supernovahs / board-game

Board-Game

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This is a board game where every player's location is hidden . Everytime they move, they give a hint about there location. Guess the correct location and get rewarded or DIE!!!.

This game is powered by zero knowledge proofs.

Contents

• Stack Used
• Structure
  • circuits
  • frontend
  • contracts
• Running Locally
• How to Play

Stack

• Frontend :

  • Nextjs
  • Tailwindcss
  • chakraUi
  • snarkjs
  • Canva
  • wasm

• Circuits:

  • circom by iden3

  Circuits are written in a lang called circom. This language helps prove expressions that are either:

  • Constant values - Only a constant value is allowed. Ex: 4
  • linear expressions - Expression where only addition is used Ex: 4+7+7
  • Quadratic expressions - Expression where two linear expression are multiplied and one is added. Ex: a*b +c

• Contracts:

  • Solidity
  • Foundry Tests(To be completed)

Structure

• circuits : This folder consists of the 3 circom files that are used in the game :

  • Register.circom
  • Move.circom
  • Defend.circom

• contracts : This folder contains the core game contract and the verifier contracts generated using circom.

  • Game.sol
  • Registerverifier.sol
  • Moveverifier.sol
  • Defendverifier.sol

• frontend : Frontend is created using next js with wagmi hooks to connect to wallet .

  Zk proofs are generated in front end using the following files:

  • Defend.wasm
  • Defend_0001.zkey
  • Move.wasm
  • Move_0001.zkey
  • Register.wasm
  • Register_0001.zkey
  • Proofs.js

Configuring Locally

If you to experience the process yourself, here's how you can use this repository locally in your computer.

Deploying contracts

cd Game
cd contracts

npx hardhat run scripts/deploy.js --network networkName

Circuits

cd Game 
cd circuits

NextJs Frontend

Deploy on localhost :3000

cd Game
cd frontend
yarn dev

How to Play!

Your Goal in the Game?

Guess another player's location and attack , if successful your health increases, else vice versa. ERC20 token can be added for this.

• Register as a player : After connecting the wallet, you land on the register page, you enter the coordinates of the location you want to land. You can choose between 0 to 10.

• Register Circuit

    signal  input a; User enter x coordinate
    signal  input b; User enters Y coordinate
    signal input salt; 
    // User enters the zone he is entering, We will verify this below
    signal input zone; User enters zone 
    signal output c; This is the location hash that will be updated in contract

Here above , the zone input is public , because we want it to be public. All other inputs are private. The player enters the coordinate in front end , they are saved in local storage.

• Move : Player can move across the board by clicking on the buttons. Your location is private . Only the location hash is public in the contract. Your actual location is in your localstorage.

• Move circuit

    signal input x1;  // User enter the previous location x coordinate
    signal input y1;  // User enter the previous location y coordinate

    signal input x2;  // User enter the new location x coordinate where he moves
    signal input y2;  // User enter the new location y coordinate where he moves

    signal input salt; // Salt must be the same that was used to register
    signal input zone; // Zone will be public(Same as register)

    signal output a;  // Old  location hash(This will be verified in contract )
    signal output b;  // New location hash

If location is hashed, how will I guess another person's location?

Well, the Board Game is divided in 10 zones, when every player moves, a public variable named zone is updated based on the location of the player. This is achieved by zk proofs.

• Attack If you think you correctly guessed another player's location , Guess his location and click on attack.

• Defend If you're attacked you cannot move until you prove that your location in response to the attack.

Importance of Salt and some assumptions

To prevent Brute force attacks(i.e by guessing location using hit and trial), the player along with the coordinates submit a salt(it's a random number ) to the circuit to prevent attacks.

• Assumption

Almost every zk application has an assumption that the user knows his salt . The salt is saved in his local storage. If the player deleted his salt, he can not play the game. He will have to re register