Portable libraries for transparent → shielded Zcash transactions

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t2z enables existing transparent-only Zcash infrastructure to send to shielded Orchard addresses without requiring a full wallet implementation. Built on the PCZT (Partially Constructed Zcash Transaction) format.

✨ Features

• 🔐 Privacy upgrade path — Send from transparent inputs to shielded Orchard outputs
• 📦 PCZT format — Multi-party transaction construction, hardware wallet support
• ⚡ No downloads — Orchard uses Halo 2, proving key built on demand (~10s, cached)
• 🦀 Battle-tested — Built on official Zcash Rust libraries

📦 Available SDKs

Platform	Package	Status
TypeScript	@d4mr/t2z-wasm	✅ Available
Go	github.com/d4mr/t2z/sdks/go	✅ Available (build from source)
Kotlin	com.d4mr:t2z	✅ Available (build from source)

🚀 Quick Start

npm install @d4mr/t2z-wasm

import * as t2z from '@d4mr/t2z-wasm';

// 1. Create the transaction
let pczt = t2z.propose_transaction(
  [new t2z.WasmTransparentInput(
    pubkeyHex,           // 33-byte compressed pubkey
    prevoutTxidLE,       // Previous tx ID (little-endian)
    0,                   // Output index
    1_000_000n,          // 0.01 ZEC in zatoshis
    scriptPubkeyHex,     // P2PKH script
    null                 // Sequence (default)
  )],
  [new t2z.WasmPayment(
    'u1recipient...',    // Unified address with Orchard
    900_000n,            // Amount in zatoshis
    null,                // Memo (hex)
    null                 // Label
  )],
  'u1change...',         // Change address
  'testnet',             // Network
  3720100                // Expiry height
);

// 2. Sign transparent inputs (external signing supported)
const sighash = t2z.get_sighash(pczt, 0);
const signature = await yourSigner.sign(sighash);  // Hardware wallet, HSM, etc.
pczt = t2z.append_signature(pczt, 0, pubkeyHex, signature);

// 3. Generate Orchard proofs
pczt = t2z.prove_transaction(pczt);

// 4. Finalize and broadcast
const txHex = t2z.finalize_and_extract_hex(pczt);
await broadcast(txHex);

📖 Documentation

• Full Documentation — Guides, API reference, examples
• Live Demo — Interactive transaction builder
• API Reference — Complete function docs

🔧 Transaction Flow

┌─────────┐    ┌────────┐    ┌──────┐    ┌───────┐    ┌──────────┐
│ Propose │───▶│ Verify │───▶│ Sign │───▶│ Prove │───▶│ Finalize │
└─────────┘    └────────┘    └──────┘    └───────┘    └──────────┘
                (optional)

1. Propose — Create PCZT from inputs and payments
2. Verify — Validate PCZT matches request (if from third party)
3. Sign — Add signatures for transparent inputs
4. Prove — Generate Orchard ZK proofs
5. Finalize — Extract raw transaction for broadcast

🏗️ Project Structure

t2z/
├── crates/
│   ├── t2z-core/        # Core Rust library
│   ├── t2z-wasm/        # WebAssembly bindings
│   └── t2z-uniffi/      # Go/Kotlin bindings (UniFFI)
├── demo/                # Interactive demo (React + Vite)
└── docs/                # Documentation (Mintlify)

🛠️ Building from Source

Prerequisites

• Rust (nightly toolchain)
• wasm-pack
• LLVM (for WASM compilation)

macOS

# Install LLVM and wasi-libc
brew install llvm
brew install --HEAD aspect-build/aspect/wasi-libc

# Add wasm32 target
rustup target add wasm32-unknown-unknown

# Build the WASM package
cd crates/t2z-wasm
CC="$(brew --prefix llvm)/bin/clang" \
  AR="$(brew --prefix llvm)/bin/llvm-ar" \
  RUSTUP_TOOLCHAIN=nightly \
  wasm-pack build --scope d4mr

Linux

# Install dependencies (Ubuntu/Debian)
sudo apt install clang lld

# Add wasm32 target
rustup target add wasm32-unknown-unknown

# Build
cd crates/t2z-wasm
RUSTUP_TOOLCHAIN=nightly wasm-pack build --scope d4mr

The built package will be in crates/t2z-wasm/pkg/.

📚 Related

• ZIP 374: PCZT Specification (Draft)
• ZIP 317: Proportional Fee Mechanism
• ZIP 244: Transaction Signature Validation
• ZIP 321: Payment Request URIs

📄 License

MIT © d4mr