Devanagari CAPTCHA: For the Security in Web

Abstract

Completely Automated Public Turing Test to Tell Computers and Humans Apart or CAPTCHA is a solution for cyber-attack. CAPTCHA is a small challenge that an internet user has to pass before accessing any online service. The most common type of CAPTCHA is text-based CAPTCHA, in which a small image (contains a random number of alphabets) is presented before the user. The user has to identify and then type the alphabet in a text box. The textual information in the CAPTCHA must not be identified by a bot (computer code). So, artificial noise and distortion are applied in the image. Earlier text-based schemes use English alphabets, but over time non-English language-based text CAPTCHAs also came into the picture. Native language-based text CAPTCHA is very useful for internet users who do not know the English language. This article is an effort towards the current status of the Devanagari script-based CAPTCHAs. We have analyzed 28 unique Devanagari CAPTCHAs from a security and usability point of view. Total 28000 different samples are collected for this experiment. For the success of a text-based CAPTCHA, it must be very secure from the bot and easy for human beings. Devanagari CAPTCHA can be very beneficial for Indian websites. This paper is written by keeping the importance of Devanagari script-based CAPTCHA.