This paper presents a public key infrastructure for open multi-agent systems of embedded agents. Open multi-agent systems of embedded agents are a set of network embedded systems cooperating in real time to achieve their goal without a central server issuing commands. In this context, agents are very prone to attacks as they can be confronted with new agents with unknown goals and as they often rely on wireless ad hoc communications. The key infrastructure we propose allows the agents to communicate without the risk of their messages being tampered with. Thus, providing foundations for more advanced security solutions such as trust management systems. In order to do that, we leverage the agent’s capabilities to establish and maintain the infrastructure by pro- viding self-organization and trust management rules. Once established, the infrastructure provides a way for the agents to assert their right to take part in the system operations with certificates and to secure their communications with asymmetric cryptography. As a result, agents can communicate securely without the risk of their identities being stolen and their communications being tampered with. They are also being able to exclude intruders. The work proposed in this paper paves the way to build more secure open decentralized systems of autonomous embedded systems. To make our solution general and adaptable to many situations, we decoupled the cryptographic and trust management details from the infrastructure itself.