Abstract: A driving authorization system comprises an electronic immobilizer function which is coupled to a rotary shaft sensor. The rotary shaft sensor senses the position and/or rotational speed of the rotary shaft by means of a pickup wheel arranged on a rotary shaft, and transmits that information to a vehicle control unit which enables the electronic immobilizer function. According to the invention, the pickup wheel comprises a predefined number of teeth which are arranged distributed along the circumference of the pickup wheel according to a code, and an encoded rotational speed signal which is picked up by the rotary shaft sensor and can be decoded by the vehicle control unit. The vehicle control unit enables the immobilizer function only after successful decoding of the encoded rotational speed signal. A synchronization time for detecting a specific position of the rotary shaft is part of the encoded rotational speed signal.