BCSwiftFoundation

A collection of useful primitives for cryptocurrency wallets.

Opinionated Swift wrapper around LibWally.

Supports particular enhancements used by Blockchain Commons from our fork of libwally-core: bc-libwally-core, in the bc-maintenance branch.

Dependencies

Depends on BCSwiftWally, which is a thin wrapper around LibWally that has a new build system for building a universal XCFramework for use with MacOSX, Mac Catalyst, iOS devices, and the iOS simulator across Intel and Apple Silicon (ARM).

Building

Add to your project like any other Swift Package.

Usage

Derive address from a seed:

import BCFoundation

let mnemonic = BIP39(mnemonic: "abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon about")!
let seed = BIP39.Seed(bip39: mnemonic, passphrase: "bip39 passphrase")
let masterKey = try! HDKey(bip39Seed: seed)
assert(masterKey.keyFingerprint.hex == "7b343b65")
let path = DerivationPath(string: "m/44'/0'/0'")!
let accountKey = try! HDKey(parent: masterKey, childDerivationPath: path)
assert(accountKey.base58PrivateKey == "xprv9z3bixmawU269r5jUAbWbVFDY3qN6LZdHH7r28C7gmZMXPfbN8o39622JvuyvQxBYPBMEtJNetWBCyy6hZXcAEubReyb95MnJQR5bAMiR2d")
assert(accountKey.base58PublicKey == "xpub6D2x8UJUmqaPNLACaC8WxdBx65frVoHUeW3SpWbjF76LQBzjug7HgtLWACEbNoRubqXqM9y7t822g9RpEPPxmALG8tiZYVw5Ec66swihmUy")
assert(Bitcoin.Address(hdKey: accountKey, type: .payToWitnessPubKeyHash).description == "bc1qtqq3hzwgswm56tt3h04ss8qmmttt6py9yj8h6c")

Derive address from an xpub:

import BCFoundation

let accountKey = try! HDKey(base58: "xpub6ASuArnXKPbfEwhqN6e3mwBcDTgzisQN1wXN9BJcM47sSikHjJf3UFHKkNAWbWMiGj7Wf5uMash7SyYq527Hqck2AxYysAA7xmALppuCkwQ")
let receivePath = DerivationPath(string: "0/0")!
let receiveKey = try! HDKey(parent: accountKey, childDerivationPath: receivePath)
let address = Bitcoin.Address(hdKey: receiveKey, type: .payToPubKeyHash)
assert(address.description == "1BiCdXSDHyeXSzmx2paVPFVTrmyx7BeCGD")
assert(address.scriptPubKey.description == "pkh:[OP_DUP OP_HASH160 757c05317fcb85e910c5f3e6cd9dc4d06b5d8321 OP_EQUALVERIFY OP_CHECKSIG]")

Parse an address:

import BCFoundation

let address = Bitcoin.Address(string: "bc1q6zwjfmhdl4pvhvfpv8pchvtanlar8hrhqdyv0t")!
assert(address.scriptPubKey.hex == "0014d09d24eeedfd42cbb12161c38bb17d9ffa33dc77")
assert(address.scriptPubKey.type! == .wpkh)
assert(address.scriptPubKey.description == "wpkh:[OP_0 d09d24eeedfd42cbb12161c38bb17d9ffa33dc77]")

Create and sign a transaction:

import BCFoundation

let pubKey = ECCompressedPublicKey(hex: "03501e454bf00751f24b1b489aa925215d66af2234e3891c3b21a52bedb3cd711c")!
let prevTx = TxHash(hex: "0000000000000000000000000000000000000000000000000000000000000000")!
let vout: UInt32 = 0
let legacyInputBytes: Int = 192
let amount1: Satoshi = 1000 + Satoshi(legacyInputBytes)
let scriptSig = ScriptSig(type: .payToPubKeyHash(pubKey))
let scriptPubKey1 = ScriptPubKey(hex: "76a914bef5a2f9a56a94aab12459f72ad9cf8cf19c7bbe88ac")!
let txInput1 = TxInput(prevTx: prevTx, vout: vout, amount: amount1, sig: .scriptSig(scriptSig), scriptPubKey: scriptPubKey1)
let hdKey = try! HDKey(base58: "xprv9wTYmMFdV23N2TdNG573QoEsfRrWKQgWeibmLntzniatZvR9BmLnvSxqu53Kw1UmYPxLgboyZQaXwTCg8MSY3H2EU4pWcQDnRnrVA1xe8fs")
let txOutput = TxOutput(scriptPubKey: scriptPubKey1, amount: 1000)
let tx1 = Transaction(inputs: [txInput1], outputs: [txOutput])
let signedTx = tx1.signed(with: [hdKey])!
assert(signedTx.inputs![0].isSigned)
assert(signedTx.description == "01000000010000000000000000000000000000000000000000000000000000000000000000000000006a47304402203d274300310c06582d0186fc197106120c4838fa5d686fe3aa0478033c35b97802205379758b11b869ede2f5ab13a738493a93571268d66b2a875ae148625bd20578012103501e454bf00751f24b1b489aa925215d66af2234e3891c3b21a52bedb3cd711cffffffff01e8030000000000001976a914bef5a2f9a56a94aab12459f72ad9cf8cf19c7bbe88ac00000000")
assert(signedTx.vbytes == legacyInputBytes - 1)