Smart grid technology drives economic and social development but raises vulnerability to cyber threats due to digital substations’ growing reliance. To counter these risks, recent updates to communication standards, including encryption and authentication processes, have been integrated into the infrastructure. Notably, adhering to the IEC 62351 standard governing the GOOSE protocol for substation communication faces practical challenges due to conflicting time requirements with traditional security procedures. In this paper, we present an innovative geometric approach for GOOSE message authentication and encryption. Utilizing vector coordinate shifts, our method exhibits efficiency and speed of implementation, ensuring compliance with the protocol’s stringent time constraints. Importantly, unlike other approaches in the literature, our technique has the potential to be easily applicable and effective for a wide range of infrastructures without requiring the use or addition of specific hardware components or changes to the GOOSE message format, while guaranteeing high performances and computational simplicity. The paper is complemented by a simulation campaign on a digital substation model, assessing the approach’s performance and its efficacy in countering cyber threats.