Strong multilingual CAPTCHA based on handwritten characters

CAPTCHA (Completely Automated Public Turing Test to tell Computers and Humans Apart) is a kind of test which is commonly used by different websites on the Internet to differentiate between humans and automated bots. Most websites require the user to pass the CAPTCHA before signing up or filling out most forms. CAPTCHA today is even used on some mobile applications to provide a higher security level that can protect websites and mobile applications against malicious attacks by automated bots and spammers. In this paper, we present an advanced CAPTCHA technique; our technique essentially relies on employing the human recognition ability, which is not available in automated bots or machines, through leveraging the handwriting characteristics in designing CAPTCHA. Moreover, the proposed CAPTCHA technique adopts handwritten characters of four different languages (English, Arabic, Spanish, and French) to generate handwritten multilingual CAPTCHA text using characters from the four adopted languages. Furthermore, the initial experiments' results have shown a promising security level that the proposed CAPTCHA technique can provide.