A communication method is provided for transmitting useful data between a first traffic participant, at least one second traffic participant, and a central communication device. It is provided that the first traffic participant provides a data packet and transmits it to the central communication device, the data packet being assigned to a changing key that is transmitted together with the data packet, and that the first traffic participant transmits an identifier together with the key to the second traffic participant, and that the second traffic participant requests from the central communication device, using the key, the data packet assigned thereto, and assigns it to the first traffic participant. Also provided is a communication system.