how to get public key by the transaction hash?

Question

For example, this is the transaction hash in goerli: 0x60605c7e3fddd2be1fa63f4fa8ef12bfc5e5c69062c6a4788d1277e007e7de02.

We know that the public key can be derived by ECDSA. And we can get v,r,s from transaction hash. So transaction hash => vrs => ECDSA => public key. How to get the public key by the transaciton hash? I want to get some code. Thx!

Answer 1

Here's a Node.js script that uses ethers.js version 5.4.x:

const { ethers } = require("ethers");

// Function to extract the address associated with to a transaction
async function getPublicKeyFromTransactionHash(provider, txHash) {
  // Fetch the transaction using the transaction hash and provier
  const tx = await provider.getTransaction(txHash);

  // Extract the all the relevant fields from the transaction (We need all of them)
  const unsignedTx = {
    gasLimit: tx.gasLimit,
    value: tx.value,
    nonce: tx.nonce,
    data: tx.data,
    chainId: tx.chainId,
    to: tx.to,
    type: tx.type,
    maxFeePerGas: tx.maxFeePerGas,
    maxPriorityFeePerGas: tx.maxPriorityFeePerGas,
  };

  // Serializing tx without the signature
  const serializedTx = ethers.utils.serializeTransaction(unsignedTx);

  // Extract the signature (v, r, s) from the transaction
  const { v, r, s } = tx;
  
  // Join splitted signature
  const signature = ethers.utils.joinSignature({ v, r, s });

  // Recover the address or public key with (replace recoverAddress by recoverPublicKey) associated with the transaction
  return ethers.utils.recoverAddress(
    ethers.utils.keccak256(serializedTx),
    signature
  );
}

// Call the function with a provider and a transaction hash
(async () => {
  // Public provider for Goerli
  const provider = new ethers.providers.JsonRpcProvider(
    "https://ethereum-goerli-rpc.allthatnode.com"
  );

  // Transaction hash
  const txHash =
    "0x60605c7e3fddd2be1fa63f4fa8ef12bfc5e5c69062c6a4788d1277e007e7de02";

  // And finally call the function to extract the address associated with the transaction
  const address = await getPublicKeyFromTransactionHash(provider, txHash);

  console.log("Address:", address);
})();

Answer 2

To get the public key associated with a transaction hash, you will need to use a block explorer. A block explorer is a search engine that allows users to easily look up information on the blockchain. Once you have the block explorer open, enter the transaction hash into the search bar and the public key associated with the transaction will be displayed.

Answer 3

You can check this out if you're looking for a solution of this problem in golang: https://github.com/ashish10677/public-key-extractor