Error creating a transaction with Cardano Serialization Library

Question

I am trying to create a transaction using the Cardano Serialization Library but I cannot figure out what is going wrong. The code is

const BlockFrost = require('@blockfrost/blockfrost-js');
const {
PrivateKey, Vkey, Ed25519Signature, PublicKey, Vkeywitnesses , TransactionHash
  TransactionBuilderConfigBuilder,
  LinearFee,
  BigNum,
  TransactionBuilder,
  Transaction,
  TransactionWitnessSet,
  hash_transaction,
  make_vkey_witness,
  Address,
  Value,
  TransactionOutput,
  TransactionInput,
} = require('@emurgo/cardano-serialization-lib-nodejs');

const BLOCKFROST_API_KEY = 'xxxxx';
const PRIVATE_KEY =
  PrivateKey.from_bech32('ed25519e_sk14p2a82zpk7y27pme7sy8yxaw0ad93j47k7dvgnc55e50lfm66a88rmz0zh0ezfqd7x30mclsjaqtkzmazy2l6crfxxd0j9ynmzxn6ac6vryrz');

const RECEIVER_ADDRESS = Address.from_bech32(
  'addr_test1qpzqmyejxwvwal9vx6w0wgezvpmjlp3cqwfg2vkjt0y9fns0d5cyvvu88y78wtfl8xyey3gr3ygpxpphevvmz7ulaf2qrhxz34',
);

const SEND_AMOUNT = '5000000';

const API = new BlockFrost.BlockFrostAPI({
  projectId: BLOCKFROST_API_KEY,
  isTestnet: true,
});

const _transactionConfig = async () => {
  const epoch = (await API.epochsLatest()).epoch;
  return await API.epochsParameters(epoch);
};

const _configureTransactionBuilder = async () => {
  // const protocolParams = await _transactionConfig();
  try {
    return (
      TransactionBuilderConfigBuilder.new()
        .fee_algo(
          LinearFee.new(BigNum.from_str('44'), BigNum.from_str('155381')),
        )
        .pool_deposit(BigNum.from_str('500000000'))
        .key_deposit(BigNum.from_str('2000000'))
        .max_tx_size(16384)
        .max_value_size(5000)
        .coins_per_utxo_word(BigNum.from_str('34482'))
        .prefer_pure_change(true)
        .build()
    );
  } catch (error) {
    console.log(`Error in tx config: ${error}`);
  }
};

const buildTransaction = async () => {
  try {
    const txBuilderConfiguration = await _configureTransactionBuilder();
    const txBuilder = TransactionBuilder.new(txBuilderConfiguration);

    //add key hash input
    txBuilder.add_key_input(
      PRIVATE_KEY.to_public().hash(),
      TransactionInput.new(
        TransactionHash.from_bytes(
          Buffer.from('d56839c08b51e159a3931b36c65b1305aa82e8625a0b2d6969f200b3ddf806cf', 'hex'), //tx hash on ada received from faucet
          0, //index
        ),
      ),
      Value.new(BigNum.from_str(SEND_AMOUNT))
    )

    //tx outputs
    const txOutputs = TransactionOutput.new(
      RECEIVER_ADDRESS,
      Value.new(BigNum.from_str(SEND_AMOUNT)),
    );
    txBuilder.add_output(txOutputs);

    //latest block
    const latestBlock = await API.blocksLatest();
    const currentSlot = latestBlock.slot;
    txBuilder.set_ttl(currentSlot + 7200); //+2h from current slot

    //metadata
    // txBuilder.add_json_metadatum(BigNum.from_str('0'), 'today is a great day');

    txBuilder.set_fee(BigNum.from_str("190000"));
    // txBuilder.add_change_if_needed(SENDER_ADDRESS);
    //build tx
    const txBody = txBuilder.build();

    //make witness
    const txHash = hash_transaction(txBody);
    
    const witnesses= TransactionWitnessSet.new();
    const vKeyWitness = Vkeywitnesses.new();

    vKeyWitness.add(make_vkey_witness(txHash, PRIVATE_KEY));
    witnesses.set_vkeys(vKeyWitness);

    const signedTx = Transaction.new(txBody, witnesses);

    const response = API.txSubmit(signedTx.to_bytes());


    return response;
  } catch (error) {
    console.log(`Tx compose error: ${error}\n`);
    console.error(error.stack);
  }
};

module.exports = {
  buildTransaction,
};

I am getting the error below. From my research it apparently means I am not using the correct keys for the witness. But I can't find a way to fix it. Any ideas on what could be wrong?

BlockfrostServerError: "transaction submit error ShelleyTxValidationError ShelleyBasedEraAlonzo (ApplyTxError [UtxowFailure (WrappedShelleyEraFailure (MissingVKeyWitnessesUTXOW (WitHashes (fromList [KeyHash \"0c7a0e8dc785e893f8fca246646ba10df9d5bdd5ebed92e72b163e75\"])))),UtxowFailure (WrappedShelleyEraFailure (UtxoFailure (ValueNotConservedUTxO (Value 1000000000 (fromList [])) (Value 5190000 (fromList [])))))])"

Answer 1

ValueNotConservedUTxO (Value 1000000000 (fromList [])) (Value 5190000 (fromList []))

This suggests that your sum of inputs (1000000000) do not match the sum of outputs (5190000), you'd want to send the delta (i.e. input - (output + fees) ), i.e. change back to your original address.