Research On Modbus Protocol Analysis Based On DPI Technology

Because of its simple and easy-to-use features,the Modbus TCP protocol is widely used in industrial control systems such as petroleum,chemical,transportation,power and so on,and its security is related to all aspects of the country.Since the industrial control system adopts physical isolation design at the beginning of construction,it only focuses on the functional safety and physical safety of the industrial control system.The communication security is not considered in the initial design of the protocol.Modbus TCP protocol is lack of authentication,authorization and integrity verification,and it transmits data in plaintext in the process of communication.In the age of information and industrialization,its security is very vulnerable.In this paper,aiming at the problem of the Modbus TCP protocol itself and the security of the communication process,the protocol is improved.The protocols of protocol integrity verification,identity authentication and security enhancement are proposed.The method to control the access rights of Modbus TCP communication is studied on the basis of deep packet inspection.Based on digital signature technology,protocol identity authentication and integrity verification are implemented.The symmetric and asymmetric encryption and decryption technology is applied to realize the confidentiality requirement of the protocol.Based on the deep packet analysis,fine-grained access control policies are used to control the access permissions of the requestor.The improved protocol format in this paper can achieve the integrity verification,identity authentication and confidentiality requirements through the research and experimental analysis of the implementation method.And access control strategy can limit the access rights of the requestor.It has important significance and effect to improve the safety of Modbus TCP communication in the industrial control system.