Mobile users could offload some computations from the mobile devices to the nearby geo-distributed Fog servers which are provided by Fog computing infrastructure to release the computation workloads, and therefore improve quality of experience for themselves. However, mobile users may mistakenly offload their computations to the Fog servers which have been injected by some attackers, and these compromised Fog servers would possibly establish man-in-the-middle attack during the offloading procedure, and therefore induce privacy leaking and security issues. Meanwhile, as most of mobile users have natural mobility features, there still needs mobility-aware offloading technique for improving the offloading efficiency. Also, for Fog computing provider, to charge service fees for offloading service in a distributed fashion is necessary for providing geo-distributed offloading service. All of these challenges above motivate us to bring blockchain technique into Fog computing so as to verify authenticity of each Fog server. Hence, we propose a new Blockchain-based Mobility-aware Offloading (i.e., BMO) mechanism in this paper and we modeled the offloading problem in our proposed environment. Concretely, our BMO constantly maintains a set of candidate authorized Fog servers by leveraging blockchain, and the offloading decision could be made in a real-time fashion in mobile devices according to mobility prediction of users. Experimental results have demonstrated the feasibility and efficiency of BMO.

移动用户可以将一些计算从移动设备转移到附近的地理分布的Fog服务器，这些服务器由Fog计算基础结构提供，以释放计算工作量，从而提高自身的体验质量。但是，移动用户可能会错误地将其计算结果卸载到某些攻击者注入的Fog服务器上，而这些受损的Fog服务器可能会在卸载过程中建立中间人攻击，从而引发隐私泄漏和安全问题。同时，由于大多数移动用户具有自然的移动性，因此仍然需要感知移动性的卸载技术来提高卸载效率。另外，对于雾计算提供商，提供地理分布的卸载服务需要以分布式方式收取卸载服务的服务费。以上所有这些挑战促使我们将区块链技术引入Fog计算中，以验证每个Fog服务器的真实性。因此，我们提出了一个新的乙基于lockchain中号obility意识Ø在本文ffloading（即BMO）机制，我们模拟了我们所提出的环境卸载问题。具体而言，我们的BMO通过利用区块链不断维护一组候选授权的Fog服务器，并且可以根据用户的移动性预测在移动设备中实时做出卸载决策。实验结果证明了BMO的可行性和有效性。