A method for authenticating a client device into a network consistent with certain embodiments involves at a server device, generating a multi-digit random secret number; displaying the random secret number on a server display coupled to the server device; positioning the client device in close enough physical proximity to the server device to permit observation of the displayed random secret number; at the client device, sequentially entering each digit of the random secret number by actuation of a switch coupled to the client device a number of times equivalent to each digit of the random secret number; and upon correct entry of the random secret number at the client device, completing an authentication and key exchange process using the random secret number in an encryption and decryption process carried out at the server device and the client device. This abstract is not to be considered limiting, since other embodiments may deviate from the features described in this abstract.