P2PK

P2PK (Pay-to-Public-Key) locks an Output to a Public Key itself, rather than to its hash: <pubkey> OP_CHECKSIG. Spending it takes only a Signature. It appears in early coinbase Outputs, and in some protocols.

The examples use the keys and the fundingTransaction helper described in About the examples.

Locking

final locker = P2PKLockBuilder(aliceKey.publicKey);
locker.getScriptPubkey().toString(type: 'asm'); // <33-byte public key> OP_CHECKSIG

Spending

P2PKUnlockBuilder does not work for spending

In 3.1.2, P2PKUnlockBuilder writes <signature> <public key>, which is the P2PKH shape. The Locking Script then checks the Signature against the wrong stack item, and the spend fails. Use a Signature-only unlocker until this is fixed.

A Signature-only Unlocking Script builder takes only a few lines (writing your own builders is covered in Custom script builders):

/// Unlocking Script for P2PK: the Signature alone.
class SignatureOnlyUnlocker extends UnlockingScriptBuilder {
  @override
  SVScript getScriptSig() {
    if (signatures.isEmpty) return SVScript(); // not signed yet
    return ScriptBuilder()
        .addData(Uint8List.fromList(HEX.decode(signatures[0].toTxFormat())))
        .build();
  }

  @override
  void parse(SVScript script) {}
}

We use it like any other unlocker:

final signer = DefaultTransactionSigner(sighashAll, aliceKey);

final tx = TransactionBuilder()
    .spendFromTxnWithSigner(signer, fundingTx, 0, TransactionInput.MAX_SEQ_NUMBER, SignatureOnlyUnlocker())
    .spendToPKH(aliceKey.toAddress(networkType: NetworkType.TEST), BigInt.from(9000))
    .build(false);