The boom for robotics technologies in recent years has also empowered a new generation of robotics software. The Robot Operating System (ROS) is one of the most popular frameworks for robotics researchers and makers which is moving towards commercial and industrial use. Security-wise however, ROS is vulnerable to attacks. It is rather easy to inject or eavesdrop data in a ROS application. This opens many different ways to attack a ROS application resulting in data loss, monetary damage or even physical injury. In this paper we present a secure communication channel enabling ROS-nodes to communicate with authenticity and confidentiality. We secure ROS on a peer-to-peer basis in the direct interaction between publishers and subscribers. We describe the implementation changes we have made to the ROS core and assess the overhead introduced by the new security functions.