Quick Start

Everything in this repository is working code. There are no placeholders, no “coming soon” sections, no hand-waving. The contracts are deployed on Soroban testnet. The tests pass. Start here and have something running in under 5 minutes.

Prerequisites

Install the following before proceeding:

# Rust + WebAssembly target
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
rustup target add wasm32v1-none

# Stellar CLI (version 27 or later)
# macOS
brew install stellar-cli
# Linux
cargo install --locked stellar-cli

# Node.js 20+
# https://nodejs.org/

# Bun 1.1+ — bitcoin-script, relayer, frontend and packages/* install with Bun,
# not npm. Only circuits/ is npm-managed.
curl -fsSL https://bun.sh/install | bash

# circom (for ZK circuit tests only).
# circom 2.x is a Rust binary. `npm install -g circom` installs the legacy 1.x
# package and CANNOT compile `pragma circom 2.0.0` — use the release binary:
curl -fL -o ~/.local/bin/circom \
  https://github.com/iden3/circom/releases/download/v2.2.3/circom-linux-amd64
chmod +x ~/.local/bin/circom   # macOS: use circom-macos-amd64
circom --version               # expect: circom compiler 2.2.3

# snarkjs needs no global install — it is a dependency of circuits/

Clone the Repository

git clone https://github.com/WritzProtocol/writz.git
cd writz

Run All Tests

Soroban contracts (Rust)

cd contracts
cargo test

Expected output: 146 tests pass across bitcoin-spv (47), zk-verifier (18), commitment-tree (18), and private-lend (63).

Bitcoin script toolkit (TypeScript, Bun)

cd bitcoin-script
bun install
bun test

Expected output: 60 tests pass.

Relayer service (TypeScript, Bun install + Jest)

The relayer installs with Bun but its suite is Jest (ts-jest), so it must run through the package script — plain bun test selects Bun’s own runner and fails. It also imports the local @writz/* packages via their built dist/ output, so build those first.

cd packages/commitment-tree && bun install
cd ../../bitcoin-script && bun run build
cd ../relayer && bun install && bun run test

Expected output: 48 tests pass.

ZK circuits (Circom + snarkjs, npm)

cd circuits
npm install
npm test

Expected output: 20 tests pass (proof generation, commitment correctness, ratio enforcement, nullifiers).

All together: 274 tests, all passing.

Build the Contracts

cd contracts
stellar contract build

This produces Wasm artifacts in contracts/target/wasm32v1-none/release/:

bitcoin_spv.wasm — 28.4 KB
zk_verifier.wasm — 11.8 KB
commitment_tree.wasm — ~38 KB
private_lend.wasm — 23.7 KB

Use the Testnet Deployments

All four contracts are live on Soroban testnet. You can call them directly without deploying:

# Check the SPV contract is alive
stellar contract invoke \
  --id CAE5L7BO2GNF7MIZWXB2BTUMLYNIMQZUSWN2BWLZQS7HRHLOUSL6VLWJ \
  --network testnet \
  -- get_version

# Check the Merkle root
stellar contract invoke \
  --id CC2OZ3LG5U6RE3U7QC2R5QMID5GHQBE7QXTJQ4ZSTP5W73WDTKQPRW7E \
  --network testnet \
  -- get_merkle_root
# Returns: 0x2134e76ac74b4b8765b6e37992aa15f0... (Poseidon-2 empty tree root)

Run the Full ZK End-to-End Flow

This script runs the complete deposit → borrow → repay cycle on Soroban testnet using the deployed contracts. It generates real ZK proofs and submits them on-chain.

# You need a Stellar testnet key with XLM and USDC
# Get testnet XLM: https://laboratory.stellar.org/#account-creator?network=test

WRITZ_DEV_SECRET=<your-testnet-secret-key> node scripts/deploy/e2e_zkflow.js

This script:

Initializes the commitment-tree contract with a USDC pool
Supplies 1,000 USDC to the pool
Generates a Groth16 deposit proof (circom WASM)
Submits the SPV proof + ZK proof → commitment created on-chain
Inserts the commitment into the Merkle tree (Poseidon root updated)
Generates a Groth16 borrow proof (150% collateral ratio enforced)
Submits the borrow → 200 XLM transferred from pool
Generates a Groth16 repay proof (field-negation amount recovery)
Submits the repay → debt cleared

All 6 transactions land on testnet. You can verify them on Stellar Expert (testnet).

