Abstract: 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 . . .