In a control system comprising control device adapted for, on the one hand, receiving signal indicating a first biometric datum (W), and, on the other hand, obtaining a second biometric datum captured (w′), at the level of the control device, the first and second biometric date are compared. Next, it is decided whether the first and second biometric data correspond on the basis of the comparison. Thereafter, at least a secret cryptographic key part (H(w)) is generated by applying cryptographic function to the first biometric datum.