1.
Asif Hasnain
– Comsats Institute of Information Technology Islamabad, Pakistan
2.
Waqas Malik
– Comsats Institute of Information Technology Islamabad, Pakistan
3.
Mohsin Yaseen
– Comsats Institute of Information Technology Islamabad, Pakistan
4.
Syed Jawad Hussain Shahzad
– Comsats Institute of Information Technology Islamabad, Pakistan
Abstract
CAPTCHA [1; 2] (Reverse Turing Test) is an authorization
test to ensure that response is coming from
human. Over the years, its design has been vulnerable
to different attacks that utilize the visual appearance
of challenge. Therefore, designing a highly robust
and usable CAPTCHA that can resist such attacks is
highly desirable. The study proposes a novel scheme,
named Scratch CAPTCHA. It is based on a new paradigm
which emphasizes the notion that strength of
the CAPTCHA must be formulated by the secrecy of
challenge. We have tested the robustness of our idea
against a simple bot attack that successfully emulates
human behavior (or actions) but not their intelligence.
