CAIP-4: Blockchain Reference for the BIP122 Namespace Source

Author Simon Warta, ligi, Pedro Gomes
Status Superseded
Type Standard
Created 2019-12-05
Updated 2020-01-16
Requires 2
Superseded By

Simple Summary

This document is about the details of the BIP122 namespace and reference for CAIP-2.


In CAIP-2 a general blockchain identification scheme is defined. This is the implementation of CAIP-2 for BIP122 (Bitcoin).


See CAIP-2.


BIP122 Namespace

The namespace is called “bip122” as in BIP122.

Reference Definition

The definition is delegated to BIP122’s chain ID definition. The format is a 32 character prefix of the block hash from BIP122 (lower case hex).

Resolution Method

To resolve a blockchain reference for the BIP122 namespace, make a JSON-RPC request to the blockchain node with method getblockhash, for example:

// Request
  "id": 1,
  "jsonrpc": "2.0",
  "method": "getblockhash",
  "params": [0]

// Response
  "id": 1,
  "jsonrpc": "2.0",
  "result": "000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f"

The response will return as a value for the result a hash for the block with height 0 that should be sliced to its first 16 bytes (32 characters for base 16) to be CAIP-4 compatible.


We delegate the identification of Bitcoin-like chains to BIP122, as this is the best Bitcoin chain identification standard known to the authors of this CAIP.

Backwards Compatibility

Not applicable

Test Cases

This is a list of manually composed examples

# Bitcoin mainnet (see

# Litecoin

# Feathercoin (Litecoin fork)

Copyright and related rights waived via CC0.


Please cite this document as:

Simon Warta, ligi, Pedro Gomes, "CAIP-4: Blockchain Reference for the BIP122 Namespace," Chain Agnostic Improvement Proposals, no. 4, December 2019. [Online serial]. Available: