Evaluation of secure signal transmission in automatic control using SSH tunneling

Nowadays, the need to communicate remote devices is one of common task for control systems. High popularity and availability of Internet and intranets enables easy designing of distributed control systems which has to fulfill signal transmission security requirements in order to protect transmitted data from unprivileged access or change. There are several approaches to transmission security problem. This paper focuses on low cost solution - TCP connections tunneling using well known SSH protocol. In opposition to commercial solutions, the use of SSH client application requires almost no user privileges on client system. To accomplish this task LVST-universal tool for TCP/IP data tunneling has been built. The tool is used for securing measurement/control data transmission, SCADA system connection as well as secure operation on remote PLCs and data acquisition servers. Application of created tool for laboratory scale heat distribution plant is presented.