Mnemonics and Keys

This section explains how to generate mnemonics, derive keys and get a key pair

• Mnemonic generation

• Key pair generation from mnemonic

• Key pair generation without mnemonic

• Keys derivation

  • Master (root) key

  • Derived key

  • Generate keys for signature

Check crypto module reference for more info:

Mnemonic generation

To generate a random mnemonic, use mnemonic_from_random function. Specify the dictionary, and a number of words (12 or 24).

const SEED_PHRASE_WORD_COUNT = 12; //Mnemonic word count
const SEED_PHRASE_DICTIONARY_ENGLISH = 1; //Dictionary identifier

const { phrase } = await client.crypto.mnemonic_from_random({
    dictionary: SEED_PHRASE_DICTIONARY_ENGLISH,
    word_count: SEED_PHRASE_WORD_COUNT,
});
console.log(`Generated seed phrase "${phrase}"`);

Result:

Generated seed phrase: "garden wedding range mixed during left powder grid modify safe recycle cup"

Key pair generation from mnemonic

Here is the fast way to generate a key pair for a signature from a specified mnemonic and path with mnemonic_derive_sign_keys method.

const HD_PATH = "m/44'/396'/0'/0/0";

const keyPair = await client.crypto.mnemonic_derive_sign_keys({
    phrase,
    path: HD_PATH,
    dictionary: SEED_PHRASE_DICTIONARY_ENGLISH,
    word_count: SEED_PHRASE_WORD_COUNT,
});
console.log(`Generated key pair:`);
console.log(keyPair);

Result:

Generated key pair:
{
  public: '4085d11b6d607c44ef0e8ddc535786af1a4b1f971e758206cd222ed3eba47d8b',
  secret: 'e90866b307ea6a72c216a34786762e648e9b382779fdfb88cf7b1e900a6bf0e2'
}

See the Keys derivation section for more information about the algorithm that is used in mnemonic_derive_sign_keys.

Key pair generation without mnemonic

Sometimes there is no need for mnemonic.

For example, if you generate a key pair for a server that does not need a readable form. Then you can easily generate such a pair with generate_random_sign_keys function:

const simpleKeys = await client.crypto.generate_random_sign_keys();
console.log(`key pair not from mnemonic:`);
console.log(simpleKeys);

Result:

key pair not from mnemonic:
{
  public: 'de996e3004e2bc73b47e8a4fce665847194e2245ddbfc30d9ec2014913249f50',
  secret: 'a761156ff1ad497d4d52a32e32720cc3ef8b0d7c259f6d91b9f236d6288e12a3'
}

Great! Now you can use this key pair in methods of contracts module, such as abi.encode_message, abi.encode_message_body, etc.

Keys derivation

Master (root) key

To derive a key within a specified path, first, you need to generate a seed from the given mnemonic and then get the extended master private key that will be the root for all the derived keys.

Both these operations can be performed with hdkey_xprv_from_mnemonic method:

const hdk_root = await client.crypto.hdkey_xprv_from_mnemonic({
        dictionary: SEED_PHRASE_DICTIONARY_ENGLISH, // 1
        wordCount: SEED_PHRASE_WORD_COUNT, // 12
        phrase: seedPhrase
    });
console.log(`\nSerialized extended master private key: \n${hdk_root}`);

Result:

Serialized extended master private key: 
xprv9s21ZrQH143K45hXeaopM1rAUJDszLAcwFkxrZ4njANoGhFPYFsB7rzspWC8wAnWoZ2bPia7covh3mVVboC2nEswu18iEHs5LjVknSWMR2w

Derived key

Now you can derive the key within the specified path with hdkey_derive_from_xprv_path method. The result will be an extended derived private key.

const HD_PATH = "m/44'/396'/0'/0/0";
const extended_prkey = await client.crypto.hdkey_derive_from_xprv_path({
    xprv: hdk_root,
    path: HD_PATH,
});
console.log(`Serialized derived extended private key: \n${extended_prkey}`);

Result:

Serialized derived extended private key: 
xprvA45BBKdrZKobCbeFvC316LZ6AVDXbDn8Sa3btCMCcgTRM4CRxX4Tg3fk7sNNXPza9aMiS6mBMp7wfHdmT23bri6YgwHbTJgXqKnJNNHAw98

Now lets extract the private key itself from the extended key with function:

const secret = await сlient.crypto.hdkey_secret_from_xprv(extended_prkey);
console.log(`Derived private key: \n${secret}`);

Result:

Derived private key: 
e90866b307ea6a72c216a34786762e648e9b382779fdfb88cf7b1e900a6bf0e2

Generate keys for signature

After we've got the derived private key we can generate a ed25519 key pair for signature:

let keyPair2 = await сlient.crypto.nacl_sign_keypair_from_secret_key({ secret })

if (keyPair2.secret.length > keyPair2.public.length) {
keyPair2.secret = keyPair2.secret.substring(0, keyPair2.public.length);
}
console.log(`Key pair for signature:`);
console.log(keyPair2);

Result:

Key pair for signature:
{
  public: '4085d11b6d607c44ef0e8ddc535786af1a4b1f971e758206cd222ed3eba47d8b',
  secret: 'e90866b307ea6a72c216a34786762e648e9b382779fdfb88cf7b1e900a6bf0e2'
}

Great! Now you can use this key pair in methods of contracts module, such as abi.encode_message, abi.encode_message_body, etc.