How can I simply sign an Ethereum transaction?

Question

I want to use blockcypher to work with the Ethereum network.

In the documentation they give an example of a signer tool written on Go, but I'm use Python.

What is the simplest way to sign a transaction?

I tried using web3.py, but I ran into some difficulties.

Here they give the following example:

transaction = {
       'to': '0xF0109fC8DF283027b6285cc889F5aA624EaC1F55',
       'value': 1000000000,
       'gas': 2000000,
       'gasPrice': 234567897654321,
       'nonce': 0,
       'chainId': 1
}
key = '0x4c0883a69102937d6231471b5dbb6204fe5129617082792ae468d01a3f362318'
signed = w3.eth.account.signTransaction(transaction, key)
signed.rawTransaction
HexBytes('0xf86a8086d55698372431831e848094f0109fc8df283027b6285cc889f5aa624eac1f55843b9aca008025a009ebb6ca057a0535d6186462bc0b465b561c94a295bdb0621fc19208ab149a9ca0440ffd775ce91a833ab410777204d5341a6f9fa91216a6f3ee2c051fea6a0428')
signed.hash
HexBytes('0xd8f64a42b57be0d565f385378db2f6bf324ce14a594afc05de90436e9ce01f60')
signed.r
4487286261793418179817841024889747115779324305375823110249149479905075174044
signed.s
30785525769477805655994251009256770582792548537338581640010273753578382951464
signed.v
37

But I do not understand some of the values that need to be passed to the transaction.

What is nonce, chainId?

Using such data:

transaction = {
    'to': '0xe980e77404ae62ab0f2d6b8510bd951e25185414',
    'value': value,
    'gas': 2000000,
    'gasPrice': 1000000000,,
    'nonce': 0,
    'chainId': 1
}

I get this error:

TypeError: Transaction had invalid fields: {'to': '0xe980e77404ae62ab0f2d6b8510bd951e25185414'}

Next, I tried to use ecdsa

But I was not able to find a simple example. I do not understand anything at all in cryptography, and I need the easiest way to send a transaction to the network without hammering through the details.

UPDATE

I tried to avoid using w3, since I only need to sign a transaction.

I was able to do this to create a signature:

import hashlib import binascii

import ecdsa

def sign(privkey, message):
    sk = ecdsa.SigningKey.from_string(
        binascii.unhexlify(privkey),
        curve=ecdsa.SECP256k1,
        hashfunc=hashlib.sha256
    )
    signature = binascii.hexlify(
        sk.sign(
            binascii.unhexlify(message),
            hashfunc=hashlib.sha256
        )
    )
    return signature

And the function works fine, I return a byte string like this:

b'4ace74a83082b5fc6d356083932b493e9fafbe0fabca19be3e77ccda188d08c6352f1fccb144e18b95a3f7e18f71fe95d79a9dd8ad9ecaa7490315f06a00177f'

But the length of this line is 128 characters, and in the example of the blockcypher a string of 148 characters.

After trying to send a signed transaction to the network, I receive such a reply:

{'error': 'Could not compute an address from provided signature: invalid transaction v, r, s values.'}

Most likely, I'm creating the wrong signature, but how to make the right one?

It seems I'm almost there, but still it's not working out.

Answer 1

Version 4.x of web3.py requires all addresses use a proper EIP 55 checksum. In my testing, I receive the same error as you until I convert the address to the correct checksummed form (note the capitalization):

0xe980E77404ae62aB0F2d6b8510BD951e25185414

(Note that you also have an extra comma that makes your code syntactically invalid, but I assume that's just a copy/paste error.)

Answer 2

Thanks @smarx for the hint.

However, I managed to find another solution:

from bitcoin import ecdsa_raw_sign
from bitcoin import der_encode_sig

def signing(transaction, privkey):
    signature = der_encode_sig(*ecdsa_raw_sign(transaction, privkey))
    return signature