Communication security problem and solution in safety-related system

Security in control system is an important issue. To safety-related system it is more critical. A safety-security communication measure to counteract nature or intend data modification is proposed, which based on refining characters of data with MD5 approach. And to some low speed network a 2-refine approach is introduced which based on MD5 and CRC. A confidential communication to secure all the data is proposed, too. Furthermore, the key distribution approaches named KDC and DKD are introduced.