czinn / pydice

An implementation of the game Liar's Dice in Python using an almost-P2P protocol.

pydice

An implementation of the game Liar's Dice in Python using an almost-P2P protocol.

pydice uses a concept called Mental Poker. It allows a game with hidden information and randomness to be played without a central authority (e.g. a server) keeping track of information.

The Commitment Schema

The commitment schema (or protocol) goes something like this (with Hash(x) being some hash function):

1. Each player picks a secret number K and computes C = Hash(K) and D = Hash(C)
2. Each player reveals D to all other players.
3. Each player reveals C to all other players, who can verify that D = Hash(C). This ensures that players didn't change their C in response to other players revealing their values.
4. All revealed Cs are added together in some commutative way to get S.
5. Each player calculates Hash(C + S) (all players can do this for all other players) to obtain the turn ordering for the round.
6. Each player privately calculates R = Hash(K + S). R is the player's private value; in Liar's Dice, it's used to generate their set of dice.
7. After the round, each player reveals K and R, and other players can verify that this matches their commitment C.