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September 12, 2017 | 11:30 a.m. - 12:20 p.m.
Category: Seminar
Location: Science Hall #1109 | Map
5045 Cass
Detroit, MI 48201
Cost: Free
Audience: Academic Staff, Alumni, Community, Current Graduate Students, Current Undergraduate Students, Faculty, Prospective Students, Staff

Game CAPTCHAs for Resisting Automated and Human-Solver Relay Attacks


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 talk, I will 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.


Chengcui Zhang is a Professor of Computer Science at the University of Alabama at Birmingham (UAB). She works in the broad areas of multimedia databases and information retrieval, multimedia data mining, multimedia security and forensics, Geoinformatics, and applied Bioinformatics. She has published over 160 refereed articles, many at the top tier venues in computer sciences including IEEE Transactions, IEEE Multimedia, ACM Multimedia (MM), IEEE International Conference on Data Mining 

(ICDM), ACM Conference on Communication and Computer Security (CCS), and IEEE International Conference on Multimedia and Expo (ICME). Dr. Zhang’s research has been externally supported by NSF, NIH, and by awards/gifts from the industry, including IBM, eBay, and Comcast. Dr. Zhang was the former Chair of IEEE Technical Committee on Semantic Computing and has been serving as the Conference Chair for IEEE Technical Committee on Multimedia Computing. She has also served in leading roles for many IEEE and ACM conferences, including a program chair for IEEE ICME’14, three times as a program chair for IEEE International Conf. on Information Reuse and Integration (IRI), two times as a program chair for IEEE International Symposium on Multimedia (ISM), and a program chair for the FTRA International Conference on Information Technology Convergence and Services, etc. She is an Associate Editor of IEEE Transactions on Multimedia and International Journal of Multimedia Data Engineering and Management.

For more information about this event, please contact LaNita Stewart at 7-2478 or