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Transaction format and fee rate

Fee rate

The current standard fee rate which applies to all transactions submitted to any of the TAAL transaction processing APIs is: 1 sat/kb
The minimum fee for any transaction is 1 sat.
The fee required is rounded depending on size of the transaction. The following list exemplifies the logic:
  • Transactions with 1.4999... kb > size > 0.0 kb => min absolute fee required = 1 sat.
  • Transactions with 2.4999... kb > size > 1.5 kb => min absolute fee required = 2 sat
  • Transactions with 3.4999... kb > size > 2.5 kb => min absolute fee required = 3 sat
  • ...

Transaction format

The format of transaction is bound to the standard of BSV transactions as described here.
There is a number of libraries which allow to build BSV transactions. Here is a short list:

Javascript example using version 1 of bsv.js and request modules

  1. 1.
    Create a new Node.js project:
    mkdir example
    cd example
    npm init -y
    npm install bsv@1
    npm install request
  2. 2.
    Save the following code to a main.js in your example folder:
    const fs = require('fs')
    const bsv = require('bsv')
    // Random key produced each time...
    const newKey = bsv.PrivateKey()
    console.log(`Private key: ${newKey.toString()}`)
    console.log(`Mainnet address: ${newKey.toAddress('mainnet').toString()}`)
    console.log(`
    1. Create a funding transaction by sending 1000 satoshis (0.00001 BSV) to ${newKey.toAddress('mainnet').toString()}.
    2. Add your Taal apiKey, and funding transaction txid and vout to 'generated.js'.
    3. Execute the generated code:
    node generated.js
    `)
    fs.writeFileSync('generated.js', `
    const bsv = require('bsv')
    var request = require('request')
    const privKey = bsv.PrivateKey('${newKey}')
    const apiKey = "" // Add Taal mainnet API Key
    const fundingTxid = "" // Add the funding transaction txid
    const fundingVout = -1 // Replace with funding transaction vout
    const returnAddress = "" // The address to return the 1000 satoshis (less fees)
    if (apiKey === "" || fundingTxid === "" || fundingVout === -1 || returnAddress === "") {
    console.log('This generated file needs an apiKey, a fundingTxid, a fundingVout and a returnAddress')
    process.exit(1)
    }
    const utxo1 = {
    txId: fundingTxid,
    outputIndex: fundingVout,
    address: privKey.toAddress('mainnet').toString(),
    script: bsv.Script.buildPublicKeyHashOut(privKey.publicKey).toHex(),
    satoshis: 1000
    }
    const tx1 = bsv.Transaction()
    .from(utxo1)
    .to(privKey.toAddress('mainnet').toString(), 800)
    .change(returnAddress)
    .sign(privKey)
    const utxo2 = {
    txId: tx1.hash,
    outputIndex: 0,
    address: privKey.toAddress('mainnet').toString(),
    script: bsv.Script.buildPublicKeyHashOut(privKey.publicKey).toHex(),
    satoshis: 800
    }
    const tx2 = bsv.Transaction()
    .from(utxo2)
    .change(returnAddress)
    .sign(privKey)
    const txBuffer = Buffer.concat([
    tx1.toBuffer(),
    tx2.toBuffer()
    ])
    // Send the transaction to Taal API...
    request.post({
    url: 'https://api.taal.com/api/v1/batchBroadcast',
    headers: {
    'Authorization': apiKey,
    'Content-Type': 'application/octet-stream'
    },
    body: txBuffer
    }, function(error, response, body) {
    console.log(error, response.statusCode, body)
    })
    `)
  3. 3.
    Execute the code and follow the onscreen instructions:
    node main.js