Transmission-reception system

Details Transmission-reception system Transmission-reception system

1996-11-15

1998-12-01

Cain, David

Cryptography

Particular algorithmic function encoding

Nbs/des algorithm

380 49, H04K 100

Patent

active

058449906

ABSTRACT:
The invention relates to a transmission-reception system, particularly a transmitter-receiver device contained in the bow of an ignition key. When a resonance circuit receives a carrier wave signal from a transmission-reception ECU of a motor vehicle, a microcomputer is switched to an active state by the output of a power circuit that smoothes and rectifies the carrier wave signal. A detector circuit discriminates an enquiry signal supplied together with the carrier wave signal through the resonance circuit portion, and outputs the signal to the microcomputer. In response to the enquiry signal together with random number data, the activated microcomputer changes the bit length of an identification code stored in an EEPROM, on the basis of the received random number data and a predetermined function, and performs the on-off control of an FET of a modulating circuit in a mode corresponding to the bit length-changed identification code. The microcomputer thus performs control to send back an enciphered answer signal to the transmission-reception ECU.

REFERENCES:
patent: 5055701 (1991-10-01), Takeuchi
patent: 5420925 (1995-05-01), Michaels
patent: 5506905 (1996-04-01), Markowski et al.

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