Simple Question on ecrecover

Question

I think that I can verify a hash of a message using my signature within a Solidity contract, something like this:

contract ecrecover {
    function testRecovery(bytes32 hash, bytes signature) returns (address) {
    bytes32 r;
    bytes32 s;
    uint8 v;
    assembly {
      r := mload(add(signature, 32))
      s := mload(add(signature, 64))
      v := and(mload(add(signature, 65)), 255)
    }
    if (v < 27) v += 27;
    address addr = ecrecover(hash, v, r, s);
    return addr;
    }

I am unclear how to generate the hash or signature given my message and private key. For example, say my message is the string: I am Eric

My account data are:

address: 0x9858EfFD232B4033E47d90003D41EC34EcaEda94

Private Key: 0x1ab42cc412b618bdea3a599e3c9bae199ebf030895b039e9db1e30dafb12b727

How would I generate the hash and signature of my message?

Answer 1

The following should work:

let signature = web3.eth.accounts.sign (
  'I am Eric',
  '0x1ab42cc412b618bdea3a599e3c9bae199ebf030895b039e9db1e30dafb12b727');
let hash = web3.eth.accounts.hashMessage('I am Eric');

See eth.accounts.sign, web3.eth.accounts.hashMessage documentation for details.