Hunting the Wolf - ZK Game

A deduction game where a wolf hides among sheep and a shepherd tries to find it, using zero-knowledge proofs (ZK) to keep the wolf's identity hidden.

Game Concept

Hunting the Wolf is a game where one player (the wolf) disguises as a sheep and another player (the shepherd) tries to find it among the other sheep. The game implements zero-knowledge proofs to keep the wolf's identity private, adding a layer of cryptographic security to the game.

Game Mechanics

1. Game Start:

   • A board with 16 sheep is generated, each with an assigned number.
   • The wolf chooses a sheep to hide its identity and sends a cryptographic commitment that keeps its choice secret.

2. Rounds:

   • In each round, the wolf must select an adjacent sheep to kill, verified through ZK proofs.
   • The sheep appears dead on the board.
   • The shepherd marks a sheep as suspicious.
   • The wolf generates a ZK proof that verifies whether the marked sheep is the wolf or not, without revealing its identity.
   • If the marked sheep is the wolf, the round ends. If not, the sheep dies and the game continues.

3. End:

   • After 3 rounds, players swap roles (the shepherd becomes the wolf and vice versa).
   • The game ends after 6 total rounds (3 for each role).
   • The score is based on the number of sheep each player managed to eliminate.
   • The player with the highest score wins.

Privacy System

The game implements two main ZK circuits:

1. kill_sheep: Verifies that:

   • The wolf is who it claims to be (matches the commitment)
   • The sheep to be killed is adjacent to the wolf (horizontally, vertically, or diagonally)
   • The sheep to be killed is alive

2. is_wolf: Verifies that:

   • The wolf's commitment is valid
   • The marked sheep is alive
   • Whether the marked sheep is the wolf or not

Privacy Flow

1. Wolf's initial commitment:

   • The wolf chooses a sheep and generates a random value (salt) that is saved in localStorage
   • Creates a commitment using the Poseidon function: poseidon([wolf_sheep_number, wolf_salt])
   • Only this hash is published on the blockchain, keeping the wolf's identity secret

2. Sheep's death:

   • The wolf selects an adjacent sheep to kill
   • Generates a ZK proof with the kill_sheep circuit
   • The sheep dies and is saved in the contract

3. Shepherd's selection of the suspicious sheep:

   • The shepherd selects a suspicious sheep
   • This selection is saved in the contract

4. The wolf generates a ZK proof to verify if the marked sheep is the wolf:

   • The wolf's frontend is waiting for the shepherd to mark a sheep as suspicious
   • Generates a ZK proof with the is_wolf circuit
   • The ZK proof is sent to the contract

5. Wolf verification:

   • The contract verifies the ZK proof and determines the result
   • The result (1=is wolf, 0=is not wolf) is obtained without revealing the wolf's identity
   • Only if the wolf is found (result=1), the round ends
   • If the wolf is not found, the game is saved for the next round