Introduction

Overview

TwoStack WalletSDK is a Bitcoin library for the Dart Language ( dartlang.org ), loosely based on the Moneybutton/BSV Javascript library. This library has been built in line with the ideals espoused by BitcoinSV, i.e. massive on-chain scaling, protocol stability and original-bitcoin-protocol implementation. It is intended for use in building multi-platform applications using the Flutter framework, or server-side bitcoin applications using frameworks like Serverpod

A note about Version 2.x (August 2023)

Version 2.x of the library is a major refactor and breaks backwards compatibility with several previous library APIs.

• A new TransactionBuilder class for composing Transactions
• Removal of the old Builder interface which was directly attached to the Transaction class
• A complete re-implementation of the Script Interpreter
• The Sighash class now exposes the SigHash Pre-Image; useful when creating OP_PUSH_TX spending scripts.
• A new ScriptBuilder class to make it easy to create custom locking/unlocking scripts.
• Merged contributed code to have better Flutter Web support.

Generally Supported features are :

• Custom-Script Builder Interface to support novel locking/spending conditions within Script
• Pre-built library code to support "standard" locking/unlocking scripts
  • P2PKH Transactions
  • P2SH Transactions
  • P2MS Transactions (naked multisig)
  • P2PK Transactions
  • Data-only Transactions (locked with OP_FALSE OP_RETURN)
  • Spendable data-carrier Transactions (locked with PUSH_DATA [your_data] OP_DROP [P2PKH locking code])
• HD Key Derivation (BIP32)
• Original Bitcoin Address format
• Bitcoin Signed Messages
• Mnemonic Seed Support (BIP39)
• A built-in Bitcoin Script Interpreter
• ECIES Encryption / Decryption (Supports Electrum ECIES / BIE1 )

Sample of the Transaction API:

    var utxo = txWithUTXO.outputs[0]; 
    var outpoint = TransactionOutpoint(txWithUTXO.id, 0, utxo.satoshis, utxo.script);
    var signer = TransactionSigner(SighashType.SIGHASH_FORKID.value | SighashType.SIGHASH_ALL.value, privateKey);

    var unlocker = P2PKHUnlockBuilder(privateKey.publicKey);
    
    var transaction = TransactionBuilder()
        .spendFromOutpointWithSigner(signer, outpoint, TransactionInput.MAX_SEQ_NUMBER, unlocker)
        .spendToPKH(recipientAddress, BigInt.from(50000000)) //spend half of a bitcoin 
        .sendChangeToPKH(changeAddress) // spend change to a different address
        .withFeePerKb(50) //set a fee of 50 satoshis per kilobyte
        .build(false); //build the transaction, disabling checks

    //at this point you have a fully signed transaction ready to be broadcast

    try {
      transaction.verify(); //perform a pre-broadcast sanity check on the transaction
    } on VerificationException catch (ex){
      print("Transaction failed verification - ${ex.cause}");  
    }

Installation

This library was built using version 3.0.7 of the Dart SDK( https://dart.dev/tools/sdk ).
As of Version 1.0.0 this library supports Dart Null Safety. Current minimum Dart SDK version required is version 2.17.0.

Navigate to the root folder of this project, and pull the required supported Dart libraries using the pub package manager.

> pub get

Running the Tests

In the root folder of this project, run the command:

> pub run test

Acknowledgement

A debt of gratitude is owed to the developers acknowledged in the LICENSE file. Without the hard work of individuals working on earlier library and node implementations like Bitcoin Core, Bitcoin Cash, MoneyButton/BSV, BitcoinJ and many more, this library would likely not have come to fruition. Thank you.

Contact

You can reach the author at :

• @twostack_org on Twitter
• [email protected] (PayMail to buy me a beer)
• [email protected] (drop me an email. GPG supported. )