In a bi-directional contactless data transmission, a procedure aims to prevent the communication distance from being extended by unauthorized persons using radio repeaters. The procedure involves establishing a fixed relationship of a selected physical parameter of an electromagnetic signal. For example,...http://www.google.es/patents/US6842493?utm_source=gb-gplus-sharePatente US6842493 - Procedure for increasing the manipulation security for a bi-directional contactless data transmission
Procedure for increasing the manipulation security for a bi-directional ...
