Function get64ByteSeedFromMnemonic

get64ByteSeedFromMnemonic(
seedPhrase: string | string[],
passphrase?: string,
): Promise<Uint8Array>
Derives the 64-byte BIP39 seed from a mnemonic phrase using PBKDF2 (PBKDF2-HMAC-SHA512, 2048 iterations, salt "mnemonic" + passphrase). This is the standard BIP39 derivation: the full 512-bit seed is returned unmodified and serves as the input key material for identity derivation (Identity.fromSeed applies HKDF-SHA256 on top).

Both 12-word (128-bit) and 24-word (256-bit) mnemonics produce the same 64-byte seed length, per the BIP39 standard.
Parameters
- seedPhrase: string | string[]
  The BIP39 mnemonic phrase (string or array of words).
- passphrase: string = ''
  Optional BIP39 passphrase ("25th word"). BIP39 NFKD normalization (mnemonic and passphrase) is performed by @scure/bip39; this function passes the passphrase through unchanged. An empty string (default) matches phrases without a passphrase. WARNING: the passphrase is NOT recoverable — a different passphrase silently derives a completely different seed with no error indication. Store it as carefully as the mnemonic itself.
Returns Promise<Uint8Array>
A Promise resolving to the 64-byte Uint8Array BIP39 seed.
Example
```
const seed = await get64ByteSeedFromMnemonic('abandon abandon ... art');
// Uint8Array(64) [94, 176, 187, ...]

const seedWithPassphrase = await get64ByteSeedFromMnemonic(words, 'my secret 25th word');
```
- Defined in packages/core/src/seed.ts:166