A method of verifying secret keys in a system comprising an initiator node and a distributed network, wherein the distributed network comprises a plurality of nodes (100.1 to 100.6) connected to a shared medium of the distributed network, wherein each node of the plurality of nodes is member of at least one group of a plurality of groups (LG 1 - LG 4), wherein each group is associated with a secret group key (K LID 1 - K LID 5), wherein each node of the plurality of nodes is provided with only the one or more secret group keys (K LID 1-K LID 5), of which it is member, said method comprising: the initiator node, broadcasting a verification request on the shared medium to be received by the plurality of nodes (100.1 to 100.6); each of the plurality of nodes (100.1 to 100.6), receiving the verification request broadcast on the shared medium by the initiator node; each of the plurality of nodes (100.1 to 100.6), generating a code sequence on the basis of each secret group key (K LID 1 - K LID 5) associated with a respective one of the one or more logical groups, of which the receiving node is member, from a predefined data sequence; each of the plurality of nodes (100.1 to 100.6), generating a verification response comprising one code sequence for each of the one or more logical groups, of which the receiving node is member, each of the plurality of nodes (100.1 to 100.6), broadcasting the verification response on the shared medium to be received by the initiator node, the initiator node, receiving verification responses broadcast from the plurality of nodes (100.1 to 100.6) on the shared medium, the initiator node, collecting the code sequences comprised in the received verification responses; and the initiator node, confirming integrity of the plurality of nodes (100.1 to 100.6) by comparing the code sequences, wherein each secret group key is known only to those nodes which are members of the respective logical group and is unknown to the initiator node, each code sequence of the verification response is generated by a keyed hash function or a message authentication code algorithm using the respective secret group key (K LID 1 - K LID 5) and applied on the predefined data sequence. the initiator node, broadcasting a verification request on the shared medium to be received by the plurality of nodes (100.1 to 100.6); each of the plurality of nodes (100.1 to 100.6), receiving the verification request broadcast on the shared medium by the initiator node; each of the plurality of nodes (100.1 to 100.6), generating a code sequence on the basis of each secret group key (K LID 1 - K LID 5) associated with a respective one of the one or more logical groups, of which the receiving node is member, from a predefined data sequence; each of the plurality of nodes (100.1 to 100.6), generating a verification response comprising one code sequence for each of the one or more logical groups, of which the receiving node is member, each of the plurality of nodes (100.1 to 100.6), broadcasting the verification response on the shared medium to be received by the initiator node, the initiator node, receiving verification responses broadcast from the plurality of nodes (100.1 to 100.6) on the shared medium, the initiator node, collecting the code sequences comprised in the received verification responses; and the initiator node, confirming integrity of the plurality of nodes (100.1 to 100.6) by comparing the code sequences, wherein each secret group key is known only to those nodes which are members of the respective logical group and is unknown to the initiator node, each code sequence of the verification response is generated by a keyed hash function or a message authentication code algorithm using the respective secret group key (K LID 1 - K LID 5) and applied on the predefined data sequence.