compare it with the existing crowdsourcing system. The experimental results show the effectiveness and applicability of the crowdsourcing system service mechanism without the central institutions.

随着5G（第五代移动网络）技术的发展，智慧城市已成为现代城市发展的必然趋势。其中，智慧城市服务是启用5G的智慧城市的基础。作为一种新兴的信息化城市服务模式，众包已广泛应用于我们的日常生活中。但是，在现有的众包系统中，通常要求请求者和工作人员使用众包平台作为信任中心，并且支付依赖于第三方中央支付机构，该第三方中央支付机构具有巨大的安全风险。这些中心一旦受到攻击或行恶，就会给众包方带来更大的损失。这些问题将对支持5G的智慧城市的进一步发展产生负面影响。为了解决这些问题，我们为启用5G的智慧城市中的众包系统提出了一种基于区块链的，去中心化的可信服务机制。在提出的机制中，众包服务过程分为九个阶段：初始化，任务提交，任务发布，任务接收，方案提交，方案仲裁，付款，任务回滚和服务补偿。智能合约控制每个阶段中每个步骤的执行，并且支付由区块链完成，而无需第三方中央机构的参与。最后，我们开发智能合约以基于以太坊进行实验，并将其与现有众包系统进行比较。实验结果表明，没有中央机构的众包系统服务机制的有效性和适用性。