I. Introduction
Cyber-Physical systems (CPSs) refer to the systems closely integrated with physical processes and cyber components. With full range of capabilities such as control, computation, and communication, CPSs are gradually applied to various critical infrastructures including robotics systems, smart grid, and environment monitoring [1]. However, with the data transmitted in the unprotected wireless network, the vulnerability of CPSs brings new risks of the potential safety hazards, which may cause great damage such as economical loss, facility damages, and even enormous loss of human lives. Therefore, the research of security issues is an essential demand to guarantee the normal operation in CPSs, so that it has attracted considerable interest during the recent years [2].