Expected private key to be an Uint8Array with length 32

Question

i am trying to send a transaction but it throws an error. still i am not sending any transaction just signing it...

Error: Expected private key to be an Uint8Array with length 32 at assert (C:\web3\node_modules\secp256k1\lib\index.js:18:20) at isUint8Array (C:\web3\node_modules\secp256k1\lib\index.js:31:7) at Object.ecdsaSign (C:\web3\node_modules\secp256k1\lib\index.js:254:7) at Object.exports.sign (C:\web3\node_modules\ethereumjs-util\dist\secp256k1v3-adapter.js:247:25) at Object.exports.ecsign (C:\web3\node_modules\ethereumjs-util\dist\signature.js:12:25) at Transaction.sign (C:\web3\node_modules\ethereumjs-tx\dist\transaction.js:230:37) at Object.callback (C:\web3\transaction1.js:28:8) at sendTxCallback (C:\web3\node_modules\web3-core-method\lib\index.js:533:29) at C:\web3\node_modules\web3-core-requestmanager\lib\index.js:308:9 at XMLHttpRequest.request.onreadystatechange (C:\web3\node_modules\web3-providers-http\lib\index.js:98:13) at XMLHttpRequestEventTarget.dispatchEvent (C:\web3\node_modules\xhr2-cookies\dist\xml-http-request-event-target.js:34:22) at XMLHttpRequest._setReadyState (C:\web3\node_modules\xhr2-cookies\dist\xml-http-request.js:208:14) at XMLHttpRequest._onHttpResponseEnd (C:\web3\node_modules\xhr2-cookies\dist\xml-http-request.js:318:14) at IncomingMessage. (C:\web3\node_modules\xhr2-cookies\dist\xml-http-request.js:289:61) at IncomingMessage.emit (events.js:327:22) at endReadableNT (internal/streams/readable.js:1327:12)

var Tx = require('ethereumjs-tx')

const Web3 = require('web3')
const web3 = new Web3('http://127.0.0.1:7545')

const account1 = '0x67d30ef950015Ab1a03e30ED5d5F2A26de196C4d'
const account2 = '0x04bCD71C67656cFda695F14a9E9Bf8B6064b8AD1'

const privateKey1 = 'c429601ee7a6167356f15baa70fd8fe17b0325dab7047a658a31039e5384bffd'
const privateKey2 = '60495127495614d5aadb1f4561a3989d6636cbe55ada58c685ef28cff01bde21'

const privateKey1Buffer = Buffer.from(privateKey1, 'hex')
const privateKey2Buffer = Buffer.from(privateKey2, 'hex')

console.log('Buffer 1: ', privateKey1Buffer)
console.log('Buffer 2: ', privateKey2Buffer)

web3.eth.getTransactionCount(account1, (err, txCount) => {
    const txObject = {
      nonce:    web3.utils.toHex(txCount),
      to:       account2,
      value:    web3.utils.toHex(web3.utils.toWei('0.1', 'ether')),
      gasLimit: web3.utils.toHex(21000),
      gasPrice: web3.utils.toHex(web3.utils.toWei('10', 'gwei'))
    }

    const tx = new Tx.Transaction(txObject)
    tx.sign(privateKey1)

    const serializedTx = tx.serialize().toString('hex')
    // const raw = '0x' + serializedTx.toString('hex')

    console.log('tx :', tx)
    console.log('serializedTx :', serializedTx)
    console.log('raw :', raw)
  })

Answer 1

This part was wrong.

tx.sign(privateKey1)

Fix it like this:

tx.sign(privateKey1Buffer)

Answer 2

I had this error because I hadn't removed 0x from the prefix of the private key.