c32check

c32check

Crockford base-32 encoding library with 4-byte checksum.

This library is meant for generating and decoding Stacks addresses on the Blockstack blockchain.

How it works

Each c32check string encodes a 1-byte version and a 4-byte checksum. When decoded as a hex string, the wire format looks like this:

0      1                             n+1             n+5
|------|-----------------------------|---------------|
version     n-byte hex payload          4-byte hash

If version is the version byte (a 1-byte number) and payload is the raw bytes (e.g. as a string), then the checksum is calculated as follows:

checksum = sha256(sha256(version + payload)).substring(0,4)

In other words, the checksum is the first four bytes of the double-sha256 of the bytestring concatenation of the version and payload. This is similar to base58check encoding, for example.

c32 Addresses

Specific to Blockstack, the Stacks blockchain uses c32-encoded public key hashes as addresses. Specifically, a c32check address is a c32check-encoded ripemd160 hash.

Examples

> c32 = require('c32check')
{ c32encode: [Function: c32encode],
  c32decode: [Function: c32decode],
  c32checkEncode: [Function: c32checkEncode],
  c32checkDecode: [Function: c32checkDecode],
  c32address: [Function: c32address],
  c32addressDecode: [Function: c32addressDecode],
  versions: 
   { mainnet: { p2pkh: 22, p2sh: 20 },
     testnet: { p2pkh: 26, p2sh: 21 } } }

c32encode, c32decode

> c32check.c32encode(Buffer.from('hello world').toString('hex'))
'38CNP6RVS0EXQQ4V34'
> c32check.c32decode('38CNP6RVS0EXQQ4V34')
'68656c6c6f20776f726c64'
> Buffer.from('68656c6c6f20776f726c64', 'hex').toString()
'hello world'

c32checkEncode, c32checkDecode

> version = 12
12
> c32check.c32checkEncode(version, Buffer.from('hello world').toString('hex'))
'CD1JPRV3F41VPYWKCCGRMASC8'
> c32check.c32checkDecode('CD1JPRV3F41VPYWKCCGRMASC8')
[ 12, '68656c6c6f20776f726c64' ] 
> Buffer.from('68656c6c6f20776f726c64', 'hex').toString()
'hello world'

c32address, c32addressDecode

NOTE: these methods only work on ripemd160 hashes

> hash160 = 'a46ff88886c2ef9762d970b4d2c63678835bd39d'
'a46ff88886c2ef9762d970b4d2c63678835bd39d'
> version = c32check.versions.mainnet.p2pkh
22
> c32check.c32address(version, hash160)
'SP2J6ZY48GV1EZ5V2V5RB9MP66SW86PYKKNRV9EJ7'
> c32check.c32addressDecode('SP2J6ZY48GV1EZ5V2V5RB9MP66SW86PYKKNRV9EJ7')
[ 22, 'a46ff88886c2ef9762d970b4d2c63678835bd39d' ]