The invention relates to a method for changing a group key GK for a secure data exchange in a group of network elements P1 . . . Pn (n=2, 3, . . . ) in a network system having a closed peer-to-peer configuration and a virtual synchronism supporting group communication protocol in a communication layer of a system architecture of the network system, wherein in the case of a change in a composition of the group of network elements P1 . . . Pn, caused by the join of a new network element Pn+1 into the group of network elements P1 . . . Pn or by the leave of a network element Pv (1≦v≦n) from the group of network elements P1 . . . Pn, a group key renewal, in which a network element Pi* (1≦i≦n) selected from the group of network elements P1 . . . Pn generates a new group key GKneu, is carried out and the new group key GKneu is transferred from the selected network element Pi to all the remaining network elements Pk (1≦k≦n, k≠i) of the group of network elements P1 . . . Pn in the changed composition, which the selected network element Pi* achieves by carrying out a key exchange with all the remaining network elements Pk in accordance with the Diffie-Hellman principle in order to transfer the new group key GKneu.