The game of SNARKs (and STARKs later)

HODL the door!

Description and rationale

During the ETHBerlin we've tried to make a good demonstration of the power of zkSNARKs by implementing a "Battleships" game where an interaction between the players is governed by the SNARKs. During the development we understood that it's actually is quite abstract two-party state-channel with some kind of a smart-contract inside. Keeping the state updates is expensive in the mainnet, so such interaction can be moved to Plasma, where the operator verifies SNARKs upon transaction submissions and updates a "state". Many people forget that Plasma was introduced not only as L2 solution for payments, but also as kind of map-reduce system.

Other repositories related to this work, developers were working in their own repos or reusing the current R&D code:

• Gadget lib for libsnark developed by the Matter Inc. is here. (test_branch branch)
• Smart-contracts that are for game setup and further fraud proofs from Plasma operator - here.
• Simple UI brought to you here.
• Backend assembled here (current repo).

Limitations

Due to a huge pain of building a libsnark anywhere but Linux this repo contains a binary assembled under Ubuntu16.04, that is called through the command line(!) from the Go backend. In principle Go backend is ready to verify proofs itself, it's just a matter of pain with proof serialization.

How to run

Keep in mind the limitations above!

• go get github.com/shamatar/go-snarks
• cd $GOPATH/src/github/shamatar/go-snarks
• go run -v ./main.go
• open your browser at http://127.0.0.1:8080/public/index.html
• place the ships. Right now limits are hardcoded - 4 ships 1x1, 3 ships 1x2, 2 ships 1x3, 1 ship 1x4
• if you made a mistake - reload a page
• if you have placed ships properly (in the right amounts and without adjustency) - click a "submit" button to send the position to the backend to make a proof of the correct positioning
• if you did make a mistake - you will see an error in a window below
• if your position was correct you will see a quasi-serialized proof. You can either click "verify" to verify it at the backend, or change one of the big numbers (not zeroes!) there and click "verify" and get a negative result - you have corrupted a proof and it's not longer valid
• right now commitment to the position is not produced, just the position in verified

That's all for now

Intended functionality

• zkSNARK that proves the correctness of position
• produce a salted commitment to position (used further as a public input)
• create a smart-contract for players to start a game
• make a zkSNARK for a state updates, that checks turns one by one
  • check whos turn it is now
  • check the signature of the current player (for shooting)
  • check that position under the commitment is correct
  • if there is a "hit" - update the corresponding score
  • keep the history of shots and don't allow duplicates
  • update the scores
  • have a win condition
• bring further state updates to Plasma
• implement fraud proofs

Much work to do!

Authors (team)

Alex Vlasov, shamatar

Konstantin Panarin, Konstantce

Artem Vorobyev, artall64