Bitcoin

driver

bitcoin

curve

secp256k1

address formats

legacy, p2sh, segwit, p2wsh, taproot

SLIP-44 coin

0'

Load it

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

const bitcoinChain = useBlockchain(await blockchains.bitcoin()());
const testnetChain = useBlockchain(await blockchains.bitcoin({ network: "testnet" })());

Or import the class directly from @agntn/keys/blockchains/bitcoin and call new Bitcoin().

Five formats

const publicKey = bitcoinChain.getKeyPublic(privateKey);

bitcoinChain.getAddress(publicKey); // 1...
bitcoinChain.getAddress(publicKey, "p2sh"); // 3...
bitcoinChain.getAddress(publicKey, "segwit"); // bc1q...
bitcoinChain.getAddress(publicKey, "taproot"); // bc1p...

bitcoinChain.generateWallet({}, "segwit"); // whole wallet, segwit address

Legacy and p2sh both start from RIPEMD160(SHA256(pubkey)). p2sh wraps that hash in a 0 <20 bytes> redeem script and hashes again. Segwit puts the same 20 bytes behind witness version 0. Taproot is the real thing: the x only key gets tweaked with TapTweak per BIP341, so the address matches what Bitcoin Core derives for a key path spend, not a shortcut that only looks right.

Validation

bitcoinChain.validateAddress("1BvBMSEYstWetqTFn5Au4m4GFg7xJaNVN2"); // true
bitcoinChain.validateAddress("3J98t1WpEZ73CNmQviecrnyiWrnqRhWNLy"); // true
bitcoinChain.validateAddress("bc1qw508d6qejxtdg4y5r3zarvary0c5xw7kv8f3t4"); // true
bitcoinChain.validateAddress("bc1p0xlxvlhemja6c4dqv22uapctqupfhlxm9h8z3k2e72q4k9hcz7vqzk5jj0"); // true

The prefix picks the decoder, then the checksum has to hold. A mainnet driver rejects testnet addresses and the other way round, which is what you want and occasionally what surprises you in a test.

Mnemonics

deriveHDWallet reads the BIP43 purpose when you do not pass an address type:

bitcoinChain.deriveHDWallet(mnemonic, "m/84'/0'/0'/0/0").address; // bc1q..., segwit from purpose 84
bitcoinChain.deriveHDWallet(mnemonic, "m/86'/0'/0'/0/0").address; // bc1p..., taproot from purpose 86
bitcoinChain.deriveHDWallet(mnemonic, "m/44'/0'/0'/0/0", {}, "segwit"); // explicit type wins

Purpose 44 is legacy, 49 is p2sh, 84 segwit, 86 taproot. Anything else with no explicit type falls back to legacy.

Signing

signMessage hashes with the "\x18Bitcoin Signed Message:\n" preamble, the same one Bitcoin Core uses, and signs with secp256k1. The result is a hex signature that verifyMessage checks against the public key. It is not the base64 recoverable format bitcoin-cli signmessage prints, so do not paste one into the other.

Where it lives

src/blockchains/bitcoin.ts holds the network table and the type dispatch. The hashing and encoding helpers sit in src/utils/address.ts and src/utils/encoding.ts, shared with TRON and the custom chain example.