childKey method
Derives a child key at the given index.
Implementation
@override
Zip32Sapling childKey(Bip32KeyIndex index, ZCryptoContext context) {
final extendedKey = keyDerivator.deriveExpandedSpendingKey(
parent: privateKey,
index: index,
);
return Zip32Sapling(
privateKey: extendedKey,
publicKey: extendedKey.toExtendedFvk(),
);
}