the method enables the authorisation centre of a limited access system to determine whether a user desiring to gain access to the system via a remote terminal having local processing capacity is authorised to gain access or not , to authenticate the sender and verify the content of any information claimed to be sent by a user via a remote terminal and to ensure that any information sent by the authorisation centre to a user via a remote terminal may be accessed only by the user and may not be accessed by any unauthorised third person . the method is built upon the creation of one - time cryptographic keys and unique cryptographic algorithms in parallel at the authorisation centre and at the remote terminal using a common graphical symbol set generating algorithm known to the authentication centre and to the user plus a common cryptographic key generation algorithm and a common cryptographic algorithm generation process known to the authorisation centre and to the remote terminal .