The present invention relates to a method to authenticate a user using an authenticator at an access device using another registered device named personal device, said authenticator being stored by the access device after registration of the personal device comprising a double encryption using an access device's secret key and a personal device's public key to be retrieved at each request of authentication received from the personal device, encrypted using a session key and sent with the session key encrypted using the personal device's public key to the personal device for partial decryption using the decrypted session key and the personal device's private key, re-encryption using the session key and sending back to the access device for total decryption of the authenticator, using the session key and the access device's secret key, and use of the thus decrypted authenticator to authenticate at the access device.