Research and Implementation of Modbus TCP Security Enhancement Protocol

Abstract Considering the security problem of Modbus TCP protocol, such as the lack of authentication mechanism, the protection mechanism of data transmission and abuse of function code, a secure industrial control communication protocol(Modbus-S protocol) is designed based on the original Modbus TCP protocol, which uses symmetric key algorithm to ensure the confidentiality of data; the uniqueness of data is guaranteed by the synchronization mechanism based on hash algorithm; digital signature algorithm is used to ensure the verifiability and integrity of data; finally, “White List” filtering mechanism is used to manage function codes based on roles to effectively prevent abuse of function codes. Through the verification and analysis of experiment, Modbus-S can fully compensate for the design defects of Modbus TCP protocol. Compared with the existing methods, this method has higher security and can comprehensively improve the communication security of Modbus TCP protocol.