A method of controlling access to an electronically controllable device, wherein the electronically controllable device is a vehicle, comprising the steps of: Establishing a communication link between a mobile communication device and a central control platform via a communication network, Creating a booking for an electronically controllable device in the central control platform and transmitting first data for the booking from the central control platform to the mobile communication device, the data being in the form of access information for access to the electronically controllable device and for processing in the mobile communication device, whereby additionally, second data is transmitted from the central control platform to the mobile communication device in a data container, wherein the second data contains booking information, wherein the second data is signed in the central platform prior to transmission and encrypted with an individual key, wherein the individual key is assigned to an access control unit in the electronically controllable device, and wherein the encrypted second data is stored in the mobile communication device, whereby access to the content of the data container in the mobile communication device is not possible at any time, or at least this content cannot be changed without destroying the signature, the mobile communication device for accessing the electronically controllable device is wirelessly coupled to the access control unit of the electronically controllable device, wherein at least the second data and at least a subset of the first data are transmitted to the access control unit, the access control unit decrypts the second data and checks a signature of the second data and, if the check is successful, a configuration of the access control unit is adapted as a function of the decrypted data, the booking information being read out and stored in the system after the signature of the second data has been successfully checked, whereupon an opening authorization of the user can then be verified and with the updated booking information the booking is verified on the basis of the first data and the user is granted access to the electronically controllable device, whereby in operation initially a direct data transmission from the central control platform to the access control unit takes place and in the event of failure alternatively the transmission takes place via the encrypted transport on the mobile communication device. Establishing a communication link between a mobile communication device and a central control platform via a communication network, Creating a booking for an electronically controllable device in the central control platform and transmitting first data for the booking from the central control platform to the mobile communication device, the data being in the form of access information for access to the electronically controllable device and for processing in the mobile communication device, whereby additionally, second data is transmitted from the central control platform to the mobile communication device in a data container, wherein the second data contains booking information, wherein the second data is signed in the central platform prior to transmission and encrypted with an individual key, wherein the individual key is assigned to an access control unit in the electronically controllable device, and wherein the encrypted second data is stored in the mobile communication device, whereby access to the content of the data container in the mobile communication device is not possible at any time, or at least this content cannot be changed without destroying the signature, the mobile communication device for accessing the electronically controllable device is wirelessly coupled to the access control unit of the electronically controllable device, wherein at least the second data and at least a subset of the first data are transmitted to the access control unit, the access control unit decrypts the second data and checks a signature of the second data and, if the check is successful, a configuration of the access control unit is adapted as a function of the decrypted data, the booking information being read out and stored in the system after the signature of the second data has been successfully checked, whereupon an opening authorization of the user can then be verified and with the updated booking information the booking is verified on the basis of the first data and the user is granted access to the electronically controllable device, whereby in operation initially a direct data transmission from the central control platform to the access control unit takes place and in the event of failure alternatively the transmission takes place via the encrypted transport on the mobile communication device.