1. A method carried out by an authentication system using a user interface having a display for receiving input of a security token by a user protecting a resource to be used by the user, comprising: generating a hint display made up of elements arranged in an array; providing a predetermined pattern in the array of selected ones of the elements of the array; each element in the predetermined pattern having a unique position characteristic in the array; at least one of the elements in the predetermined pattern having a numerical value; displaying said hint display to said user; causing said user to compute a token from said elements of said predetermined pattern of elements of said generated hint display; during computing of the token causing said user to perform at least one operation on said numerical value of said at least one of said elements falling within said predetermined pattern such that the token comprises at least one hidden numerical value which is not identical to the numerical value of said at least one of said elements upon which the non-identity operation is performed; causing said user to enter the token into the user interface; receiving said token from said user in which the token comprises at least one character; and comparing said at least one hidden numerical value of the token received with at least one corresponding numerical value of a corresponding token generated by the authentication system; and selectively providing access to said resource in conformity with a matching result of said comparing.