The present invention relates to a process and a system for selectable data transmission. Authentication data and an electronic key are generated, whereby the electronic key is stored as assigned to the authentication data. Data are encrypted into encrypted data by means of an encryption module of a central module and by means of at least part of the electronic key. A signaling message is transmitted to a first communications terminal. A second communications terminal is selected by means of the first communications terminal. On the identification of the selected second communications terminal, the encrypted data are transmitted to the second communications terminal. At least part of the electronic key is transmitted to the second communications terminal by means of an authentication module of the central module. The encrypted data are decrypted by means of a decryption module of the second communications terminal and by means of at least the part of the electronic key.