private function extractKeyAndIV(PhabricatorFile $file)
{
$outer_iv = $file->getStorageProperty('iv.base64');
$outer_iv = base64_decode($outer_iv);
$outer_iv = new PhutilOpaqueEnvelope($outer_iv);
$outer_payload = $file->getStorageProperty('payload.base64');
$outer_payload = base64_decode($outer_payload);
$outer_key_name = $file->getStorageProperty('key.name');
$outer_key = $this->getMasterKeyMaterial($outer_key_name);
$payload = $this->decryptData($outer_payload, $outer_key, $outer_iv);
$payload = phutil_json_decode($payload);
$inner_iv = $payload['iv.base64'];
$inner_iv = base64_decode($inner_iv);
$inner_iv = new PhutilOpaqueEnvelope($inner_iv);
$inner_key = $payload['key.base64'];
$inner_key = base64_decode($inner_key);
$inner_key = new PhutilOpaqueEnvelope($inner_key);
return array($inner_key, $inner_iv);
}