z32check
v0.0.2
Published
z-base-32 checksum encoding
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z32check
z-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 z32check 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.
z32 Addresses
Specific to Blockstack, the Stacks blockchain uses z32-encoded public key hashes as addresses. Specifically, a z32 address is a z32-encoded ripemd160 hash, where the first character is capitalized (note that the z-base-32 alphabet does not have capital letters).
Examples
> z32 = require('z32check')
{ z32encode: [Function: z32encode],
z32decode: [Function: z32decode],
z32checkEncode: [Function: z32checkEncode],
z32checkDecode: [Function: z32checkDecode],
z32address: [Function: z32address],
z32addressDecode: [Function: z32addressDecode],
versions:
{ mainnet: { p2pkh: 22, p2sh: 11 },
testnet: { p2pkh: 17, p2sh: 2 } } }
z32encode, z32decode
> z32check.z32encode(Buffer.from('hello world').toString('hex'))
'decisga53yq7zzr5dr'
> z32check.z32decode('decisga53yq7zzr5dr')
'68656c6c6f20776f726c64'
> Buffer.from('68656c6c6f20776f726c64', 'hex').toString()
'hello world'
z32checkEncode, z32checkDecode
> version = 12
12
> z32check.z32checkEncode(version, Buffer.from('hello world').toString('hex'))
'cpb1sa5dxrb5s6huccoawk3ce'
> z32check.z32checkDecode('cpb1sa5dxrb5s6huccoawk3ce')
[ 12, '68656c6c6f20776f726c64' ]
> Buffer.from('68656c6c6f20776f726c64', 'hex').toString()
'hello world'
z32address, z32addressDecode
NOTE: these methods only work on ripemd160 hashes
> hash160 = 'a46ff88886c2ef9762d970b4d2c63678835bd39d'
'a46ff88886c2ef9762d970b4d2c63678835bd39d'
> version = z32check.versions.mainnet.p2pkh
22
> z32check.z32address(version, hash160)
'Sn1g96reo5bq9f5n5famjwsgg3hegs6uuia5jq18'
> z32check.z32addressDecode('Sn1g96reo5bq9f5n5famjwsgg3hegs6uuia5jq18')
[ 22, 'a46ff88886c2ef9762d970b4d2c63678835bd39d' ]