Zecraft

A game engine for fair, private games on shielded Zcash. Build one in a weekend.

Live: zecraft-production.up.railway.app: the testnet raffle, with every past round verifiable in your browser.

What it is

• An open-source Rust engine, with a WebAssembly verifier that runs in the browser.
• You write a game's rules in three functions: classify, settle, board.
• Zecraft handles the rest: rounds, private entries, drand draws, a 2-of-3 FROST vault, sealed payouts to fresh addresses, and public verification.

Proof it works

• The raffle runs live on testnet at zecraft-production.up.railway.app. Press "Verify round 0 yourself": your browser fetches the chain data and runs all five checks (about 12 s).
• The first live raffle round settled on Zcash testnet: round 0, payout transaction 2c3b07f1c2ea033f7c331a54ec9c49e5de9840a98141137923002154782e4922. All five verification checks pass: proof bundle, verifier output.
• A second game, the coin flip, runs through the full engine in the tests. Its entries are settled, a FROST-signed payout is approved by a keyholder and mined, and all five checks pass (coinflip_e2e.rs).

Quickstart

env -u RUSTFLAGS cargo build --release -p zecraft-cli
target/release/zecraft new mygame
env -u RUSTFLAGS cargo test --release -p zecraft-mygame

zecraft new dice creates:

games/dice/README.md
games/dice/game-params.json
games/dice/rules/Cargo.toml
games/dice/rules/src/lib.rs        <- your game: edit the lines marked YOUR GAME
games/dice/rules/tests/dice.rs     <- tests that pass out of the box
games/dice/server/Cargo.toml
games/dice/server/src/bin/zecraft-dice-{engine,keyholder,verify}.rs

Then follow docs/BUILD_A_GAME.md to run it on testnet.

env -u RUSTFLAGS matters: .cargo/config.toml sets the NU7 testnet flag, and an exported RUSTFLAGS would override it.

How a round works

1. Enter. Players pay the vault with a shielded memo that names the round, carries the entry, and seals a fresh payout address.
2. Close. The round's window of 24 blocks closes.
3. Draw. A drand beacon published after the reveal delay (15 minutes on testnet) supplies the randomness. If block times can't prove the round closed first, it is voided and refunded.
4. Settle. The game's rules turn the round into payouts. The engine checks that value is conserved.
5. Sign. Each keyholder recomputes the round itself, checks the payout transaction, and signs only if it matches. Two of three FROST signatures pay it.
6. Verify. Anyone can recheck a round: the five checks run in the browser or with zecraft-<game>-verify round <n>.

Privacy, honestly

Private: who entered, which entries belong to the same person, and who won. Public by design: each entry's amount and ticket count, and every payout amount, via the published testnet viewing key, so anyone can verify the draw.

Known limits

• One operator. In the local and hosted demo, one person runs all three keyholders. The hosted raffle runs them in one Railway container (deploy/railway). Production needs independent operators on separate machines.
• One testnet server. No independent testnet lightwalletd answers right now. The verifier re-checks every proof and signature itself, but its chain data comes from one server.
• Testnet only.

Games built with Zecraft

Game	Status
Raffle	Live on testnet: zecraft-production.up.railway.app
Coin flip	Example, and the zecraft new template
Zeek	The game Zecraft was extracted from: playzeek.pages.dev, github.com/shrooms08/zeek

Repo layout

Path	What
crates/zecraft-core	Pure rules: chain params, drand draw, entry memos, the Rules trait, proof bundles
crates/zecraft-engine	Round server: follows the chain, settles, coordinates payouts, serves the API and page
crates/zecraft-keyholder	FROST keyholder that re-checks every payout before signing
crates/zecraft-verify	The five checks (native CLI and wasm)
crates/zecraft-vault, crates/zecraft-player	FROST vault wallet; test player wallet
crates/zecraft-cli	zecraft new
games/	Raffle (rules, server, wasm, web page) and coin flip
scripts/local/, config/, docs/	Local testnet runner, the raffle's public config, guides and examples

Roadmap

• A browser wallet module, from Zeek Pocket.
• Independent keyholder operators.
• A second testnet lightwalletd for verification.
• More game templates.
• Mainnet, after review.
• A rename to zblock (links will redirect).

Funding testnet

Get TAZ from fauzec.com. The valargroup faucet currently can't pay NU7 addresses.

Licence

MIT OR Apache-2.0, as Zeek (LICENSE-MIT, LICENSE-APACHE). Extracted from Zeek: see PROVENANCE.md.