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TutorialsLegacy TutorialsMulti-sig Transfer using Native Script

Multi-sig Transfer - Composable Functions

This tutorial shows how to claim fund from a multi-sig script address using the Composable Functions API.

Looking for the QuickTx version? Check the Multi-sig Transfer using Native Script tutorial for the recommended QuickTx approach.

Prerequisites

Before starting, make sure you have completed the setup steps from the main tutorial:

Claim fund from script address

Now we are ready to claim fund from the script address.

Define expected output

Let’s say we want to claim total 50 Ada from the script address and transfer 25 Ada to account1 and 25 Ada to account2.

String address1 = account1.baseAddress();
Output output1 = Output.builder()
        .address(address1)
        .assetName(LOVELACE)
        .qty(adaToLovelace(25))
        .build();
 
String address2 = account2.baseAddress();
Output output2 = Output.builder()
        .address(address2)
        .assetName(LOVELACE)
        .qty(adaToLovelace(25))
        .build();

Define Transaction

Line-1, Line-2 Create TxOutputBuilder from output1 and compose it with another TxOutputBuilder generated from output2.

Note: Check out various helper methods in com.bloxbean.cardano.client.function.helper.OutputBuilders to create TxOutputBuilder.

Line-3, Invoke TxOutputBuilder.buildInputs with a TxInputBuilder function. TxInputBuilder function builds required inputs based on the expected outputs.

As we are claiming fund from script address, both sender address and change address are set to scriptAddress in TxInputBuilder createFromSender method call.

Line-5, Add scriptAtLeast multi-sig script to transaction’s witnessset.

Line-7, Use BalanceTxBuilders.balanceTx composable function to balance the unbalanced transaction. It handles the followings to balance a transaction

  • Fee calculation
  • Adjust the outputs (if required)

The first parameter is change address which is set to scriptAddress as the fee is deducted from scriptAddress.

The second parameter is “no of signatures’. This is set to 2 as we have two signers for this transaction. This info is required to calculate correct fee as fee calculation depends on transaction size.

TxBuilder txBuilder = output1.outputBuilder()
                .and(output2.outputBuilder())
                .buildInputs(createFromSender(scriptAddress, scriptAddress))
                .andThen((context, txn) -> {
                    txn.getWitnessSet().getNativeScripts().add(scriptAtLeast);
                })
                .andThen(balanceTx(scriptAddress, 2));

Build and Sign

Line-1 & Line-2, Create UtxoSupplier & ProtocolParamsSupplier from the BackendService instance.

Line-4 & Line-5, Create TxSigner function by composing SignerProviders.signerFrom(Account... signers) & SignerProviders.signerFrom(SecretKey sk). Then use TxSigner to sign the transaction. In this case we are signing the transaction with account1 and secretkey (third key) as we need at least 2 signatures as per the rule defined in the multi-sig script.

Alternatively, you can also sign with account1 and account2.

Line-6, Initialize TxBuilderContext using UtxoSupplier and ProtocolParamsSupplier.

Using TxBuilderContext you can customize few behaviors during transaction building.

For example: Select a different UtxoSelectionStrategy implementation

UtxoSupplier utxoSupplier = new DefaultUtxoSupplier(backendService.getUtxoService());
ProtocolParamsSupplier protocolParamsSupplier = new DefaultProtocolParamsSupplier(backendService.getEpochService());
 
TxSigner signers = signerFrom(account1)
                .andThen(signerFrom(secretKey)); //3rd sk/vk pair
Transaction signedTransaction = TxBuilderContext.init(utxoSupplier, protocolParamsSupplier)
                .buildAndSign(txBuilder, signers);

Submit the transaction to Cardano network

Now we are ready to submit the transaction to the network. In this example, we are going to submit this transaction through BackendService. Alternatively, you can submit the generated transaction using your own TransactionProcessor implementation.

Result<String> result = backendService.getTransactionService().submitTransaction(signedTransaction.serialize());
System.out.println(result);

If successful, result.isSuccessful() will return true.

Now copy the transaction id from the output and then go to a Cardano explorer, Cardanoscan  or Cardano Explorer , to check the transaction details. You may need to wait for few secs to a min depending on the blockchain load.

Full Source Code

import com.bloxbean.cardano.client.account.Account;
import com.bloxbean.cardano.client.address.AddressProvider;
import com.bloxbean.cardano.client.api.ProtocolParamsSupplier;
import com.bloxbean.cardano.client.api.UtxoSupplier;
import com.bloxbean.cardano.client.api.model.Result;
import com.bloxbean.cardano.client.backend.api.BackendService;
import com.bloxbean.cardano.client.backend.api.DefaultProtocolParamsSupplier;
import com.bloxbean.cardano.client.backend.api.DefaultUtxoSupplier;
import com.bloxbean.cardano.client.backend.blockfrost.common.Constants;
import com.bloxbean.cardano.client.backend.blockfrost.service.BFBackendService;
import com.bloxbean.cardano.client.common.model.Networks;
import com.bloxbean.cardano.client.crypto.KeyGenUtil;
import com.bloxbean.cardano.client.crypto.SecretKey;
import com.bloxbean.cardano.client.crypto.VerificationKey;
import com.bloxbean.cardano.client.function.Output;
import com.bloxbean.cardano.client.function.TxBuilder;
import com.bloxbean.cardano.client.function.TxBuilderContext;
import com.bloxbean.cardano.client.function.TxSigner;
import com.bloxbean.cardano.client.transaction.spec.Transaction;
import com.bloxbean.cardano.client.transaction.spec.script.ScriptAtLeast;
import com.bloxbean.cardano.client.transaction.spec.script.ScriptPubkey;
 
