I'm struggling to match two hashes. I hash a Json in String format in my Smart Contract like this.

   function verifyProof(string calldata _fullProof) public returns(bool r){
        bytes32 hashed = keccak256(abi.encodePacked(_fullProof));

I'm interacting with the Smart Contract via a external Truffle Script that I execute with the command "truffle exec truffle_script.js

In the Script I've been trying various methods to archive the same hash:

    const hashedLocal = web3.utils.soliditySha3(web3.utils.encodePacked(JSON.stringify(proof)));
    console.log("hashed local2", hashedLocal)
    console.log("hashed local3",web3.utils.keccak256(web3.utils.encodePacked(toString(proof))));
   console.log("hashed local3.5", web3.utils.keccak256(proof));
   console.log("hashed local4", web3.utils.keccak256(JSON.stringify(proof)));
   console.log("hashed local4", web3.utils.keccak256(toString(proof)));
   console.log("hashed local5" ,web3.utils.soliditySha3({t: 'string', v: proof}));
   console.log("hashed local6" ,web3.utils.soliditySha3({t: 'string', v: toString(proof)}));
   console.log("hashed local7" ,web3.utils.soliditySha3(web3.utils.toHex(proof) ));

I simply can't produce the same hash.

Does anybody have an idea what the problem might be?

The data to hash looks like this:

{"proof": {
    "a": [
    ],"b": [
    ],"c": [
"inputs": [

1 Answer 1


here is the solidity code:

    function hash(string calldata data) public pure returns(bytes32){
        return keccak256(abi.encodePacked(data));

and here is JS code:


these two codes return similar data for "hello" as input. I think you problem is inputs for these two functions, check you inputs and try simple inputs and check for uppercase and lowercase letters.

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