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0021-ckb-address-format.md

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Number Category Status Author Organization Created
0021
Standards Track
Proposal
Cipher Wang
Nervos Foundation
2019-01-20

CKB Address Format

Abstract

CKB Address Format is an application level cell lock script display recommendation. The lock script consists of three key parameters, including code_hash, hash_type and args. CKB address packages lock script into a single line, verifiable, and human read friendly format.

Data Structure

Payload Format Types

To generate a CKB address, we firstly encode lock script to bytes array, name payload. And secondly, we wrap the payload into final address format.

There are several methods to convert lock script into payload bytes array. We use 1 byte to identify the payload format.

format type description
0x01 short version for locks with popular code_hash
0x02 full version with hash_type = "Data"
0x04 full version with hash_type = "Type"

Short Payload Format

Short payload format is a compact format which identifies common used code_hash by 1 byte code_hash_index instead of 32 bytes code_hash.

payload = 0x01 | code_hash_index | args

To translate payload to lock script, one can convert code_hash_index to code_hash and hash_type with the following popular code_hash table. And args as the args.

code_hash_index code_hash hash_type args
0x00 SECP256K1 + blake160 Type blake160(PK)*
0x01 SECP256K1 + multisig Type multisig script hash**
0x02 anyone_can_pay Type blake160(PK)

* The blake160 here means the leading 20 bytes truncation of Blake2b hash result.

** The multisig script hash is the 20 bytes blake160 hash of multisig script. The multisig script should be assembled in the following format:

S | R | M | N | blake160(Pubkey1) | blake160(Pubkey2) | ...

Where S/R/M/N are four single byte unsigned integers, ranging from 0 to 255, and blake160(Pubkey1) it the first 160bit blake2b hash of SECP256K1 compressed public keys. S is format version, currently fixed to 0. M/N means the user must provide M of N signatures to unlock the cell. And R means the provided signatures at least match the first R items of the Pubkey list.

For example, Alice, Bob, and Cipher collectively control a multisig locked cell. They define the unlock rule like "any two of us can unlock the cell, but Cipher must approve". The corresponding multisig script is:

0 | 1 | 2 | 3 | Pk_Cipher_h | Pk_Alice_h | Pk_Bob_h

Full Payload Format

Full payload format directly encodes all data field of lock script.

payload = 0x02/0x04 | code_hash | args

The first byte identifies the lock script's hash_type, 0x02 for "Data", 0x04 for "Type".

Wrap to Address

We follow Bitcoin base32 address format (BIP-173) rules to wrap payload into address, which uses Bech32 encoding and a BCH checksum.

The original version of Bech32 allows at most 90 characters long. Similar with BOLT, we simply remove the length limit. The error correction function is disabled when the Bech32 string is longer than 90. We don't intent to use this function anyway, because there is a risk to get wrong correction result.

A Bech32 string consists of the human-readable part, the separator, and the data part. The last 6 characters of data part is checksum. The data part is base32 encoded. Here is the readable translation of base32 encoding table.

0 1 2 3 4 5 6 7
+0 q p z r y 9 x 8
+8 g f 2 t v d w 0
+16 s 3 j n 5 4 k h
+24 c e 6 m u a 7 l

The human-readable part is "ckb" for CKB mainnet, and "ckt" for the testnet. The separator is always "1".

Examples and Demo Code

== short address (code_hash_index = 0x00) test ==
args to encode:          b39bbc0b3673c7d36450bc14cfcdad2d559c6c64
address generated:       ckb1qyqt8xaupvm8837nv3gtc9x0ekkj64vud3jqfwyw5v

== short address (code_hash_index = 0x01) test ==
multi sign script:       00 | 01 | 02 | 03 | bd07d9f32bce34d27152a6a0391d324f79aab854 | 094ee28566dff02a012a66505822a2fd67d668fb | 4643c241e59e81b7876527ebff23dfb24cf16482
args to encode:          4fb2be2e5d0c1a3b8694f832350a33c1685d477a
address generated:       ckb1qyq5lv479ewscx3ms620sv34pgeuz6zagaaqklhtgg

== full address test ==
code_hash to encode:     9bd7e06f3ecf4be0f2fcd2188b23f1b9fcc88e5d4b65a8637b17723bbda3cce8
with args to encode:     b39bbc0b3673c7d36450bc14cfcdad2d559c6c64
full address generated:  ckb1qjda0cr08m85hc8jlnfp3zer7xulejywt49kt2rr0vthywaa50xw3vumhs9nvu786dj9p0q5elx66t24n3kxgj53qks

Demo code: https://github.com/CipherWang/ckb-address-demo