[Ethereum] chainID? Raw transaction from theEther wallet

myetherwalletraw-transactiontransactions

So I just ran a function from a contract on Ropsten from myetherwallet.com. It ran fine via metamask, but I was just wondering what chainID was in the rawTx file?

{
 "nonce":"0x2e",
 "gasPrice":"0x04e3b29200",
 "gasLimit":"0x14b40f",
 "to":"0x8d3cbc2cba343b97f656428eafa857ee01bda53b",
 "value":"0x2386f26fc10000",
 "data":"0x412a5a6d",
 "chainId":3
}

Best Answer

The chainid was added about 1 year ago in order to prevent replay attacks across channels. This was due to the ETH / ETC fork, but also applies to testnet and alternate chains (like Expanse). Here you can find a list of well known chainId values.

You can read about the discussion surrounding replay protection & EIP-155 here: https://github.com/ethereum/eips/issues/155

Related Solutions

[Ethereum] Hash of the transaction VS Transaction Hash or Transaction ID

The transaction ID calculation is correct. For the signing, the arguments are still RLP encoded (the dummy "v" for EIP-155 is a bit special, see below).

Take this live transaction as an example. It has the following parameters.

nonce = 0 [RLP: 0x80]
gasPrice = 50000000000 wei (0x0BA43B7400) [RLP: 85 0BA43B7400]
gasLimit = 21000 (0x5208) [RLP: 82 5208]
to = 0x7917bc33eea648809c285607579c9919fb864f8f [RLP: 94 7917bc33eea648809c285607579c9919fb864f8f]
value = 1050000000000000 wei (0x03BAF82D03A000) [RLP: 87 03BAF82D03A000]
data = <empty> [RLP: 80]
v = 018080 (this is a place-holder value before signing, see EIP-155)

Then the input parameters for the hash is the RLP of the concatenation:

EB80850BA43B7400825208947917bc33eea648809c285607579c9919fb864f8f8703BAF82D03A00080018080

And the hash value for the signing is:

python3
>>> from Crypto.Hash import keccak
>>> keccak_hash=keccak.new(digest_bits=256)
>>> txn=bytearray.fromhex('EB80850BA43B7400825208947917bc33eea648809c285607579c9919fb864f8f8703BAF82D03A00080018080')
>>> keccak_hash.update(bytes(txn))
<Crypto.Hash.keccak.Keccak_Hash object at 0x10fb6e2e8>
>>> print(keccak_hash.hexdigest())

which gives the result

a4060d01d4add248db470b4121616cbe5b2015daf328809000ec9a1d0954d649

For the transaction ID, do Keccak hash on the final raw transaction bytes (RLP encoded as you mentioned, which are also readable from Etherscan) and it will give the same result as shown on Etherscan.

Best Answer

Related Solutions

[Ethereum] Hash of the transaction VS Transaction Hash or Transaction ID

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