Abstract: A method and a circuit of generation of several secret quantities by an integrated circuit according to the destination of these secret quantities, consisting of taking into account a first digital word forming a single identifier of the integrated circuit chip and coming from a physical parameter network, and of individualizing this identifier according to the application.

Abstract: A method and apparatus for determining the distance separating an electromagnetic transponder from a terminal generating a magnetic field by a first oscillating circuit, the transponder including a second oscillating circuit, upstream of a rectifying circuit adapted to providing a D.C. voltage. The method includes storing a first information relative to the level of the D.C. voltage when the second oscillating circuit is tuned on a determined frequency; storing a second information relative to the level of the D.C. voltage after having caused a frequency detuning of the second oscillating circuit; and comparing the two stored pieces of information.