When I sign a string with the web3.eth.sign() method and web3.eth.accounts.sign() method. The result value of the two signatures is different. I don't know why these two results are different.

I'm using the latest web3.js. And the private key is from metamask.

This is my code

await ethereum.enable();
web3 = new Web3(web3.currentProvider);

let accounts = await web3.eth.getAccounts();
let msg = "sign this message"
let prefix = "\x19Ethereum Signed Message:\n" + msg.length
let msgHash1 = web3.utils.sha3(prefix+msg)

let sig1 = await web3.eth.sign(msgHash1, accounts[0]);
let privateKey = "0xcfb51f3737044cb4bfb49cbb10ae67d79ee81523d7065e95972cc23ed914e95e"
let sigObj = await web3.eth.accounts.sign(msgHash1, privateKey)
let sig2 = sigObj.signature;

console.log(sig1)
console.log(sig2)

And this is result.

When I sign a string with the web3.eth.sign() method and web3.eth.accounts.sign() method. The result value of the two signatures is different. I don't know why these two results are different.

I'm using the latest web3.js. And the private key is from metamask.

This is my code

await ethereum.enable();
web3 = new Web3(web3.currentProvider);

let accounts = await web3.eth.getAccounts();
let msg = "sign this message"
let prefix = "\x19Ethereum Signed Message:\n" + msg.length
let msgHash1 = web3.utils.sha3(prefix+msg)

let sig1 = await web3.eth.sign(msgHash1, accounts[0]);
let privateKey = "0xcfb51f3737044cb4bfb49cbb10ae67d79ee81523d7065e95972cc23ed914e95e"
let sigObj = await web3.eth.accounts.sign(msgHash1, privateKey)
let sig2 = sigObj.signature;

console.log(sig1)
console.log(sig2)

And this is result.

• javascript
• ethereum
• web3js

• My guess is that one method adds message prefix, another does not. You can verify this by walking through the relevant source code with step-by-step debugger. – Mikko Ohtamaa Commented Nov 21, 2020 at 12:48

3 Answers 3

The source code shows that the difference is that web3.eth.accounts.sign prefixes and hashes the message before signing it.

In your example pass in msg instead of msgHash to eth.accounts.sign:

So this signature:

const msg = 'hello world'
const { signature } = await web3.eth.accounts.sign(msg, privateKey)

will produce the same signature as eth.sign with hashed message:

const msg = 'hello world'
const msgHash = web3.eth.accounts.hashMessage(msg)
const signature = await web3.eth.sign(accounts[0], msgHash)

The short answer is this is by design (for the best of my understanding), to prevent interpretation of a signed Ethereum transaction as other data (for example a meta transaction, verified by a smart contract logic).

More relevant details: https://ethereum.stackexchange./questions/35425/web3-js-eth-sign-vs-eth-accounts-sign-producing-different-signatures

web3.eth.sign and web3.eth.accounts.sign generate the same signature in web3.js v1.3.4 .

Correct me if I am wrong, It seems web3.eth.sign calls web3.eth.accounts.sign under the hood, here