For end-to-end securing of transactions between a mobile terminal and an Internet server on the application layer, cryptographic transaction identification records, which are directed by the Internet server application to transaction partner applications in the mobile terminal, are stored, assigned to the mobile terminal, in a proxy server. In each case a record identification is transmitted to the mobile terminal for a stored transaction identification record as well as a proxy record, which is calculated by the proxy server from the respective stored transaction identification record. In each case a record identification and a proxy record are taken by the proxy server from the messages directed by the mobile terminal to the Internet server application. The correspondence of the taken proxy record with the proxy record is checked, which is calculable from the stored transaction identification record determined through the taken record identification, and, in the case of agreement, the stored transaction identification record determined through the taken record identification is transmitted to the Internet server application.