Run the Bitcoin P2WSH End-to-End

This script tests the Bitcoin locking and release flow on Bitcoin Signet. No funds required for a dry run.

cd bitcoin-script
npm run build

# Dry run — builds and inspects the P2WSH transaction without broadcasting
node scripts/e2e_testnet.mjs --dry-run

# Live broadcast (requires Signet BTC — get from a Signet faucet)
node scripts/e2e_testnet.mjs

The live broadcast will:

Generate a unique P2WSH address
Send Signet BTC to the address
Build the Path A co-signed release transaction
Sign with both user and protocol keys (PSBT round-trip)
Broadcast to Bitcoin Signet

Reference transactions (already executed on Bitcoin Signet):

Funding: 61deea44
Release: 11932100

Deploy Your Own Contracts

If you want to deploy fresh contract instances to testnet:

cd contracts

# Build
stellar contract build

# Deploy bitcoin-spv
stellar contract deploy \
  --wasm target/wasm32v1-none/release/bitcoin_spv.wasm \
  --source <your-account> \
  --network testnet

# Deploy zk-verifier
stellar contract deploy \
  --wasm target/wasm32v1-none/release/zk_verifier.wasm \
  --source <your-account> \
  --network testnet

# Initialize the zk-verifier with verification keys
node scripts/deploy/set_vkeys.js \
  --verifier <zk-verifier-contract-id> \
  --network testnet \
  --secret <your-secret>

# Deploy commitment-tree
stellar contract deploy \
  --wasm target/wasm32v1-none/release/commitment_tree.wasm \
  --source <your-account> \
  --network testnet

See contracts/deployments/testnet.md for the full init sequence and verified transaction hashes.

Repository Layout for Developers

contracts/
  contracts/
    bitcoin-spv/src/
      lib.rs        — public contract interface
      header.rs     — Bitcoin block header parsing + PoW verification
      merkle.rs     — Merkle proof verification
      crypto.rs     — SHA256d implementation in Soroban Wasm
      types.rs      — BitcoinBlockHeader, VerificationResult
    zk-verifier/src/
      lib.rs        — verify_groth16(), set_vkey()
    commitment-tree/src/
      lib.rs        — deposit(), borrow(), repay(), liquidate()
      oracle.rs     — SEP-40 oracle interface
    private-lend/src/
      lib.rs        — non-ZK lending skeleton
      rates.rs      — kinked interest rate model

circuits/
  src/
    deposit.circom      — Deposit ZK circuit
    borrow_repay.circom — Borrow/Repay ZK circuit
    liquidation.circom  — Liquidation ZK circuit
    merkle.circom       — Shared Poseidon Merkle components
  keys/
    deposit.vkey.json       — Deposit verification key
    borrow_repay.vkey.json  — Borrow/Repay verification key
    liquidation.vkey.json   — Liquidation verification key

relayer/src/
  index.ts      — Express API: GET /spv-proof/:txid
  spv.ts        — SPV proof assembly (Esplora + Merkle computation)
  bitcoin.ts    — Bitcoin types and parsing

bitcoin-script/src/
  script.ts     — P2WSH redeem script builder
  address.ts    — Deposit address derivation
  spend.ts      — Path A/B PSBT signing
  keys.ts       — Key management utilities

Next: Bitcoin SPV SDK →

​Quick Start

​Prerequisites

​Clone the Repository

​Run All Tests

​Soroban contracts (Rust)

​Bitcoin script toolkit (TypeScript, Bun)

​Relayer service (TypeScript, Bun install + Jest)

​ZK circuits (Circom + snarkjs, npm)

​All together: 274 tests, all passing.

​Build the Contracts

​Use the Testnet Deployments

​Run the Full ZK End-to-End Flow

​Run the Bitcoin P2WSH End-to-End

​Deploy Your Own Contracts

​Repository Layout for Developers