Designing Secure and Usable CAPTCHA in Hindi Language

Abstract

Completely Automated Public Turing test to tell Computers and Humans Apart (CAPTCHA) is a popular term used for Human Interaction Proofs. After getting such a high breaking rate of all kinds of CAPTCHAs, it is a dire need to find an alternate solution. The 4th widely spoken language in the world is also Hindi. It motivated us to design a text-based CAPTCHA in the Hindi language. Some Hindi language-based CAPTCHAs exist, but security testing is not done on these designs. We collected 20 unique Hindi CAPTCHAs to test the security. We achieved 57% to 93% breaking rate for collected 20 CAPTCHA schemes. We derived some benchmarks to design a more secure and useable CAPTCHA and developed a novel Hindi CAPTCHA. The length of the proposed Hindi CAPTCHA varies from 5 to 8 characters. It has a combination of 5 different segments. We have generated two versions of the proposed CAPTCHA. We tried to break these schemes with the proposed CAPTCHA breaking algorithms. We have achieved a low segmentation rate for Version 1.0 and Version 2.0 that ranges from 0.12% to 7.16% and 0% to 2.03% respectively. Both versions are segment proof. For testing usability, we generated 1200 CAPTCHA samples of each version. In the usability testing, 60 users have participated. We got 90.67% and 62.34% recognition accuracy for Version 1.0 and Version 2.0. The average time to solve a single image was about 10.13 seconds and 13.5 seconds for Version 1.0 and Version 2.0, respectively. It places Version 1.0 in the sweet spot that is the desired property of a CAPTCHA. newline