Coding method for an electronic key.

p0001The invention relates to a method for code protection in an electronic key, particularly for motor vehicles with built-in central locking, which consists of a transmitter which transmits a coded infrared signal which is received by a matched to the code receiver, the code of the signal at the transmitter and receiver is adjustable.

p0002In such systems which are based on the encoding of a signal on the transmitter side and the decryption of this signal on the receiver side, Besht the danger that can be-stored received and the coded signal from any receiver when the latter during the transmission process in the beam area the transmitter is located. So relatively easily can be produced a copy of the electronic key, whereby an unauthorized use of a motor vehicle is made possible.

p0003The copying facilities described can be prevented only if the transmitter and receiver are brought together so close that a second receiver is not in the transmitter beam area. However, this is not practically possible in motor vehicles, since the receiver is arranged in the interior of the vehicle while the transmitter is outside the vehicle. Through reflections, for example an_den discs, thus there is a danger that the transmitted signal, even at near-approach, is scattered and can be taken illegally from a second receiver.

p0004An electronic key of the aforementioned kind is known from DE-A-29 06 665th The well-known key has to adjust the code on the transmitter and receiver switch groups, whereby the code by the user can be set. It is hereby in principle possible, that the user sets a new code on the device after each unlocking, however, there is one hand the danger that the code on the transmitter and receiver is tuned differently, whereby the vehicle can no longer be open and on the other hand, it contradicts the convenient handling of such electronic locks, so that is generally set a new code only when change of ownership of the vehicle.

p0005The object of the invention is to provide a method of code protection in an electronic key, the guaranteed in a simple manner in that the electronic key can not be used by unauthorized persons.

p0006This object is achieved with the method mentioned in the present invention by the use of a random generator, which selects an arbitrary bit patterns from the number of code possibilities and the transmitter and receiver, preferably by a forced synchronization, transmitted.

p0007Hereby the advantage is achieved that from the large number of options, for example, at 24 bits 2 = 16 million, an arbitrary image pattern is selected. An unlawful use of copied code is praktisch.ausgeschlossen so. Preferably, the exchange of information of the valid code by means of a forced synchronization, which is achieved for example in that the transmitter and receiver are interconnected electronic. This happens for example the fact that the transmitter and receiver are assembled in the vehicle, so that other functions, such as switching on the ignition, be guaranteed. Thus, advantageously takes place after each unlocking action a. Readjustment of the code.

p0008According to one embodiment of the invention, the transmitter sends after a battery change a reset code, which ensures that the electronic lock can be opened in any case.

p0009Another embodiment provides that the lowering of the operating voltage of the receiver below a certain level by a self-hold circuit as relays, a latch is actuated, which allows unlocking with a mechanical key.

p0010This ensures that a motor vehicle can also be opened if, for example, has forgotten to turn off the light, and thus the battery voltage is no longer sufficient for operation of the receiver.

p0011Incidentally, when changing the battery in the receiver is also connected to the reset code, as when changing the battery in the transmitter, start, or it can be transmitted by a forced synchronization of the next valid code of the random generator to the receiver or to the transmitter.

p0012Another embodiment of the method is that several belonging to a receiver stations receive an identifier, and that the valid for each transmitter code is stored in the receiver. This is achieved the advantage that, for example, for a vehicle more keys may be issued and still maintaining the benefits of coding with the random generator for each individual key.

p0013It is also possible that a manufacturer who supplies various clients, the key series each customer provides you with a specific identifier, so that the same bit pattern of the code for different customers actual applicable.

p0014Preferably, the inventive method works DER. art that are generator random selected encoding options used by only for unlocking that is sent but for the lock respectively the same code. For this purpose, the transmitter can either be equipped with a control button which operated alternately functions "on" or "to". However, it can be arranged for this purpose on the transmitter, two different keys. The sending of the reset code can for example be done by one of the buttons is pressed for a longer time.

p0015Another advantage of the invention is, for example, that when handing over the vehicle to the workshop, the lock is opened electronically and can be operated with the mechanical key way. that the electronic key remains in the user's hand.

p0016Another advantageous possibility is that both the sender and receiver are provided with an automatic stepping system which exchange the code cyclically if by any mistake the forced synchronization is omitted. This ensures that a copy of the code uses even in case anything if, for example, only the vehicle is geöffet without it put into operation, so that a forced synchronization has not taken place. In this case, otherwise there would be the possibility that using a copied signal an unlawful use place-able.

p0017The identification of each transmitter of the plurality of transmitter / receiver combinations can be carried out in the manner of a selector switch, which is described for example in the DE-U-80 05 555th The selector switch can be made at the manufacturer of a punch which cuts the corresponding Codiereingänge. In this way, a characteristic image pattern is formed that is read when initializing each to start the entire program to the key-specific site for the code. The license code is expediently simultaneously reset or "door" code. Thus also a unique assignment is possible with Schlüsselnachbestellung; they shall be assessed for spilled key electronically by sending the signal, eg "door".

p0018The invention is illustrated by the embodiment shown in the drawing.

p0019In the single figure, which shows a block diagram of an electronic key, at 1 is a transmitter and designated 2 of the accompanying end receiver. Conveniently, there are transmitter 1 and receiver 2 of one CMOS microprocessor with subsequent amplifier 3 and 7, and infra-red transmitting diode 4 or phototransistor 6. The transmitter 1 sends on the photodiode 4, the encoded infrared signal 5 from that received by the Fctotransistor 6 and over the amplifier 7 is fed to the receiver manager. 2 At the output 8 of the receiver 2 a control signal 9, with the central locking of the vehicle is operated appear.

p0020The space required for the inventive method random can be easily realized using the already-existing microprocessors and accommodate either the transmitter 1 or the receiver. 2