derive method
Implementation
@override
DerivedSecretKey derive(int index) {
final hardened = index >= DerivedKey.hardenBit;
final mat = VaultKeeper.vault.keyForge.deriveChild(
parentKey: secretKey.bytes,
parentChainCode: chainCode,
index: index,
hardened: hardened,
isPrivate: true,
parentPublicKey: publicKey.bytes,
);
return DerivedSecretKey(
secretKey: SecretKey(mat.key),
chainCode: mat.chainCode,
depth: depth + 1,
index: index,
parentFingerprint: fingerprint,
);
}