The Smart Grid is a complex architecture that involves several networks (Home Area Network, Neighbor Area Network, Wide Area Network, etc.) to exchange data between Intelligent Electronic Devices (IEDs) at Home and the Control Center at the energy supplier side. This communication can be vulnerable to significant attacks (Eavesdropping, spoofing, replay attacks, DoS). Hence, security is essential to protect the exchange of sensitive data necessary to the good operation of the electrical grid. In this paper, we propose a security architecture, based on Blockchain technology, to avoid most attacks. Simulation experiments show that latency can be in or out the limits set for Smart Grid applications.