Information technologies play a crucial role in the development, operation, and technical service of critically important infrastructures that have high requirements for reliability and safety. Bugs (faults) or alarms in high operation risk, relating to critically important infrastructures, may lead to destroying or severe damages of expensive cost equipment, considerably harm the environment. Design of nuclear power plants (NPP) safety important systems are based on meeting requirements of regulatory documents and quality assurance of soft- and hardware complexes within the whole life-cycle. An essential problem of the soft- and hardware complexes quality assurance is the procedure of forming requirements to a developed or modified system and their subsequent verification. Increasing the NPP safety important systems requirements at all stages of the life-cycle is concerned with increasing the complexity and functionality if the software and has led to the necessity of developing approaches for the justification of both the safety of the system themselves and the software involved in their make-up. The paper considers an approach based on constructing the “safety functions,” meeting which is verified in the sequel. This approach is applied under the top-level APCS (automated process control systems) hardware verification and can be applied for the analysis of fault tolerance, information, and cyber safety of soft- and hardware complexes.