bitcoin-spv proof fetcher

The following clients are provided to fetch Bitcoin data to create proofs.

Clients

• BcoinClient

BcoinClient

Use the BcoinClient fetch Bitcoin data from a bcoin node. See the bcoin docs for how to run your own node.

Install

Node.js:

$ npm i --save @summa-tx/bitcoin-spv-js-clients

const { BcoinClient } = require('@summa-tx/bitcoin-spv-js-clients');

ES6 module:

import { BcoinClient } from '@summa-tx/bitcoin-spv-js-clients';

Use

The BcoinClient proof fetcher exports a single constructor function, BcoinClient, which accepts an options Object to configure the client. This constructor is an extension of bcoin's NodeClient. See bcoin.io for more information about how to configure the client.

const options = {
  network: 'testnet',
  port: 18332,
  apiKey: 'api-key'
};

const client = new BcoinClient(options);

Methods

client.getBlockHeader(block)

• @param {Hash|Number} block
• @returns {Promise}

Retrieve a block header.

const client = new BcoinClient(options);
const blockHeader = await client.getBlockHeader(150151);

// block header
// {
//   "hash": "6f1003edd05cad861395225415160b5236968cc223fe982796b6e959c9651d44",
//   "version": 536870912,
//   "prevBlock": "0c4ea5e675941eca1909275f21903cef755069a03c57c10f4d4dadcdd7146daf",
//   "merkleRoot": "9a249c682aba07943c8a1f9bd774a15d71372fcd7f3f9ee99e8c7aa022ae6aa0",
//   "time": 1571661863,
//   "bits": 545259519,
//   "nonce": 8,
//   "height": 100,
//   "chainwork": "00000000000000000000000000000000000000000000000000000000000000ca"
// }

client.getProof(txid)

• @param {String} txid - txid in big endian
• @returns {Object} - proof object

Get a proof for a transaction.

const client = new BcoinClient(options);
const txid =

// proof object
// {
//   version: {String},
//   vin: {String},
//   vout: {String},
//   locktime: {String},
//   tx_id: {String},
//   index: {Number},
//   confirming_header: {Object},
//   intermediate_nodes: {String}
// }

client.getHeader(block)

• @param {Hash|Number} block - block height or hash
• @returns {Object} header - header object

Gets header by height or hash.

const client = new BcoinClient(options);
const block = 12345;
const header = client.getHeader(block);

// {
//   raw: {String},
//   hash: {String},
//   height: {Number},
//   prevhash: {String},
//   merkle_root: {String},
// }

client.getMerkleProof(txid, height)

• @param {String} txid
• @param {Number} height
• @returns {[][]String, Number} - a merkle proof and the index of the leaf

Validate the merkle tree of a block and then compute a merkle proof of inclusion for the txid.

const client = new BcoinClient(options);
const height = 12345;
const txid = '3a4324234'
const header = client.getMerkleProof(txid, height);

// merkle proof
// [
//   '8e2d404a039a7a3e1768b161aa23546aab0444b73905bdd3d68b3d6f1769e8c0...',
//   4
// ]

client.getHeaderChainByCount(height, count, enc)

• @param {Number} height - starting block height
• @param {Number} count - number of headers
• @param {String} enc - 'json' or 'hex' or 'btcspv'
• @returns {Object}

Fetch a header chain by count.

const client = new BcoinClient(options);
const height = 12345;
const numOfHeaders = 2;
const encoding = 'hex';
const header = client.getHeaderChainByCount(height, numOfHeaders, encoding);

// headers (hex)
// {
//   headers: '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...'
// }

const header = client.getHeaderChainByCount(height, numOfHeaders, 'json');

// headers (json)
// {
//   headers: [
//     {
//       "hash": "6f1003edd05cad861395225415160b5236968cc223fe982796b6e959c9651d44",
//       "version": 536870912,
//       "prevBlock": "0c4ea5e675941eca1909275f21903cef755069a03c57c10f4d4dadcdd7146daf",
//       "merkleRoot": "9a249c682aba07943c8a1f9bd774a15d71372fcd7f3f9ee99e8c7aa022ae6aa0",
//       "time": 1571661863,
//       "bits": 545259519,
//       "nonce": 8,
//       "height": 100,
//       "chainwork": "00000000000000000000000000000000000000000000000000000000000000ca"
//     },
//         {
//       "hash": "6f1003edd05cad861395225415160b5236968cc223fe982796b6e959c9651d44",
//       "version": 536870912,
//       "prevBlock": "0c4ea5e675941eca1909275f21903cef755069a03c57c10f4d4dadcdd7146daf",
//       "merkleRoot": "9a249c682aba07943c8a1f9bd774a15d71372fcd7f3f9ee99e8c7aa022ae6aa0",
//       "time": 1571661863,
//       "bits": 545259519,
//       "nonce": 8,
//       "height": 100,
//       "chainwork": "00000000000000000000000000000000000000000000000000000000000000ca"
//     },
//   ]
// }