| Applications include gambling (especially lottery games), quizzes, and to conceal PINs for telephone calling cards and other prepaid services. In some cases, the entire scratchable area needs to (or may be) scratched to see whether a prize has been won, or to reveal the secret code; the result for the cardholder does not change based on what portions are scratched off or not. In other cases, selected areas have to be scratched; this may apply in a quiz, where the area corresponding to the right answer is scratched, or in gambling, where depending on which areas are scratched one wins or loses. In these cases the card becomes invalid if too many areas are scratched. After losing one can scratch all areas to see if, how, and what one could have won with this card. Such cards are vulnerable to attack by devices which allow individuals to see through the concealing substance without physically disturbing it. |
