c32check

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

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

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 } },
c32ToB58: [Function: c32ToB58],
b58ToC32: [Function: b58ToC32] }
`

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' ]
`

c32ToB58, b58ToC32

> Note:
> Common address versions are converted between c32check and base58check
> seamlessly, in order to accommodate Stacks addresses.

`
> b58addr = '16EMaNw3pkn3v6f2BgnSSs53zAKH4Q8YJg'
'16EMaNw3pkn3v6f2BgnSSs53zAKH4Q8YJg'
> c32check.b58ToC32(b58addr)
'SPWNYDJ3STG7XH7ERWXMV6MQ7Q6EATWVY5Q1QMP8'
> c32check.c32ToB58('SPWNYDJ3STG7XH7ERWXMV6MQ7Q6EATWVY5Q1QMP8')
'16EMaNw3pkn3v6f2BgnSSs53zAKH4Q8YJg'
`

`
> b58addr = '3D2oetdNuZUqQHPJmcMDDHYoqkyNVsFk9r'
'3D2oetdNuZUqQHPJmcMDDHYoqkyNVsFk9r'
> c32check.b58ToC32(b58addr)
'SM1Y6EXF21RZ9739DFTEQKB1H044BMM0XVCM4A4NY'
> c32check.c32ToB58('SM1Y6EXF21RZ9739DFTEQKB1H044BMM0XVCM4A4NY')
'3D2oetdNuZUqQHPJmcMDDHYoqkyNVsFk9r'
``