Go Ethereum – How to Create and Sign a Transaction Locally Using Go

go-ethereumjson-rpc

Geth's code can be used as a library. Are there any code examples that use Geth to sign a transaction locally? I then want to POST the resulting string using eth_sendRawTransaction.

Best Answer

Richard's answer pointed me in the right direction, but I had to remove some cruft to get it to do what I wanted. Here's some code that works (just replace the hardcoded values):

package main

import (
    "bytes"
    "fmt"
    "math/big"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/core/types"
    "github.com/ethereum/go-ethereum/crypto"
)

func main() {

    chainId := big.NewInt(3) // ropsten

    senderPrivKey, _ := crypto.HexToECDSA("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa")
    recipientAddr := common.HexToAddress("0xbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb")

    nonce := uint64(7)
    amount := big.NewInt(1000000000000000000) // 1 ether
    gasLimit := big.NewInt(100000)
    gasPrice := big.NewInt(20000000000) // 20 gwei

    tx := types.NewTransaction(nonce, recipientAddr, amount, gasLimit, gasPrice, nil)

    signer := types.NewEIP155Signer(chainId)
    signedTx, _ := types.SignTx(tx, signer, senderPrivKey)
    fmt.Println(signedTx)

    var buff bytes.Buffer
    signedTx.EncodeRLP(&buff)
    fmt.Printf("0x%x\n", buff.Bytes())
}

Related Solutions

Ethereum Transactions – Creating and Signing Offline Raw Transactions

ethereumjs-tx is a library with this example:

npm install ethereumjs-tx

const Tx = require('ethereumjs-tx').Transaction
var privateKey = new Buffer('e331b6d69882b4cb4ea581d88e0b604039a3de5967688d3dcffdd2270c0fd109', 'hex')

var rawTx = {
  nonce: '0x00',
  gasPrice: '0x09184e72a000', 
  gasLimit: '0x2710',
  to: '0x0000000000000000000000000000000000000000', 
  value: '0x00', 
  data: '0x7f7465737432000000000000000000000000000000000000000000000000000000600057'
}

var tx = new Tx(rawTx)
tx.sign(privateKey)

var serializedTx = tx.serialize()
console.log(serializedTx.toString('hex'))

C# Transaction – How to Sign a Transaction Using C#

To expand the other response, to provide offline transaction signing in Nethereum you can do the following:

First, you will need your private key, and sender address. You can retrieve the sender address from your private key using Nethereum.Core.Signing.Crypto.EthECKey.GetPublicAddress(privateKey); if you only have the private key.

var privateKey = "0xb5b1870957d373ef0eeffecc6e4812c0fd08f554b37b233526acc331bf1544f7"; var senderAddress = "0x12890d2cce102216644c59daE5baed380d84830c";

Now using web3 first you will need to retrieve the total number of transactions of your sender address.

var web3 = new Web3(); var txCount = await web3.Eth.Transactions.GetTransactionCount.SendRequestAsync(senderAddress);

The txCount will be used as the nonce to sign the transaction.

Now using web3 again, you can build an encoded transaction as following:

var encoded = web3.OfflineTransactionSigning.SignTransaction(privateKey, receiveAddress, 10, txCount.Value);

If you need to include the data and gas there are overloads for it.

You can verify an encoded transaction: Assert.True(web3.OfflineTransactionSigning.VerifyTransaction(encoded));

Or get the sender address from an encoded transaction:

web3.OfflineTransactionSigning.GetSenderAddress(encoded);

To send the encoded transaction you will "SendRawTransaction"

var txId = await web3.Eth.Transactions.SendRawTransaction.SendRequestAsync("0x" + encoded);

You can see this example on the unit test

Or a "real" implementation on the Game sample

Best Answer

Related Solutions

Ethereum Transactions – Creating and Signing Offline Raw Transactions

C# Transaction – How to Sign a Transaction Using C#

Related Topic