LibWally Swift

Opinionated Swift wrapper around LibWally, a collection of useful primitives for cryptocurrency wallets.

Supports a minimal set of features based on v0.7.7. See also original docs.

• Core Functions
  • base58 encode / decode
• Crypto Functions
  • sign ECDSA, convert to DER
• Address Functions
  • Parse to scriptPubKey
  • Generate from scriptPubKey #7 (wishlist, done for SegWit)
  • Derive
  • WIF
  • Detect bech32 typos #4 (wishlist)
• BIP32 Functions
  • Derive scriptPubKey #6 (wishlist)
• BIP38 Functions
• BIP39 Functions
• Script Functions
  • Serialize scriptPubKey
  • Determine scriptPubkey type
• PSBT functions
  • Parse and serialize (base64 / binary)
  • Check completeness and extract transaction
• Transaction Functions
  • Compose and sign transaction
  • Calculate fee

Items marked with wishlist are not (yet) available upstream.

Multisig as well as Elements specific functions such as confidential addresses are not implemented.

Works with iOs 11+ on 64-bit devices and the simulator.

Usage

Derive address from a seed:

let mnemonic = BIP39Mnemonic("abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon about")
let masterKey = HDKey(mnemonic.seedHex("bip39 passphrase"))!
masterKey.fingerprint.hexString
let path = BIP32Path("m/44'/0'/0'")!
let account = try! masterKey.derive(path)
account.xpub
account.address(.payToWitnessPubKeyHash)

Derive address from an xpub:

let account = HDKey("xpub6ASuArnXKPbfEwhqN6e3mwBcDTgzisQN1wXN9BJcM47sSikHjJf3UFHKkNAWbWMiGj7Wf5uMash7SyYq527Hqck2AxYysAA7xmALppuCkwQ")
let receivePath = BIP32Path("0/0")!
key = account.derive(receivePath)
key.address(.payToPubKeyHash) # => 1JQheacLPdM5ySCkrZkV66G2ApAXe1mqLj

Parse an address:

var address = Address("bc1q6zwjfmhdl4pvhvfpv8pchvtanlar8hrhqdyv0t")
address?.scriptPubKey # => 0014d09d24eeedfd42cbb12161c38bb17d9ffa33dc77
address?.scriptPubKey.type # => .payToWitnessPubKeyHash

Create and sign a transaction:

let txId = "400b52dab0a2bb5ce5fdf5405a965394b43a171828cd65d35ffe1eaa0a79a5c4"
let vout: UInt32 = 1
let amount: Satoshi = 10000
let witness = Witness(.payToWitnessPubKeyHash(key.pubKey))
let input = TxInput(Transaction(txId)!, vout, amount, nil, witness, scriptPubKey)!
transaction = Transaction([input], [TxOutput(destinationAddress.scriptPubKey, amount - 110)])
transaction.feeRate // Satoshi per byte
let accountPriv = HDKey("xpriv...")
let privKey = try! accountPriv.derive(BIP32Path("0/0")!)
transaction.sign([privKey])
transaction.description # transaction hex

See also the included Playground and tests.

Install

Via CocoaPods:

pod 'LibWally', :git => 'https://github.com/blockchain/LibWally-Swift.git', :branch => 'master', :submodules => true

pod install --verbose

Build

Install dependencies:

brew install gnu-sed

Clone the repository, including submodules:

git clone https://github.com/blockchain/libwally-swift.git --recurse-submodules

Build libwally-core:

./build-libwally.sh -dsc