Bitcoin Message Signer

by #sathoshiengineeringcrew

A dart library to sign messages like Bitcoin core.

How to use

Add the dependency: dart pub add bitcoin_message_signer or flutter pub add bitcoin_message_signer

Use it to sign messages with a bech32 script (bc1... address):

import 'package:bitcoin_message_signer/bitcoin_message_signer.dart';

/// ...

final signer = BitcoinMessageSigner(
  privateKey: Uint8List.fromList(privateKey),
  scriptType: P2WPKH(),
);
final signature = signer.signMessage(message: 'Hello Bitcoin-World!');

Supported script types

• P2PKH uncompressed: 1... address from an uncompressed private key (5...)
• P2PKH compressed: 1... address from a compressed private key (L... or K...)
• P2SH: 3... addresses
• P2WPKH: bc1... addresses

Checkout examples in the tests.

Where do I get the private key from?

This depends on the bitcoin library you use:

• bdk_flutter returns the private key as List<int>, therefore you can simply transform it using Uint8List.fromList(privateKey).
• Most other libraries probably return the private key either as list too, as hex string or in WIF format.
• If the private key is in WIF format, you probably need another library to transform the private key into a Uint8List. You just have to find a library.

Tip

Testing a private key in (bitcoin) WIF format: You will need to use a conversion tool, e.g. you can use a converter like the one found at https://privatekeys.pw/calc for testing these keys (WIF --> Priv). Additionally, a simple Google search for "bitcoin WIF to HEX" will provide multiple tool options.

Verify the signature

https://www.verifybitcoinmessage.com/

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