WiP: NightMarket

A zero knowledge marketplace for Dark Forest coordinates. A 0xParc Learning Group project - work in progress.

Quicklinks

• Spec & Brainstorm notes
• Demo slides

Quickstart

• Install: yarn install
• Test circuits: yarn circom:test
• Deploy circuits: yarn circom:prod
• Format verifier contracts: yarn sol:verify
• Compile contracts: yarn sol:compile

Directory

• /circuits/list: Circuits for generating a coordinate listing
• /circuits/sale: Circuits for fulfilling a sale to buyer
• /circuits/utils: Shared utility circuits
• /circuits/test: Circuit unit tests
• /client: Dark Forest plugin code
• /contracts: Contract and verifier code

Spec

• Sellers list any valid Dark Forest coordinates at a fixed price
• Multiple buyers can purchase these coordinates
• Sellers can attest their planet has certain biomes

Circuit Design

LIST

Prove: Seller has (x,y) coords, and sell a KEY used to encrypt it

• hash(XY,PLANETHASH_KEY) ==> valid_coord // I know a valid data/coordinate
• ENCODE(XY, KEY) // I encrypted data with key
• hash(KEY) // I commit to the secret key

SALE

Prove: Seller encrypted KEY with a SHARED_KEY from a ECDH key exchange with Buyer

• SHAREDKEY <== ecdh(sellerPrivKey, buyerPubKey) // An ECDH shared key
• ENCODE(KEY, SHARED_KEY) // Encrypt KEY, s.t. buyer can decrypt offline
• hash(KEY) ==> output // I encrypted the correct key
• BUYER_PUBKEY ==> output // I used the correct buyer key

ENCODE

Scheme: Encryption using a 5-wide Poseidon in SpongeWrap with (0, len=2, Kx ,Ky , N) as input.

• List:
  • message[0] = planet x coordinate
  • message[1] = planet y coordinate
  • key[0] = left half of key being sold
  • key[1] = right half of key being sold
• Sale:
  • message[0] = key[0]
  • message[1] = key[1]
  • key[0] = k_x of shared key
  • key[1] = k_y of shared key

Escrow Contract

• list(..., listProof, price, escrowTime): sellers can list valid coordinates and vary price & escrowTime for better buyer UX. (Note: it prevents malicious-buyer race condition). Sellers can sell a single coordinate to multiple buyers.
• delist(...): sellers can delist coordinates if they plan to be offline. This helps with seller reputation as this zk marketplace has to be interactive.
• ask(...): buyers can create (duplicate) orders on listings and lock up a payment for escrowTime blocks.
• sale(..., saleProof): sellers can close a sale and fulfill a buyer order.
• refund(...): anyone can refund buyers deposit if seller delists or if the escrowTime lockup is over.

Acknowledgements

• 0xParc for study group
• DF plugins
• DF Circuits
• EthMarketPlace
• Maci
• Poseidon Encryption, Paper