How to include my base64 signature to spend a UTXO

+1 vote
I'm trying to use the bitcoinjs-lib to spend an UTXO. I have a signature from the prior transaction that is in base64 format. I have the following standard transaction builder as a starting base:

var bitcoin = require(‘bitcoinjs-lib’);
var key = bitcoin.ECKey.fromWIF("put data here");
var tx = new bitcoin.TransactionBuilder();
tx.addInput("txid here", 1);
tx.addOutput("receiver addr here", 345000);
tx.sign(0, key);
console.log(tx.build().toHex());

var key = Bitcoin.ECKey.fromWIF(‘private key’);
var tx=Bitcoin.Transaction.fromHex(‘HEX-data from step 1’);
tx.sign(0, key);
tx.toHex(); // HEX-data of signed transaction

All of these standard transaction builders like the above no matter what the programming language insist on using a WIF key format. But I need to use a base64 signature that I have already to build the transaction. I'm participating in a challenge and apparently that is the challenge  --- to figure out how to spend the UTXO using a base64 signature that was provided participants. Can someone help me with this?
asked Oct 5 by Writer007
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