QA: Generate ED25519 recovery phrase

[SimiHunjan]

Generate a recovery phrase that results in deriving ED25519 key types.

• Generate a 12 word recovery phrase
• Generate a 24 word recovery phrase
• Generate a private key from the 12 word recovery phrase
• Generate a private key from the 24 word recovery phrase
• Use the 12 word recovery phrase to regenerate a key
• Use the 24 word recovery phrase to regenerate a key

[SimiHunjan]

I am little unclear on the mnemonic feature we have support for (in general as this question is applicable to all SDKs). I can see we support 12 and 24 word mnemonic phrase generation. Initially we only supported ED25519 keys so it was obvious the recovery phrase feature would generate a recovery phrase and then you could generate an associated ED25519 key. Now we support both ED25519 and ECSDA. What I am unclear on is when I use:

const MnemonicBIP39 mmneumonic = MnemonicBIP39::generate12WordBIP39Mnemonic();
std::cout << "Generate a 12 word recovery phrase: " << mmneumonic.toString() << std::endl;

How do I know which key type this mnemonic is going to generate keys for? Or do I specify that after I create the mnemonic/recovery phrase? I know that for ED key generation there is an index for every key and if you want to regenerate keys from a recovery phrase you have to also provide the index. Also is the above code snippet correct in what I am trying to achieve.

[SimiHunjan]

Code Example

  // Generate a ED25519 recovery phrase
  const MnemonicBIP39 mneumonic1 = MnemonicBIP39::generate12WordBIP39Mnemonic();

  std::cout << "Generated a 12 word recovery phrase: " << mneumonic1.toString() << std::endl;

  const MnemonicBIP39 mneumonic2 = MnemonicBIP39::generate24WordBIP39Mnemonic();
  std::cout << "Generated a 24 word recovery phrase: " << mneumonic2.toString() << std::endl;

Output

Generated a 12 word recovery phrase: install recipe barely viable bring diesel dash obscure ship dignity tomorrow reform

Generated a 12 word recovery phrase: man smile grief seed property pear exclude rib when always mosquito honey plate tennis reward extend potato matrix bag cream couch outdoor course action

[rwalworth]

One mnemonic can generate ED25519 and ECDSAsecp256k1 keys; mnemonics aren't specific to one type of key. In the MnemonicBIP39 object, there are toStandardEd25519PrivateKey and toStandardECDSAsecp256k1PrivateKey functions that can generate the SLIP-44 standard private keys for those mnemonics. So it would look something like (using ED25519):

const MnemonicBIP39 mnemonic = MnemonicBIP39::generate12WordBIP39Mnemonic();
const std::shared_ptr<PrivateKey> privateKey = mnemonic.toStandardED25519PrivateKey();

As for the index, it's just the final derivation in the full SLIP-44 standard deviation path. It can be used to generate multiple different keys from the same mnemonic. It is defaulted in the C++ SDK to 0, but a user can provide a specific index if they so like. So that would look something like (using ECDSA this time):

const std::shared_ptr<PrivateKey> privateKeyIndex0 = mnemonic.toStandardECDSAsecp256k1PrivateKey();
const std::shared_ptr<PrivateKey> privateKeyIndex1 = mnemonic.toStandardECDSAsecp256k1PrivateKey("", 1);

The "" is an optional passphrase as well that you can provide.

const std::shared_ptr<PrivateKey> privateKeyNoPassphraseOrIndex = mnemonic.toStandardECDSAsecp256k1PrivateKey();
const std::shared_ptr<PrivateKey> privateKeyPassPhraseNoIndex = mnemonic.toStandardECDSAsecp256k1PrivateKey("passphrase");
const std::shared_ptr<PrivateKey> privateKeyNoPassphraseIndex = mnemonic.toStandardECDSAsecp256k1PrivateKey("", index);
const std::shared_ptr<PrivateKey> privateKeyPassphraseAndIndex = mnemonic.toStandardECDSAsecp256k1PrivateKey("passphrase", index);