Device for theft protection based on an exchange of data which is partly representative of at least one authorized user of an automotive vehicle

The reception assembly (10) has a tunnel (24) for insertion of a badge (14) which contains user information exchanged through a transponder. A bistable badge blocking mechanism (44) with spring (52), pin (48) and electromagnet (50) provides a stable badge position for running and an unstable position for starting and an ejection position for stopping is actuated by a lever (54) and linkage (58,60)