Authors: Ankit Thakkar; Kajol Patel
Addresses: Department of Information Technology, Institute of Technology, Nirma University, Ahmedabad – 382 481, Gujarat, India ' Department of Computer Engineering, Institute of Technology, Nirma University, Ahmedabad – 382 481, Gujarat, India
Abstract: Nowadays online transactions are becoming ubiquitous that must be protected from bots using different techniques, and CAPTCHA is one of them. Text-CAPTCHA preferred due to its simplicity amongst different types of CAPTCHAs. Text-CAPTCHA can be strengthened by adding some distortion to prevent bot-attacks but cause usability issues for humans. This results in multiple attempts by a user to gain access to the required service and may give frustration to the user. Hence, there is a need to design CAPTCHA which is easy for humans to recognise but difficult for bots. This paper proposes virtual keyboard-based simple and efficient text-CAPTCHA verification scheme (VIKAS) that makes CAPTCHA verification easy for humans but difficult for bots. VIKAS uses simple text-CAPTCHA and verifies the same using positions of the keys pressed by the user using an image-based virtual keyboard. VIKAS is sustainable against segmentation scheme, replay attacks and possible attacks with keyloggers.
Keywords: completely automated public Turing test to tell computers and humans apart; CAPTCHA; virtual keyboard; bots; position-based verification; response time analysis.
International Journal of Information and Computer Security, 2020 Vol.12 No.1, pp.90 - 105
Received: 31 May 2018
Accepted: 11 Sep 2018
Published online: 04 Dec 2019 *