protected function getBlocktrailPublicKey($path) {
        $path = BIP32Path::path($path);

        $keyIndex = str_replace("'", "", $path[1]);

        if (!isset($this->blocktrailPublicKeys[$keyIndex])) {
            throw new \Exception("No blocktrail publickey for key index [{$keyIndex}]");
        }

        return $this->blocktrailPublicKeys[$keyIndex];
    }