The electric power grid has been developed over last century and it is facing many problems. The electric grid lacks the ability to adapt and integrate intermittent energy sources and active customer participation. Numbers of architecture have been proposed by various agencies for smart grid. Micro-grid is the lowest node in the hierarchy of smart grid that has to be developed efficiently for optimal performance. Smart grid, which will involve multidirectional energy and information flows, may be susceptible to cyber attack due to involvement of ICT in managing the smart grid. Multiagent based public key infrastructure (PKI) is proposed for the authentication of participating devises in micro-grid. The agents utilize information exchanges from neighboring agents to construct knowledge base that can be used in making efficient decision support system. The studies suggest that multi-agent perform better under the given circumstance and pressure providing the real-time communication.