/**
* Derive a child key
*
* @param $sequence
* @return HierarchicalKey
* @throws \Exception
*/
public function deriveChild($sequence)
{
$chain = Buffer::hex($this->ecAdapter->getMath()->decHex($this->getChainCode()), 32);
$hash = Hash::hmac('sha512', $this->getHmacSeed($sequence), $chain);
$offset = $hash->slice(0, 32);
$chain = $hash->slice(32);
if (false === $this->ecAdapter->validatePrivateKey($offset)) {
return $this->deriveChild($sequence + 1);
}
return new HierarchicalKey($this->ecAdapter, $this->getDepth() + 1, $this->getChildFingerprint(), $sequence, $chain->getInt(), $this->isPrivate() ? $this->ecAdapter->privateKeyAdd($this->getPrivateKey(), $offset->getInt()) : $this->ecAdapter->publicKeyAdd($this->getPublicKey(), $offset->getInt()));
}
/**
* @param int $tweak
* @return PublicKeyInterface
*/
public function tweakAdd($tweak)
{
return $this->ecAdapter->publicKeyAdd($this, $tweak);
}
