Method for verifying the ownership of a vehicle by an authentication server comprising a time counter, the vehicle comprising a time counter, locking/closing means comprising a wireless communication module that can communicate with a portable communication device, such as a portable telephone, the vehicle is associated with a physical ignition key, the portable communication device can communicate with the authentication server, characterised in that the method comprises the following steps: - Synchronisation (110, 111) of the time counter of the vehicle with the time counter of the authentication server, - Authentication (100, 101, 102) of the owner of the vehicle on the authentication server via the owner's portable communication device, such as a mobile phone, to create on the server at least one ownership link between the owner and the vehicle, and transmission of a registration request from the vehicle to the authentication server via its portable communication device, the registration request comprising information on the identity of the owner, and identification of the vehicle, - reception by the authentication server, following a request for activation (204, 205) of the locking/closing means by the owner of the vehicle, of a state of simultaneous presence in the vehicle of the physical starting key and of the owner of the vehicle to the authentication server via the owner's portable communication device, in order to validate the at least one link created, the state of presence comprising the date of the vehicle's time counter, - transmission from the authentication server of a signal validating the use of the locking/closing means to the owner's portable communication device, if the state of presence of the owner and of the physical key of the vehicle are confirmed and if the date of the time counter of the vehicle transmitted corresponds with the time counter of the authentication server, and subsequently enables the vehicle to be started via the owner's portable communication device without the physical start key. - Synchronisation (110, 111) of the time counter of the vehicle with the time counter of the authentication server, - Authentication (100, 101, 102) of the owner of the vehicle on the authentication server via the owner's portable communication device, such as a mobile phone, to create on the server at least one ownership link between the owner and the vehicle, and transmission of a registration request from the vehicle to the authentication server via its portable communication device, the registration request comprising information on the identity of the owner, and identification of the vehicle, - reception by the authentication server, following a request for activation (204, 205) of the locking/closing means by the owner of the vehicle, of a state of simultaneous presence in the vehicle of the physical starting key and of the owner of the vehicle to the authentication server via the owner's portable communication device, in order to validate the at least one link created, the state of presence comprising the date of the vehicle's time counter, - transmission from the authentication server of a signal validating the use of the locking/closing means to the owner's portable communication device, if the state of presence of the owner and of the physical key of the vehicle are confirmed and if the date of the time counter of the vehicle transmitted corresponds with the time counter of the authentication server,