How to generate an Ethereum "brain wallet" in Javascript?

Question

Namely, enter string -> get private key?

Answer 1

Answer by Vitalik Buterin on reddit:

Try:

function brainwallet(username, password, hardness) {
    return web3.sha3(Array(hardness + 1).join(username + ":" + password));
}

Set hardness to something reasonably large, at least 2000. Use your usual username for username, even if lots of people know it. These two things together give you a ~20 bit-of-entropy improvement in security over the simple "sha3 of your string" approach at basically no cost to hardness of memorization.