Method for the tamper-proof storage of data in a first blockchain of a plurality of blockchains using a network system, wherein the network system comprises a plurality of subordinate subnetworks (102, 104), one of the blockchains of the plurality of blockchains being assigned to each subordinate subnetwork (102, 104) and each subordinate subnetwork (102, 104) comprising a plurality of data-processing units, the data-processing units forming nodes (110, 112, 114) of the corresponding subordinate subnetwork (102, 104), wherein the network system further comprises a superordinate subnetwork, a superordinate master blockchain being assigned to the superordinate subnetwork and comprising all the blocks of the plurality of blockchains, at least in the form of a hash value, and the superordinate subnetwork comprising at least one selected node (112, 114) from each subordinate subnetwork (102, 104) of the plurality of subordinate subnetworks (102, 104), wherein the method comprises: • creating a first additional block for the first blockchain which comprises the data to be stored as an entry, by means of a first node (110, 112) of a first subordinate subnetwork assigned to the first blockchain, • performing a first validity check of the first additional block by means of the first subordinate subnetwork, • in the event of a positive result of the first validity check, forwarding the first additional block to the superordinate subnetwork by means of the at least one selected node of the first subordinate subnetwork, which the superordinate subnetwork comprises, • performing a second validity check of the first additional block by means of the superordinate subnetwork, • in the event of a positive result of the second validity check, adding the first additional block to the master blockchain, • approval by means of the superordinate subnetwork for adding the first additional block to the first blockchain, • in the event of the approval, adding the first additional block to the first blockchain. wherein the network system comprises a plurality of subordinate subnetworks (102, 104), one of the blockchains of the plurality of blockchains being assigned to each subordinate subnetwork (102, 104) and each subordinate subnetwork (102, 104) comprising a plurality of data-processing units, the data-processing units forming nodes (110, 112, 114) of the corresponding subordinate subnetwork (102, 104), wherein the network system further comprises a superordinate subnetwork, a superordinate master blockchain being assigned to the superordinate subnetwork and comprising all the blocks of the plurality of blockchains, at least in the form of a hash value, and the superordinate subnetwork comprising at least one selected node (112, 114) from each subordinate subnetwork (102, 104) of the plurality of subordinate subnetworks (102, 104), wherein the method comprises: • creating a first additional block for the first blockchain which comprises the data to be stored as an entry, by means of a first node (110, 112) of a first subordinate subnetwork assigned to the first blockchain, • performing a first validity check of the first additional block by means of the first subordinate subnetwork, • in the event of a positive result of the first validity check, forwarding the first additional block to the superordinate subnetwork by means of the at least one selected node of the first subordinate subnetwork, which the superordinate subnetwork comprises, • performing a second validity check of the first additional block by means of the superordinate subnetwork, • in the event of a positive result of the second validity check, adding the first additional block to the master blockchain, • approval by means of the superordinate subnetwork for adding the first additional block to the first blockchain, • in the event of the approval, adding the first additional block to the first blockchain. • creating a first additional block for the first blockchain which comprises the data to be stored as an entry, by means of a first node (110, 112) of a first subordinate subnetwork assigned to the first blockchain, • performing a first validity check of the first additional block by means of the first subordinate subnetwork, • in the event of a positive result of the first validity check, forwarding the first additional block to the superordinate subnetwork by means of the at least one selected node of the first subordinate subnetwork, which the superordinate subnetwork comprises, • performing a second validity check of the first additional block by means of the superordinate subnetwork, • in the event of a positive result of the second validity check, adding the first additional block to the master blockchain, • approval by means of the superordinate subnetwork for adding the first additional block to the first blockchain, • in the event of the approval, adding the first additional block to the first blockchain.