The recent advancements of digital substations and their integration within modern smart grids have made the security and privacy of communication among the entities a critical requirement. This is especially relevant to access control and authentication processes in substation automation systems. This paper proposes an attribute-based access signature scheme for secure communication in substations’ architecture. The proposed scheme provides fine-grained access control, ensuring only authorized entities can sign messages under hybrid attribute-based policies. By employing a certificateless primitive, the system allows efficient signature generation and verification with a semi-trusted third party. Also, key security properties, including unforgeability against chosen-message and collusion attacks, are formally defined and proven, ensuring the scheme’s robustness against unauthorized access. The evaluation and discussion show that the scheme supports the delegation of signing authority and enables efficient signatures when required. The proposed construction demonstrates computational efficiency and compatibility with energy systems environments, serving as a secure role/rule-based access control scheme.