Creating hash of a struct in Solidity and JavaScript

Question

I have created a message hash in JavaScript using:

let message = {
        'message': 'Receiver closing signature',
        'sender': sender,
        'balance': value
};

message = web3.utils.toHex(message);
let messageHash = web3.utils.sha3(message);

How should I define the equivalent object in solidity, and what function should I use to get the same message hash.

Answer 1

My suggestion is to use the abi.encode method in solidity, and the equivalent web3.eth.abi.encodeParameters in web3.js.

Something like this:

Solidity Source

pragma solidity ^0.4.24;

contract test{

    struct mStruct {
        string message;
        address sender;
        uint balance;
    }

    function testme() public pure returns(bytes32) {

        mStruct memory message = mStruct("Receiver closing signature", 0xCA35b7d915458EF540aDe6068dFe2F44E8fa733c, 100);
        return keccak256(abi.encode(message.message, message.sender, message.balance));
    }
}

Result:

0x4006e807f707d49e72276526e1106236184a868f6a142ca286ae0583556bacfb

JavaScript Source

message = {
    'message': 'Receiver closing signature',
    'sender': '0xCA35b7d915458EF540aDe6068dFe2F44E8fa733c',
    'balance': 100
};

encoded = web3.eth.abi.encodeParameters(['string', 'address', 'uint'],[message.message, message.sender, message.balance])

hash = web3.utils.keccak256(encoded)

Result:

"0x4006e807f707d49e72276526e1106236184a868f6a142ca286ae0583556bacfb"