janken-solidity

operation flow

create a game by Player1(the host)

Generate a secret in a cryptographically secure way and hash it with your chosen hand. You need to remember the secret to prove correctness later. Also, need to send ether with that transaction as a deposit.

createGame(hostEncryptedHand, { value: web3.utils.toWei('1'), from: host })

how to generate encrypted hand

// chose your hand in Rock: 1, Paper: 2, Scissors: 3
const hand = 1;
// this `secret` is necessary for a step that reveals your hand so you need to make a note.
const secret = web3.utils.soliditySha3({ type: 'bytes32', value: crypto.randomBytes(32).toString('hex') });
const encryptedHand = web3.utils.soliditySha3({ type: 'uint', value: hand }, { type: 'bytes32', value: secret });

join the game by Player2(the opponent)

Commit the hand in the same way as the host. The transaction requires you to send the same amount of ether as host's deposit.

joinGame(gameId, opponentEncryptedHand, { value: web3.utils.toWei('1'), from: opponent })

note

You can join a game only if deadlineToJoin is not past.

reveal the hand you commited before

Reveal the not encrypted hand by sending it together with the secret used for encryption before.

revealHand(gameId, hostHand, hostSecret, { from: host })
revealHand(gameId, opponentHand, opponentSecret, { from: opponent })

note

If you don't reveal your hand by the time of deadlineToReveal, you will lose your all deposit.

withdraw funds deposited by the two (if you win!)

withdraw(gameId, { from: opponent })

rescue the deposit (optional)

There are two situations in which you can execute resuce(). The first situation is when you are a host of a game that no one has joined by deadlineToJoin. The second one is when you reveal a hand but your opponent doesn't reveal by deadlineToReveal. deadlineToJoin and deadlineToReveal are set a term of a day in default.

rescue(gameId, { from: host })

See run.js for more details.

run through in your console

npx truffle develop

truffle(develop)> migrate --reset
truffle(develop)> exec scripts/run.js
Using network 'develop'.

host =>
  handInt: 1,
  encryptedHand: 0xf307279d3fe9b98cbf0514a3de81e4e2c7465ea4c3893527ec105629e31f4959,
  secret: 0xbf5631c9938a1638afad2e1ba2439fe8b7e7d6410957a05c1b60ed8536373203
gameId =>  1
opponent =>
  handInt: 2,
  encryptedHand: 0x9b9d9d35bfd420b9c7e860583927b1773583caca81c75b0326d48ea2ecd66cd9,
  secret: 0x740ce4b15f0ed6433d4d981f33ba2b3bff4d32f2b9cb3eb277b005bed19519fc
result =>
    beforeBalance: 98995848940000000000,
    afterBalance: 100995330380000000000,
    delta: 1999481440000000000,
    fee: 518560000000000,
    deltaWithoutFee: 1998962880000000000

compile and run on remix

Go to https://remix.ethereum.org, and copy and paste Jankein.sol in Remix. You need to do one thing to compile and run on Remix, fix import statement about SafeMath.sol like below diffs.

-import "openzeppelin-solidity/contracts/math/SafeMath.sol";
+import "github.com/OpenZeppelin/openzeppelin-solidity/contracts/math/SafeMath.sol";

Deployment may fail. Raise the amount of Gas Limit on Remix and try again.

run tests

./test.sh