Proof is established by means of the following parameters: m pairs of private values Q1 and public values G1 m>1, a public module n made of the product of f first factors pj, f>2, a public exponent v, linked to each other by relations of the type: G1. The main circuit board has a surface with a plug connector and a receptacle connector mounted thereon. At least one of electric field amplitude and magnetic field amplitude at each of the sensors is recorded each time the transient electric field andor magnetic field is applied. The EMI shielding member is configured to engage a panel of the chassis to suppress the escape of EMI energy from the chassis.