The Internet of Things (IoT) has made fog computing a practical paradigm for running applications that are latency sensitive. The fog environment is populated by mobile devices that are both resource limited and not permanently installed. To ensure that time-sensitive Internet of Things applications can meet quality-of-service requirements in these types of environments, mobile users’ computing workloads can be offloaded to nearby fog servers. There are a lot of threats to the security and privacy of the fog servers as well. Users risk having their data compromised if they offload compute tasks to malevolent fog nodes. There are a lot of ways to keep fog settings from collapsing, but most of them depend on one solid center component, which could collapse at any moment. Blockchain technology has great potential as a decentralized method of data integrity maintenance. When it comes to secure offloading, the mobility of users has not been taken into account by the most recent blockchain offloading systems. Furthermore, it is critical to guarantee the quality of service limits of the IOT applications while taking user device mobility into account. Consequently, this investigation suggests a Blockchain-assisted Mobility-aware Secure Computation Outsourcing (MSCO) method for identifying the most appropriate approved fog servers for outsourcing tasks with reduced energy and computational expenses. The optimization problem is resolved through the implementation of a hybrid approach that combines Particle Swarm Optimization (PSO) and genetic algorithms. Based on the trial results, MSCO beat the previous approaches by an average of 11% when considering the whole cost, which includes latency and energy consumption.