exonum/exonum

I'm doing this directly from Flutter/Dart using ProtocolBuffer, as Dart language is not fully supported as official client.

For example, the issue funds works as intended. I can reload, create wallet and all. Here's the code:

  /// Issue funds, or reload with the [amount] is the amount to be reloaded
  /// signed with the sender's [KeyPair]
  ///
  SignedMessage signIssueFunds(String amount, NaCl.KeyPair keyPair) {
    assert(amount.isNotEmpty);

    /// Prepare the [Issue] with [amount] and [seed]
    ///
    Issue issue = Issue()
      ..amount = Int64.parseInt(amount)
      ..seed = _getSeed();

    /// Return a signed message for [methodId], [arguments], and [KeyPair]
    ///
    return _signGeneratedMessage(TX_ISSUE_ID, issue.writeToBuffer(), keyPair);
  }

But the transfer didn't work as it says missing recipient key as mentioned above. The code below follows exactly the data needed in the ProtocolBuffer generated files. Otherwise, I cannot get the error response from Exonum node. Here's the gist of the code

  SignedMessage signTransferFunds(
      Uint8List to, String amount, NaCl.KeyPair keyPair) {
    assert(to.isNotEmpty);
    assert(amount.isNotEmpty);

    /// Prepare the [Transfer] with, [to], [amount], and [seed]
    ///
    Transfer transfer = Transfer()
      ..to = (Hash()..data = to)
      ..amount = Int64.parseInt(amount)
      ..seed = _getSeed();

    /// Return a signed message for [methodId], [arguments], and [KeyPair]
    ///
    return _signGeneratedMessage(
        TX_TRANSFER_ID, transfer.writeToBuffer(), keyPair);
  }

Anybody can point me to the right direction?
Thanks in advance.