Bitcoin Cash

driver

bitcoincash

curve

secp256k1

address formats

legacy P2PKH in CashAddr

SLIP-44 coin

145'

Load it

import { useBlockchain, blockchains } from "@agntn/keys";

const bchChain = useBlockchain(await blockchains.bitcoincash()());
const testnet = useBlockchain(await blockchains.bitcoincash({ network: "testnet" })());

Mainnet and testnet only, anything else throws in the constructor. Testnet3, testnet4, scalenet and chipnet all use the same bchtest prefix, so one testnet driver covers them.

The address

The hash is Bitcoin's, RIPEMD160(SHA256(pubkey)), byte for byte. Only the writing changes. A version byte goes in front, the whole thing is regrouped into 5-bit digits, and CashAddr adds a 40-bit checksum taken over the prefix too.

const privateKey = "0000000000000000000000000000000000000000000000000000000000000001";
const publicKey = bchChain.getKeyPublic(privateKey);

bchChain.getAddress(publicKey); // bitcoincash:qp63uahgrxged4z5jswyt5dn5v3lzsem6cy4spdc2h
testnet.getAddress(publicKey); // bchtest:qp63uahgrxged4z5jswyt5dn5v3lzsem6cq85x00dt

That's 1BgGZ9tcN4rm9KBzDn7KprQz87SZ26SAMH on Bitcoin, same key, same hash. The prefix is always written out, because that's the form wallets and explorers print.

legacy is the only type and it means pay to pubkey hash. It doesn't mean base58: the base58 form of that hash is a Bitcoin address, so the driver never produces it. Ask for "p2sh", "segwit" or anything else and getAddress throws a RangeError. Bitcoin's p2sh type wraps a segwit program, and there's no segwit on Bitcoin Cash, so a quiet fallback here could only lose money.

Validation

bchChain.validateAddress("bitcoincash:qp63uahgrxged4z5jswyt5dn5v3lzsem6cy4spdc2h"); // true
bchChain.validateAddress("qp63uahgrxged4z5jswyt5dn5v3lzsem6cy4spdc2h"); // true, prefix left off
bchChain.validateAddress("1BgGZ9tcN4rm9KBzDn7KprQz87SZ26SAMH"); // false, base58

It reads CashAddr the way Bitcoin Cash Node does. The prefix is optional. Upper or lower case works, a mix of both doesn't. The checksum is always computed under the driver's own prefix, so a testnet or eCash address fails like a typo would. Past the checksum, the version byte has to agree with the hash length, and the type and length have to be ones the node pays to: pubkey hashes over 20 bytes, script hashes over 20 or 32, plus the token-aware twins CashTokens added (z... and r...).

Base58 is refused even though the node still takes it. Its bytes say Bitcoin, and agntn/chains draws the same line.

Mnemonics

BIP32 on m/44'/145'/account'/change/index. The purpose level doesn't pick a format here the way it does on Bitcoin, since there's only one.

const mnemonic = "all all all all all all all all all all all all";

bchChain.deriveHDWallet(mnemonic, "m/44'/145'/0'/0/0").address;
// bitcoincash:qr08q88p9etk89wgv05nwlrkm4l0urz4cyl36hh9sv, what a Trezor shows for that seed

WIF is Bitcoin's too, prefix 0x80. encodeWIF(privateKey, { chain: "bitcoin" }) gives the string a Bitcoin Cash wallet imports.

Signing

Bitcoin Cash Node kept Bitcoin's "\x18Bitcoin Signed Message:\n", so the digest is identical: compact size lengths, double SHA-256, secp256k1. A Bitcoin Cash signature and a Bitcoin signature over the same key and message are the same 64 bytes of r||s hex. Like Bitcoin, { recovered: true } throws, because the node's recoverable form is base64 with a header byte.

Where it lives

src/blockchains/bitcoincash.ts has the prefixes and the address rules. It extends AbstractBitcoinMessageBlockchain in src/utils/bitcoin.ts, the part of the Bitcoin base with keys and signed messages and none of the address formats. The CashAddr codec is in src/utils/cashaddr.ts.