public function sign($key, $password = null)
    {
        OpenSslException::reset();

        if (false === extension_loaded('openssl')) {
            // @codeCoverageIgnoreStart
            throw OpenSslException::create(
                'The "openssl" extension is not available.'
            );
            // @codeCoverageIgnoreEnd
        }

        if (false === ($resource = openssl_pkey_get_private($key, $password))) {
            // @codeCoverageIgnoreStart
            throw OpenSslException::lastError();
            // @codeCoverageIgnoreEnd
        }

        if (false === openssl_pkey_export($resource, $private)) {
            // @codeCoverageIgnoreStart
            throw OpenSslException::lastError();
            // @codeCoverageIgnoreEnd
        }

        if (false === ($details = openssl_pkey_get_details($resource))) {
            // @codeCoverageIgnoreStart
            throw OpenSslException::lastError();
            // @codeCoverageIgnoreEnd
        }

        $this->phar->setSignatureAlgorithm(Phar::OPENSSL, $private);

        if (false === @file_put_contents($this->file . '.pubkey', $details['key'])) {
            throw FileException::lastError();
        }
    }