Emerging Image Game CAPTCHAs for Resisting Automated and Human-Solver Relay Attacks

Abstract

CAPTCHAs represent an important pillar in the web security domain. Yet, current CAPTCHAs do not fully meet the web security requirements. Many existing CAPTCHAs can be broken using automated attacks based on image processing and machine learning techniques. Moreover, most existing CAPTCHAs are completely vulnerable to human-solver relay attacks, whereby CAPTCHA challenges are simply outsourced to a remote human solver. In this paper, we introduce a new class of CAPTCHAs that can not only resist automated attacks but can also make relay attacks hard and detectable. These CAPTCHAs are carefully built on the notions of dynamic cognitive games (DCG) and emerging images (EI), present in the literature. While existing CAPTCHAs based on the DCG notion alone (e.g., an object matching game embedded in a clear background) are prone to automated attacks and those based on the EI notion alone (e.g., moving text embedded in emerging images) are prone to relay attacks, we show that a careful amalgamation of the two notions can resist both forms of attacks. Specifically, we formalize, design and implement a concrete instantiation of EI-DCG CAPTCHAs, and demonstrate its security with respect to image processing and object tracking techniques as well as their resistance to and detectability of relay attacks.

Secure CAPTCHA by Genetic Algorithm (GA) and Multi-Layer Perceptron (MLP)

“…They prove that puzzle-based CAPTCHAs need less time than text-based ones. An extended version of [24] that uses animation effects was later developed in [25].…”

Building Emerging Images with Tiled Orders and Posets

“…Afterwards, they applied a series of countermeasures, such as pseudo-3D rotation, hidden edge segments, etc., to resist automated object recognition. Gao et al showed the weakness of 2D EIMO CAPTCHA, and they proposed a different design based on 3D objects and examined its security and usability [18,19].…”