  This paper investigates computation offloading in blockchain-empowered
Internet of Things (IoT), where the task data uploading link from sensors to a
base station (BS) is protected by intelligent reflecting surface (IRS)-assisted
physical layer security (PLS). After receiving task data, the BS allocates
computational resources provided by mobile edge computing (MEC) servers to help
sensors perform tasks. Existing blockchain-based computation offloading schemes
usually focus on network performance improvements, such as energy consumption
minimization or latency minimization, and neglect the Gas fee for computation
offloading, resulting in the dissatisfaction of high Gas providers. Also, the
secrecy rate during the data uploading process can not be measured by a steady
value because of the time-varying characteristics of IRS-based wireless
channels, thereby computational resources allocation with a secrecy rate
measured before data uploading is inappropriate. In this paper, we design a
Gas-oriented computation offloading scheme that guarantees a low degree of
dissatisfaction of sensors, while reducing energy consumption. Also, we deduce
the ergodic secrecy rate of IRS-assisted PLS transmission that can represent
the global secrecy performance to allocate computational resources. The
simulations show that the proposed scheme has lower energy consumption compared
to existing schemes, and ensures that the node paying higher Gas gets stronger
computational resources.
