How do I generate a random mnemonic?

[GrandSchtroumpf]

It would be very convenient to add a method to the wordlists object to generate a random mnemonic string of 12 words.

[GrandSchtroumpf]

Here is a simple function to achieve this (in wordlists/lang-x.ts) :

generateWords(amount: number): string {
    loadWords(this);
    return Array(amount)
      .fill(null)
      .reduce((acc: number[], _) => {
        const getRandom = () => Math.floor(Math.random() * wordlist.length);
        let random = getRandom();
        while (acc.indexOf(random) !== -1) { random = getRandom(); }
        return [...acc, random];
      }, [])
      .map(index => wordlist[index])
      .join(' ');
}

[ricmoo]

You cannot use any random set of words, because there is a checksum in the result, so the last word in a mnemonic can be invalid if random.

This can be done safely though, using:

Wallet.createRandom().mnemonic

The word lists are meant just to be an abstraction if the BIP 039 lists. BIP 032 and BIP 044 are handled by utils.HDNode, so if you want a longer sequence of words you could use: utils.HDNode.entropyToMnemonic(utils.randomBytes(32))

Make sense?

[ricmoo]

Also, you can pass in options to specify the language, for example: Wallet.createRandom({ locale: wordlists.ja }).mnemonic. :)

[GrandSchtroumpf]

Ok, thanks for the workaround. Nevertheless, I don't think it's a good design to have to create a wallet to generate a list of words. createRandom will use the default path, and in my case, the user will generate many wallets with different derivation paths.
So why not add a function to wordlists/lang-x.ts that is safe like that :

import { fromMnemonic, entropyToMnemonic } from '../utils/hdnode';
import { randomBytes } from '../utils';
...
generate(amount: 16 | 32) {
    return entropyToMnemonic(randomBytes(16), this).split(' ');
}

[ricmoo]

It's not really a work-around, it is just "the correct way to do it". :)

A Wordlist is just a word list, and should not have and does not need any complex dependencies for doing maths. The maths for computing an HDNode is already included in HDNode, which takes in a word list. Imagine if a person just wanted the Wordlist operations (getWordByIndex, getIndexForWord); by coupling them, you would cause someone who only needs 10kb of library to now pull in 65kb of library (HMAC + PBKDF2 + SHA-512 + secp256k1) that they will never use.

In general coupling parts of the library that have a logical separation not good design. That is why we have a nice clean interface that is actually a leaf in the dependency tree.

Keep in mind any length congruent to 0 mod 3, greater than 12 and less than 24 (inclusive) is permitted (i.e. word lengths of 12, 15, 18, 21, 24), not just 16 and 24.

You can specify a path as well:

Wallet.createRandom({
    locale: wordlists.it,
    path: "m'/0'" // something weird an non-standard.

You can also access the same behaviour by using HDNode directly, if you wish to store intermediate nodes to speed up generation:

let node = utils.HDNode.fromSeed(utils.random(16));
let intermediateNode = node.derive("m/44'/60'/0'/0");
for (let j = 0; j < 10; j++) {
    console.log(intermediateNode.derive(String(i)).privateKey);
}

but keep in mind a BIP 39 wallet requires a path, which Wallet encodes, but an HDNode does not.

[GrandSchtroumpf]

Ok, I see your point. Sorry for the "workaround" word misused.
Then maybe, just add an example in the doc after the load mnemonic phrase of this page =) :
https://docs.ethers.io/ethers.js/html/api-wallet.html#creating-instances

[ricmoo]

:)

Yupp, I’ve made a note to add an example to the Cookbook too. I’ll leave this ticket open to remind me.

Thanks! :)

[ricmoo]

I've added this to the cookbook: https://docs.ethers.io/ethers.js/html/cookbook-accounts.html#random-mnemonic

Thanks! :)

[deuchainn]

I've added this to the cookbook: https://docs.ethers.io/ethers.js/html/cookbook-accounts.html#random-mnemonic

Thanks! :)

This is gone from the latest documentation, how would one go to create a new wallet that uses a mnemonic phrase say of 24 words?

[deuchainn]

I've added this to the cookbook: https://docs.ethers.io/ethers.js/html/cookbook-accounts.html#random-mnemonic
Thanks! :)

This is gone from the latest documentation, how would one go to create a new wallet that uses a mnemonic phrase say of 24 words?

Found out how do it:

import { Wallet, utils } from 'ethers';

const wallet = Wallet.fromMnemonic(
  utils.entropyToMnemonic(utils.randomBytes(32))
)

console.log('wallet.address:', wallet.address)
console.log('wallet.mnemonic.phrase:', wallet.mnemonic.phrase)
console.log('wallet.privateKey:', wallet.privateKey)