Zcash WASM Scanning SDK

High-performance Rust-based WebAssembly SDK for Zcash. Provides efficient private transaction scanning (trial decryption) and key utilities for JavaScript/TypeScript environments (Node.js & Web).

Features

• High-Performance Scanning: Batch trial decryption for Orchard actions using WASM.
• Privacy Handling: Decrypt transaction specific details (memos, amounts) securely.
• Address Management: Parse Unified Addresses (UA).
• Cross-Platform: Works in both Browser and Node.js.

Installation

1. In this project (local dev)

# Build (required)
wasm-pack build --target nodejs --out-dir pkg-node

# Install deps
npm install

2. In an External Project

If you have published this package to NPM or are installing via git/local path:

# Install via NPM/pnpm/yarn
pnpm install zypherscan-zcash-wasm

Then import normally in your code:

import {
  get_addresses,
  batch_filter_compact_outputs,
} from "zypherscan-zcash-wasm";

Prerequisite: Building the SDK

To use this SDK in a Node.js environment (like the CLI scanner), build it with the nodejs target:

# Install wasm-pack
npm install -g wasm-pack

# Build for Node.js
wasm-pack build --target nodejs --out-dir pkg-node

Usage Example

1. Basic Setup & Scanning

import {
  batch_filter_compact_outputs,
  get_addresses,
} from "zypherscan-zcash-wasm";

async function main() {
  // 1. Setup Keys
  // Note: Addresses must be derived from a Unified Address string, not raw keys.
  const ua = "u1...";
  const addresses = JSON.parse(get_addresses(ua));
  console.log("Orchard Address:", addresses.orchard);

  // 2. Scan Compact Outputs (from Lightwalletd)
  const outputs = [
    {
      txid: "...",
      height: 123456,
      nullifier: "hex...",
      cmx: "hex...",
      ephemeral_key: "hex...",
      ciphertext: "hex...",
    },
  ];

  // match against your Viewing Key (UFVK)
  const ufvk = "uview...";
  const matchesJson = batch_filter_compact_outputs(
    JSON.stringify(outputs),
    ufvk
  );
  console.log("Matches:", JSON.parse(matchesJson));
}

2. Live Scanner CLI

This repository includes a fully functional CLI tool to scan the Zcash blockchain for transactions.

Setup:

# Install dependencies
npm install

# Build WASM
wasm-pack build --target nodejs --out-dir pkg-node

Run Scanner:

npm start

Follow the interactive prompts:

1. Lightwalletd URL: e.g., lightwalletd.zypherscan.com
2. UFVK: Your Unified Full Viewing Key.
3. Birthday Height: Block height to start scanning from.
4. Unified Address: (Optional) Your UA for display purposes.

API Reference

get_addresses(ua: string) -> string (JSON)

Parses a Unified Address and returns its component receivers (Orchard, Sapling, Transparent).

• Input: Unified Address string (u1...).
• Returns: JSON string { orchard: "...", sapling: "...", transparent: "..." }.

batch_filter_compact_outputs(json_outputs: string, ufvk: string) -> string (JSON)

Scans a batch of compact outputs to find those owned by the viewing key.

• Input: JSON array of compact output objects, UFVK string.
• Returns: JSON array of matches { txid: "...", index: ... }.

decrypt_memo(tx_hex: string, ufvk: string) -> string (JSON)

Decrypts a full transaction hex to retrieve amounts, memos, and directions.

• Input: Raw transaction hex, UFVK string.
• Output: JSON array of decrypted outputs.

License

MIT