How to Use Bitcoin to Play Internet Poker

We present practical protocols for playing poker over the internet without having to trust a third party. Our poker protocols are dropout-tolerant in the sense that any party that drops out during the middle of the game is forced to pay a monetary penalty to all other parties. More generally, we introduce and design protocols for secure cash distribution with penalties, a primitive that simultaneously generalizes secure computation with penalties of Bentov and Kumaresan (Crypto 2014), and secure lottery with penalties of Andrychowicz et al. (Security and Privacy 2014). Since secure cash distribution with penalties is a reactive functionality by design, it suffices to capture a wide variety of card games (including poker), board games, and auctions. Our protocol realizing secure cash distribution with penalties works in a hybrid model where parties have access to a claim-or-refund transaction functionality F CR which can be efficiently realized in (a variant of) Bitcoin.