In a process for ensuring the data integrity of software for influencing operation of a control unit of a motor vehicle, a pair of keys is provided for encrypting and decrypting electronic data. The first key is stored for access by a control unit in the motor vehicle, and software which is to be imported is signed by means of the second key. The signed software is imported into the memory of the control unit and the signature of the software is checked by means of the first key. The signature is accepted if the check has a positive result.