We study lightweight and secure gambling methods, and propose a general framework that is secure against various "disconnection" and "payment refusal" attacks. Our method can be employed for single- and multi-player games in which players are independent, such as slot machines, roulette and blackjack. We focus on "open card" games, i.e., games where the casino's best game strategy is not affected by knowledge of the randomness used by the players (once both or all parties have committed to their random strings.) Our method allows players as well as casinos to ascertain that the game is played exactly according to the rules agreed oil. including that the various random events in fact are random. Given the low computational costs involved, we can implement the games on cellular phones, without concerns of excessive computation or power consumption.