The invention relates to a method for transferring data in a publish-subscribe system (100) comprising a key distribution server (200) and a plurality of communication devices (101, 102, 103, 104) which can be coupled to the key distribution server (200) and which comprise at least one server device and a number of client devices. The method comprises the following steps: a) providing (S101) a group key by means of the key distribution server (200) to a group (G) selected from the communication devices (101, 102, 103, 104) to establish group communications, secured by the group key, within the group (G) of selected communication devices (101, 102, 103, 104); b) providing (S102) a point-to-point connection which can be encrypted by means of a public key of an asymmetric encryption, between a first and a second communication device (101, 102) of the group (G); and c) transferring (S103) a message encrypted by means of the public key for the point-to-point connection and secured by means of the group key, between the first and the second communication device (101, 102).