Bitcoin and Bitcoin Cash(ABC) SPV wallet toolkit implemented in Kotlin. This is a full implementation of SPV node including wallet creation/restore, syncronzation with network, send/receive transactions, and more.

• Full SPV implementation for fast mobile performance
• Send/Receive Legacy transactions (P2PKH, P2PK, P2SH)
• Send/Receive Segwit transactions (P2WPKH)
• Send/Receive Segwit transactions compatible with legacy wallets (P2WPKH-SH)
• Fee calculation depending on wether sender pays the fee or receiver
• Encoding/Decoding of base58, bech32, cashaddr addresses
• BIP32 hierarchical deterministic wallets implementation.
• BIP39 mnemonic code for generating deterministic keys.
• BIP44 multi-account hierarchy for deterministic wallets.
• BIP21 URI schemes, which include payment address, amount, label and other params
• Real-time fee rates

BitcoinKit requires you to provide mnemonic phrase when it is initialized:

val words = listOf("skill", ..., "century")

val context: Context = App.instance
val walletId = 'MyWalletId'
val bitcoinKit = BitcoinKit(context, walletId, words, BitcoinKit.NetworkType.MainNet)

val bitCashKit = BitcoinCashKit(context, walletId, words, BitcoinCashKit.NetworkType.MainNet)

Both networks can be configured to work in MainNet or TestNet

• peerSize: Can be configured for number of peers to be connected (default: 10)
• confirmationsThreshold: Minimum number of confirmations required for an unspent output in incoming transaction to be spent (default: 6)

BitcoinKit requires to be started with start command, but does not need to be stopped. It will be in synced state as long as it is possible:

bitcoinKit.start()

BitcoinKit uses internal database for storing data fetched from blockchain. The clear command can be used to stop and clean all stored data:

bitcoinKit.clear()

BitcoinKit holds all kinds of data obtained from and needed for working with blockchain network

Balance is provided in Satoshi:

bitcoinKit.balance
// 2937096768

Get an address which you can receive coins to. Receive address is changed each time after you actually get a transaction in which you receive coins to that address

bitcoinKit.receiveAddress()
// mfu3iYeZuh18uuN4CrGYz34HSMynZBgZyg

You can get all your transactions as follows:

bitcoinKit.transactions

TransactionInfo(
    transactionHash=baede6420b4b2869cba87d768a7b4e2eef2a9899149f24c5c3d3ff66b8ad1405,
    from=[TransactionAddress(address=my1ysPMHdeQD6kwnimipbvFrr5NRHDvNgz, mine=false)],
    to=[
        TransactionAddress(address=moyrWfrks5EsHLb2hqUr8nUnC9q9DYXMtK, mine=true),
        TransactionAddress(address=2NDk1BuuKnbVqDAMVgGr6xurnctfaQVxFoN, mine=false)
    ],
    amount=32500000,
    blockHeight=1316822,
    timestamp=1527595501
  ),
  TransactionInfo(
    transactionHash=60ff9d204c17e0e71a1fd2d3f60b1bada5573857691d30d7518311057cc75720, 
    from=[
        TransactionAddress(address=mtmnfGuW4e5RbC64r3vx2qFhS3pobf57Ty, mine=false)
    ], 
    to=[
        TransactionAddress(address=mt59yxihUxy117RPQuEVQ7QSRuHJnRT4fG, mine=true), 
        TransactionAddress(address=2NAn7FBKvMFWteiHKSDDBudUP4vPwiBfVkr, mine=false)
    ], 
    amount=16250000, 
    blockHeight=1316823, 
    timestamp=1527595771
)
...

In order to create new transaction, call send(address: String, value: Int, senderPay: Boolean = true) method on BitcoinKit

• senderPay: parameter defines who pays the fee

bitcoinKit.send("mrjQyzbX9SiJxRC2mQhT4LvxFEmt9KEeRY", 1000000)

This function first validates a given address and amount, creates new transaction, then sends it over the peers network. If there's any error with given address/amount or network, it raises an exception.

One can validate address and fee by using following methods:

bitcoinKit.validate(address = "mrjQyzbX9SiJxRC2mQhT4LvxFEmt9KEeRY")
bitcoinKit.fee(value = 1000000, address = "mrjQyzbX9SiJxRC2mQhT4LvxFEmt9KEeRY", senderPay: true)

• senderPay: parameter defines who pays the fee

You can use parsePaymentAddress method to parse a BIP21 URI:

bitcoinKit.parsePaymentAddress("bitcoin:175tWpb8K1S7NmH4Zx6rewF9WQrcZv245W?amount=50&label=Luke-Jr&message=Donation%20for%20project%20xyz")

BitcoinPaymentData(
  address=175tWpb8K1S7NmH4Zx6rewF9WQrcZv245W, 
  version=null, 
  amount=50.0,
  label=Luke-Jr,
  message=Donation for project xyz,
  parameters=null
)

BitcoinKit provides with data like transactions, blocks, balance, kitState in real-time. BitcoinKit.Listener interface must be implemented and set to BitcoinKit instance to receive that data.

class MainViewModel : ViewModel(), BitcoinKit.Listener {

    private var bitcoinKit: BitcoinKit
    ...
    
    init {
        bitcoinKit = BitcoinKit(words, BitcoinKit.NetworkType.TestNet)
        bitcoinKit.listener = this
    }
    
    override fun onTransactionsUpdate(bitcoinKit: BitcoinKit, inserted: List<TransactionInfo>, updated: List<TransactionInfo>) {
        // do something with transactions
    }

    override fun onTransactionsDelete(hashes: List<String>) {
        // do something with transactions
    }

    override fun onBalanceUpdate(bitcoinKit: BitcoinKit, balance: Long) {
        // do something with balance
    }

    override fun onLastBlockInfoUpdate(bitcoinKit: BitcoinKit, blockInfo: BlockInfo) {
        // do something with blockInfo
    }

    override fun onKitStateUpdate(bitcoinKit: BitcoinKit, state: KitState) {
        // These states can be used to implement progress bar, etc
        when (state) {
            is KitState.Synced -> {

            }
            is KitState.Syncing -> {
                // val progress: Double = state.progress
            }
            is KitState.NotSynced -> {
                
            }
        }
    }
}

Listener events are run in a dedicated background thread. It can be switched to main thread by setting the listenerExecutor property to MainThreadExecutor()

bitcoinKit.listenerExecutor = MainThreadExecutor()

• JDK >= 1.8
• Android 6 (minSdkVersion 23) or greater

Add the JitPack to module build.gradle

repositories {
    maven { url 'https://jitpack.io' }
}

Add the following dependency to your build.gradle file:

dependencies {
    implementation 'com.github.horizontalsystems:bitcoin-kit-android:master-SNAPSHOT'
}

All features of the library are used in example project. It can be referred as a starting point for usage of the library.

• Example App

• HDWalletKit - HD Wallet related features, mnemonic phrase

Contributing

The BitcoinKit is open source and available under the terms of the MIT License