Patent ID: 6842493

Claim:
Procedure to increase the manipulation security for a bi-directional contactless data transmission by means of a first transmission and receiver unit (BA) and a second transmission and receiver unit (TR) wherein the second transmission and receiver unit (TR), on receipt of a transmitted electromagnetic signal (fULmod) from the first transmission and receiver unit (BA) as a received electromagnetic signal, will process the received electromagnetic signal, including conversion with regard to at least one selected physical quantity that characterizes the signal and modulation with data to form a response signal (fDLmod) and re-transmit the response signal to the first transmission and receiver unit (BA), and on receipt of the response signal (f″DLmod), the first transmission and receiver unit (BA) will convert this response signal with regard to the selected physical quantity thereof into a test signal (f″UL) such that this will compensate the conversion effected in the second transmission and receiver unit (TR), and in the first transmission and receiver unit (BA) a comparison between the test signal (f″UL) and the transmitted electromagnetic signal (fUL) is effected, and as a result (CF) of the comparison a value is assigned to a manipulation indication.