The security of communication protocols in the smart grid system is a crucial concern. An adversary can exploit the lack of confidentiality and authentication mechanism to cause damaging consequences. In the substation automation systems that rely on multicast communication between various intelligent electronic devices, the lack of security features in the standard IEC61850 and IEC62351 can invite attackers to manipulate the integrity of the employed publisher–subscriber communication paradigm to their advantage. Consequently, many researchers have introduced various approaches offering authenticity and confidentiality. However, such schemes and methods for the aforesaid standards have computational limitations in compliance with the stringent timing requirements of specific applications in the smart grid. In this paper, we propose an approach that can fully secure the publisher–subscriber communication against confidentiality attacks. In this direction, we develop a demo tool to validate the performance of our proposed security approach for potential factors such as timing requirements and the size of the messages. Finally, we evaluate our scheme considering the requirements of the GOOSE, SMV, and MMS protocols in the substation automation systems.