Patent ID: 7841528

Claim:
Secure communication system between a contactless card reader and a card, said reader being adapted for transmitting an electromagnetic radiofrequency communication signal addressed to said card located in the near field and said card being adapted for transmitting a response message which is to be protected against an undesirable detection, the reader detecting the response signal by means of a first antenna and the reader comprising a circuit for generating a disturbance signal to create a disturbance signal at the same time as the response signal is transmitted by the card, wherein the circuit for generating the disturbance signal is able to transmit a disturbance signal with the same frequency and modulation type characteristics as the response signal expected from the card to the reader, said circuit for generating a disturbance signal comprising a second radiofrequency transmission antenna, separate from the first antenna, for transmitting the disturbance signal, the electromagnetic coupling between the two antennas being such that the first antenna retransmits to the reader mainly the response from the card but not the disturbance signal.