public function getSignature(): string
	{
		$input = $this->getArgs();

		$items = [];
		foreach ($input as $key => $val) {
			$items[] = sprintf('%s=%s', $key, $val);
		}

		$items[] = 'password=' . $this->getMerchantConfig()->password;

		return self::hashFunction(implode('&', $items));
	}