Usability and security of Arabic text-based CAPTCHA using visual cryptography

Abstract

Recently, with the spread of online services involving websites, attackers have the opportunity to expose these services to malicious actions. To protect these services, A Completely Automated Public Turing Test to Tell Computers and Humans Apart (CAPTCHA) is a proposed technique. Since many Arabic countries have developed their online services in Arabic, Arabic text-based CAPTCHA has been introduced to improve the usability for their users. Moreover, there exist a visual cryptography (VC) technique which can be exploited in order to enhance the security of text-based CAPTCHA by encrypting a CAPTCHA image into two shares and decrypting it by asking the user to stack them on each other. However, as yet, the implementation of this technique with regard to Arabic text-based CAPTCHA has not been carried out. Therefore, this paper aims to implement an Arabic printed and handwritten text-based CAPTCHA scheme based on the VC technique. To evaluate this scheme, experimental studies are conducted, and the results show that the implemented scheme offers a reasonable security and usability levels with text-based CAPTCHA itself.