Find the creator of a contract

Question

I want to prove that a contract was deployed by a specific address (a factory contract). I have noticed that block explorers such as https://etherscan.io/ list the contract creator. How do they get this information? I cant find any way of getting a contracts creators address from the the etherscan api.

How can I identify the address that deployed a contract?

Answer 1

If possible, save the users, transactions and contracts as you send them. This way you don't have to look for them later.

If that's not an option, the long route is to find all the transactions related to the contract address. The first incoming one should be the contract creation transaction, the sender of which is the creator.

Answer 2

If you understand how etherscan works you'll be able to do what you are asking.

See : How does Etherscan work?

What etherscan do is reverse of what you are trying to. ie you are trying to get the creator of a contract from an address. Etherscan index the entire blockchain and create relationships between blocks, transactions and accounts.

Etherscan see a block and index all the transactions first, then associate the creation of contracts with the accounts that sent the transactions.

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I presuming you are asking for a native geth/web3/etc method that would give you a contract creators address. If so I am not aware of any such method.

Answer 3

If you use Etherscan or some other third party blockchain scraper, then chances are the first transaction returned by their API will be the contract creation transaction. You'll be able to tell because the first transaction in the list will have been sent to address 0x0. I'm pretty sure this is how Etherscan works. I'm not sure about other blockchain scrapers. It will be obvious because the transaction will have a to value of 0x0 and the bytecode in the input data field.

If you're looking for a solution that reads directly from the blockchain (i.e. a locally running node), then the only way to find a contract's creation transaction (if you don't know the deploying account) is to scan the chain looking for the address of the contract you're interested in. Look in the transaction receipt's contractAddress data field. Any particular contract address will only ever appear once in a single transaction's receipt. And that transaction will be the transaction in which the contract was deployed.

If you’re lucky you will have written a “contractCreated” event in your deploying smart contract. You won’t be able to get the address during the transaction, but the event will tell you which transaction it is.

Answer 4

Otherwise more specifically you can use an attribute in your contract that will store the creator. This attribute can be read by any contract or dapp.

Example:

pragma solidity ^0.4.8;
contract myContract  {

    address public creator;

    function myContract() {
        creator = msg.sender;
    }
}

Answer 5

You can binary search on all blocks for existence of w3.eth.get_code. Given that at the time of this answer the ethereum chain is on block 15581647, it'll take about log2(15581647) = 24 calls to chain node to get to the creation transaction for that contract. The from field of that transaction will give you the creator of that contract.