Authentication system for the authentication of a particular mobile electronic device from a plurality of mobile devices against a central server for the secure exchange of medical data between device and server, wherein the server is able to access a repository containing the medical data, comprising: - A central instantiating unit which is intended for instantiating the particular device, where in each case the instantiating unit installs an individualized device-specific application as an encryption unit on the particular device and wherein the application stores a key and a device ID in hidden form in a program memory of the device, wherein the instantiating unit stores an association between device ID and key in a central protected memory - An encryption unit which is installed locally on the device and is intended for generating a digital signature, wherein the signature is encrypted using the key stored by the instantiating unit and is generated from a signature prototype (SIG-UB), comprising at least the device ID and a time stamp, and wherein the encryption unit is furthermore intended for sending at least the signature and also the device ID to the server - A decryption unit which is installed on the central server and wherein the decryption unit comprises an access module to the central protected memory, wherein the decryption unit is intended for receiving the signature sent by the device with the device ID and for reading out the particular associated key for decryption from the device ID by accessing the central protected memory in order to decrypt the received signature using the key and from the signature prototype (SIG-UB) to read out the device ID as the decryption result, wherein the decryption unit is further intended for comparing the decryption result with the device ID for a match and when a match is found the decryption unit is further intended for executing an access to the repository using the device ID which has been read out. - A central instantiating unit which is intended for instantiating the particular device, where in each case the instantiating unit installs an individualized device-specific application as an encryption unit on the particular device and wherein the application stores a key and a device ID in hidden form in a program memory of the device, wherein the instantiating unit stores an association between device ID and key in a central protected memory - An encryption unit which is installed locally on the device and is intended for generating a digital signature, wherein the signature is encrypted using the key stored by the instantiating unit and is generated from a signature prototype (SIG-UB), comprising at least the device ID and a time stamp, and wherein the encryption unit is furthermore intended for sending at least the signature and also the device ID to the server - A decryption unit which is installed on the central server and wherein the decryption unit comprises an access module to the central protected memory, wherein the decryption unit is intended for receiving the signature sent by the device with the device ID and for reading out the particular associated key for decryption from the device ID by accessing the central protected memory in order to decrypt the received signature using the key and from the signature prototype (SIG-UB) to read out the device ID as the decryption result, wherein the decryption unit is further intended for comparing the decryption result with the device ID for a match and when a match is found the decryption unit is further intended for executing an access to the repository using the device ID which has been read out.