personal key pko of the official being enrolled alternatively pko can be selected at random from a list of unused pko 39 s and the list of available pko 39 s would thereby be diminished in yet another alternative pko could be accessed from a counter such as a pseudorandom or an ordinary sequential counter the output of which may be coded with a secret key the size or length of pko can be such as to provide a full size memory address or an offset or an index extension to limit or enlarge the memory space wherein concealed files are stored pko is then transmitted over the secure link to the enrollment terminal at the terminal the official enters his pin and name and various other information required by the system the name can be numerically coded by using a telephone type key pad the pin is applied to an irreversible coder 104 which produces his coded pin cpno cpno is applied as the key input to a coder 106 which receives pko as the data input the data output of coder 106 is the official 39 s coded personal key cpko which is applied as an input to mixer 107 the official 39 s name code and tin otin are also applied as inputs to mixer 107 cpko represents a coded address since.