Bech32(m) Encoding for Arbitrary Buffers

Bech32 is a Bitcoin address format specified in BIP 173 and BIP 350. Among its advantages are: better adaptability to QR codes and in voice conversations, and improved error detection. This library generalizes Bech32 and its modified version (Bech32m) to encode any reasonably short byte buffers.

Usage

Encoding data

1declare function encode(
2  prefix: string,
3  data: Uint8Array,
4  encoding: 'bech32' | 'bech32m' = 'bech32'
5): string;

Encodes binary data with the specified human-readable prefix into a Bech32(m) string. The case is preserved: if the prefix is uppercase, then the output will be uppercase as well; otherwise, the output will be lowercase (including the case when the prefix does not contain any letters).

Arguments

• prefix: string
  Human-readable prefix to hint what kind of data Bech32 encodes. Must contain ASCII chars in the range 33-126
• data: Uint8Array
  Binary data to encode
• encoding: bech32 or bech32m
  Specifies whether to use the original Bech32 encoding from BIP 173 or the modified encoding from BIP 350; they differ in how a checksum is computed. If omitted, the original encoding is used.

Return value

String containing:

1. prefix
2. '1' separator char
3. data encoded with the variant of base32 encoding used by Bech32, and
4. 6-char checksum calculated based on prefix and data

Example

1const bech32 = require('bech32-buffer');
2const data = new Uint8Array(20);
3bech32.encode('test', data);
4// 'test1qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqql6aptf'

Decoding data

1declare function decode(message: string): {
2  prefix: string,
3  encoding: 'bech32' | 'bech32m',
4  data: Uint8Array
5};

Extracts human-readable prefix and binary data from the Bech32-encoded string.

Arguments

• data: string
  String to decode

Return value

An object with the following fields:

• prefix: string
  Human-readable prefix
• encoding: bech32 or bech32m
  Encoding variant inferred from the checksum.
• data: Uint8Array
  Binary data encoded into the input string

Decoding may fail for a variety of reasons (e.g., invalid checksum, or invalid chars in the input). In this case, decode() throws an exception with a descriptive message.

Example

1const bech32 = require('bech32-buffer');
2const data = 'lost1qsyq7yqh9gk0szs5';
3bech32.decode(data);
4// {
5//   prefix: 'lost',
6//   encoding: 'bech32',
7//   data: Uint8Array([ 4, 8, 15, 16, 23, 42 ])
8// }

Bitcoin addresses

1declare class BitcoinAddress {
2  prefix: 'bc' | 'tb';
3  scriptVersion: number;
4  data: Uint8Array;
5
6  static decode(message: string): BitcoinAddress;
7  constructor(prefix: 'bc' | 'tb', scriptVersion: number, data: Uint8Array);
8  encode(): string;
9  type(): void | 'p2wsh' | 'p2wpkh';
10}

Provides basic functionality to work with Bech32 encoding of Bitcoin addresses. Addresses can be decoded from strings and encoded into strings. It is also possible to check the type of an address. P2WSH and P2WPKH address types are defined per BIP 141. Encoding constraints are defined per BIP 173 and BIP 350.

Example

1const { BitcoinAddress } = require('bech32-buffer');
2const address = BitcoinAddress.decode('BC1QW508D6QEJXTDG4Y5R3ZARVARY0C5XW7KV8F3T4');
3// address.prefix === 'bc'
4// address.scriptVersion === 0
5// address.data.length === 20
6// address.type() === 'p2wpkh'

Use in Browsers

Use dist/bech32-buffer.min.js from the package distribution or your favorite browserifier. In the first case, the library will be available as a bech32 global variable:

1<script src="bech32-buffer.min.js"></script>
2<!-- later -->
3<script>
4bech32.encode('test', new Uint8Array(20));
5</script>

Check out the web demo to see how bech32-buffer works in browser. It is also available in the examples directory of the package.

Acknowledgements

BIP 173 is authored by Pieter Wuille and Greg Maxwell and is licensed under the 2-clause BSD license. BIP 350 is authored by Pieter Wuille and is licensed under the 2-clause BSD license.

There are at least 2 existing implementations of Bech32 for JavaScript:

• The reference implementation by Pieter Wuille
• Another implementation available as the bech32 package

Both implementations are Bitcoin-specific, and the reference implementation is also not in the Npm / yarn package manager.

License

bech32-buffer is available under Apache-2.0 license.