1. A method of administering public assistance programs for food purchases while eliminating the excessive costs, inefficiencies, fraud and waste associated with food stamps, said method comprising: issuing to each authorized recipient of public assistance for food purchases at least one card including (i) a recipient identifier encoded thereon, (ii) a photographic likeness of the recipient and (iii) an arrangement of numerals that encode and reveal a unique PIN when overlaid by an appropriate, current mask, with the photographic likeness and arrangement of numerals appearing on the same card; under the authority of the responsible social services agency, maintaining food assistance recipient account files that reflect the current account balance for each authorized recipient and periodically replenishing each account with new credit according to the prescribed allotment for the recipient; providing a plurality of masks to each food merchant, each mask being registerable over said arrangement of numerals to reveal a PIN; under authority of the responsible social services agency, notifying each food merchant on a periodic or random basis of the appropriate, then-current mask to be used in registration over cards to determine PINs during an identifiable period of time; carrying out each food purchase transaction between a food assistance recipient and food merchant by: (A) having the food merchant register the then-current mask over the arrangement of numerals on the recipient's card to reveal the unique then-current PIN, while compelling unsupervised merchant compliance regarding the identity of the card user versus the photographic likeness on the card and (B) providing a card processing station at each food merchant location and utilizing the station to input to a banking network (i) the recipient identifier, (ii) the debit charge associated with the purchase and (iii) the then-current PIN for the recipient as determined by utilization of the mask; approving or declining the transaction by determining the sufficiency of the recipient's account balance to cover the amount of the transaction.