A method of protecting signaling messages in a hop-by-hop network communication link between a source node (PLMN-A,HSS,MME,SGSN,PCRF) in the network and a destination node (PLMN-B,HSS,MME,SGSN,PCRF) in the network, the communication link including at least one intermediate node (IPX-A, IPX-B) in the network between the source node and the destination node, the method comprising: - providing the source node with a source node public digital signature verification key and a respective source node private digital signature key associated with said public digital signature verification key; - providing the destination node with said source node public digital signature verification key associated with the source node private digital signature key; - at the source node: - building a signaling message including a sequence of Information Elements; - for each Information Element, calculating an Information Element hash value of the Information Element; - calculating a sequence hash value of a concatenation of the calculated Information Element hash values; - generating a source node digital signature by digitally signing the calculated sequence hash value, said digitally signing comprising exploiting the source node private digital signature key and the source node public digital signature verification key; - including the source node digital signature in the signaling message, and - sending the signaling message; - at the intermediate node: - receiving the signaling message and forwarding it to the destination node directly or via a next intermediate node; - at the destination node: - receiving the signaling message. - providing the source node with a source node public digital signature verification key and a respective source node private digital signature key associated with said public digital signature verification key; - providing the destination node with said source node public digital signature verification key associated with the source node private digital signature key; - at the source node: - building a signaling message including a sequence of Information Elements; - for each Information Element, calculating an Information Element hash value of the Information Element; - calculating a sequence hash value of a concatenation of the calculated Information Element hash values; - generating a source node digital signature by digitally signing the calculated sequence hash value, said digitally signing comprising exploiting the source node private digital signature key and the source node public digital signature verification key; - including the source node digital signature in the signaling message, and - sending the signaling message; - building a signaling message including a sequence of Information Elements; - for each Information Element, calculating an Information Element hash value of the Information Element; - calculating a sequence hash value of a concatenation of the calculated Information Element hash values; - generating a source node digital signature by digitally signing the calculated sequence hash value, said digitally signing comprising exploiting the source node private digital signature key and the source node public digital signature verification key; - including the source node digital signature in the signaling message, and - sending the signaling message; - at the intermediate node: - receiving the signaling message and forwarding it to the destination node directly or via a next intermediate node; - receiving the signaling message and forwarding it to the destination node directly or via a next intermediate node; - at the destination node: - receiving the signaling message. - receiving the signaling message. <EOS>