When using web3.js to execute a function in a contract, I always get the following error: "authentication needed: password or unlock​." I know that I have to unlock account first via either geth console or web3.personal.unlockAccount(web3.personal.listAccounts[0],"", duration)​. However, it is not convenient to use console when the smart contract executes in the real network. Moreover, I am not comfortable to use web3.personal.unlockAccount​ because I have to provide the password of the account in the clear text. So, what is the best way to unlock account programmatically while still keeping the password secret?


1 Answer 1


You have a few options on how to obscure your password:

1) one simple way is I save a temp variable and clear my screen in console:

pw = ‘myPassword’;

control+k // clear screen

Then I can unlock and take my time with unlocking:

web3.personal.unlockAccount(web3.personal.listAccounts[0],pw, duration);

2) you can obscure it my creating your own UI to input the password and conceal it: <input type=“password” />

After you handle this input according to your preferred method of UI, then you need to do a bit more manual work of signing the raw transaction and sending it. You need to use a library like ethereumjs-tx.

You’d need to convert the function call into hex data, sign it with ethereumjs-tx, and then send the transaction with that signed data to the Blockchain. So a few more steps here.

3) You can use Metamask, and the signing is done through that. You’d need a Metamask enabled chrome browser, your accounts in that Metamask vault, and you’d need to use the Metamask-injected web3 and call the contract function through that.

4) You can use an app with a web3 browser like Mist or Parity; open your web app through their built in browsers, then you can sign through those apps.

  • and where is the correct answer? Uncaught Error: The MetaMask Web3 object does not support synchronous methods like personal_unlockAccount without a callback parameter. May 28, 2018 at 10:23

Not the answer you're looking for? Browse other questions tagged or ask your own question.