The present invention relates to a computer-implemented method for replacing a data string by a placeholder in a replacement device and, when necessary, for reconstituting the data string from the placeholder in the replacement device. There is a need for a central system for replacing a data string by a placeholder for a whole company which enables all applications to be protected and, when necessary, to have controlled access to sensitive data strings. It is necessary to make possible a central administration but at the same time to offer application-related access points throughout the company without long network communication paths. It is therefore proposed according to the invention that the replacement device comprises a plurality of nodes of a distributed system carrying out the replacement, a management device connected to the nodes stores all the configuration data of the nodes necessary for the initialization of the nodes, at least one node is initialized centrally with the configuration data provided by the management device and the nodes do not permanently store the configuration data so that all the configuration data previously present on the node are deleted in the case of a shutdown or a failure of a node, wherein the method for replacing the data string by the placeholder has the steps: reception of the data string from an application, selection of at least one node carrying out the replacement from the plurality of nodes of the distributed system, onward transmission of the data string to the at least one selected node, generation of a placeholder replacing the data string in the at least one selected node and passing the placeholder to the application.