The exponential growth of connected autonomous embedded devices (aka the IoT) will pose huge challenges with regard to device-and inter-device communication security. Features like encrypted communication, device authentication and device authorisation must be appropriately addressed in order to provide a reliable and penetration-resistant device network. However, recent examples of cyber-attacks on such networks and the current lack of generic standards have shown that there is still a long way to go.Public key infrastructures (PKI) and digital certificates are key elements of today's secure Internet infrastructure. This paper analyses the benefits, limitations and suitability of both concepts for IoT deployments in combination with secure communication protocols. Based on this assessment it proposes an adopted PKI architecture that provides and manages customised X.509 digital certificates.