Design of Secure Multilingual CAPTCHA Challenge

Abstract

Growing demand for native languages in web applications has made multilingual implementation of web user interfaces and dialogs essential. However, use of insecure foreign language text CAPTCHA challenges to prove human interaction in the native language pages of web applications has rendered CAPTCHA protected services unusable, insecure and inaccessible. This paper analyses CAPTCHA and multilingual functionalities of 410 multilingual websites (240 government and 170 non-government) and discusses their accessibility and usability. It enumerates deficiencies of currently in use CAPTCHA scripts and services (open and closed source). It discusses the design, algorithm, pseudo code, and working of a secure multilingual text CAPTCHA script having desired security, accessibility and usability features. The designed script offers localized onscreen keyboard, random patterns, fonts, and audio alternatives to improve usability and security. The results of experiments, security tests, and users study with the CAPTCHA tests generated through the proposed technique have validated its design, security, usability, and accessibility.