import static com.bloxbean.cardano.client.common.ADAConversionUtil.adaToLovelace;
import static com.bloxbean.cardano.client.common.CardanoConstants.LOVELACE;
import static com.bloxbean.cardano.client.function.helper.BalanceTxBuilders.balanceTx;
import static com.bloxbean.cardano.client.function.helper.InputBuilders.createFromSender;
import static com.bloxbean.cardano.client.function.helper.SignerProviders.signerFrom;
 
public class MultiSigTransfer {
 
    public void transfer() throws Exception {
        //First account
        String account1Mnemonic = "turkey elder dad veteran they lumber feature garment race answer file erase riot resist sting process law deputy turtle foil legal calm exist civil";
        Account account1 = Account.createFromMnemonic(Networks.testnet(), account1Mnemonic);
 
        //Second account
        String account2Mnemonic = "report crowd trophy rough twin column access include evolve awkward world random bounce pave select rocket vote junk farm group main boat tissue mad";
        Account account2 = Account.createFromMnemonic(Networks.testnet(), account2Mnemonic);
 
        //Third account payment key
        String paymentSigningKeyCborHex = "58205d9ccc4202bde1785708c10f8b13231d5a57078c326d0e0ff172191f975a983e";
        SecretKey secretKey = new SecretKey(paymentSigningKeyCborHex);
        VerificationKey verificationKey = KeyGenUtil.getPublicKeyFromPrivateKey(secretKey);
 
        //Derive verification key for account1 and account2
        VerificationKey account1Vk = VerificationKey.create(account1.publicKeyBytes());
        VerificationKey account2Vk = VerificationKey.create(account2.publicKeyBytes());
 
        //Create native script with type=sig for each verification key
        ScriptPubkey scriptPubkey1 = ScriptPubkey.create(account1Vk);
        ScriptPubkey scriptPubkey2 = ScriptPubkey.create(account2Vk);
        ScriptPubkey scriptPubkey3 = ScriptPubkey.create(verificationKey);
 
        //Create multi-sig script with type "atLeast"
        ScriptAtLeast scriptAtLeast = new ScriptAtLeast(2)
                .addScript(scriptPubkey1)
                .addScript(scriptPubkey2)
                .addScript(scriptPubkey3);
 
        //addr_test1wr6fvn0y3rumu30ch3lrggss4vmgsr65cxly2t6dulvwamq3y98et
        String scriptAddress = AddressProvider.getEntAddress(scriptAtLeast, Networks.testnet()).toBech32();
 
        // For Blockfrost
        String bf_projectId = "preprod...";
        BackendService backendService = new BFBackendService(Constants.BLOCKFROST_PREPROD_URL, bf_projectId);
        // For Koios
        //BackendService backendService = new KoiosBackendService(Constants.KOIOS_PREVIEW_URL);
 
        //Define outputs
        String address1 = account1.baseAddress();
        Output output1 = Output.builder()
                .address(address1)
                .assetName(LOVELACE)
                .qty(adaToLovelace(25))
                .build();
 
        String address2 = account2.baseAddress();
        Output output2 = Output.builder()
                .address(address2)
                .assetName(LOVELACE)
                .qty(adaToLovelace(25))
                .build();
 
        TxBuilder txBuilder = output1.outputBuilder()
                .and(output2.outputBuilder())
                .buildInputs(createFromSender(scriptAddress, scriptAddress))
                .andThen((context, txn) -> {
                    txn.getWitnessSet().getNativeScripts().add(scriptAtLeast);
                })
                .andThen(balanceTx(scriptAddress, 2));
 
 
        UtxoSupplier utxoSupplier = new DefaultUtxoSupplier(backendService.getUtxoService());
        ProtocolParamsSupplier protocolParamsSupplier = new DefaultProtocolParamsSupplier(backendService.getEpochService());
 
        TxSigner signers = signerFrom(account1)
                .andThen(signerFrom(secretKey)); //3rd sk/vk pair
        Transaction signedTransaction = TxBuilderContext.init(utxoSupplier, protocolParamsSupplier)
                .buildAndSign(txBuilder, signers);
 
        Result<String> result = backendService.getTransactionService().submitTransaction(signedTransaction.serialize());
        System.out.println(result);
 
    }
 
    public static void main(String[] args) throws Exception {
        new MultiSigTransfer().transfer();
    }
}

What’s next ?

Update the multi-sig script to support time-lock. For example, evaluate to true if minimum 2 signatures and slot number is after X.

Hint: Use RequireTimeAfter with RequireMOf to create multi-sig script.

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