Patent ID: 7543154

Claim:
A method for a computer determining an access code with a predetermined number of input symbols, comprising: inputting the input symbols at a plurality of input positions in an input field that is at least two-dimensional, a number of the input positions being larger than the predetermined number of input symbols; determining the access code from the input symbols, respective input positions at input of the input symbols, and an input sequence of input data; arranging said input field as an at least two dimensional matrix of cells; arranging a plurality of possible input positions in each of said cells; and linearizing the input field to form a 1×N array that forms the access code, wherein: the access code has a plurality of entries, each of the plurality of entries corresponding to each of the plurality of possible input positions irrespective of whether an input symbol has been input at each of the plurality of possible input positions; and N is an integer greater than 1.