DeepCAPTCHA: An image CAPTCHA based on depth perception

Hossein Nejati, Ngai-Man Cheung, Ricardo Sosa , Dawn C.I. Koh

Research output: Chapter in Book/Report/Conference proceedingConference PaperResearchpeer-review

15 Citations (Scopus)


Over the past decade, text-based CAPTCHA (TBC) have become popular in preventing adversarial attacks and spam in many websites and applications including emails services, social platforms, web-based market places, and recommendation systems. However, in addition to several problems with TBC, it has become increasingly difficult to solve in recent years, to keep up with OCR technologies. Imagebased CAPTCHA (IBC), on the other hand, is a relatively new concept that promises to overcome key limitations of TBC. In this paper we present an innovative IBC, Deep- CAPTCHA, based on design guidelines, psychological theory and empirical experiments. DeepCAPTCHA exploits the human ability of depth preception. In our IBC users should arrange 3D objects in terms of size (or depth). In our framework for DeepCAPTCHA, we automatically mine 3D models, and use a human-machine Merge Sort algorithm to order these unknown objects. We then create new appearances for these objects at multiplication factor of 200, and present these new images to the end-users for sorting (as CAPTCHA tasks). Humans are able to apply their rapid and reliable object recognition and comparison (arise from years experience with the physical environment) to solve DeepCAPTCHA, while machines are still unable to complete these tasks. Experimental results show that humans can solve DeepCAPTCHA with a high accuracy (∼ 84%) and ease, while machines perform dismally.

Original languageEnglish
Title of host publicationProceedings of the 5th ACM Multimedia Systems Conference
Place of PublicationNew York, USA
PublisherAssociation for Computing Machinery (ACM)
Number of pages10
ISBN (Electronic)9781450327053
Publication statusPublished - 2014
Externally publishedYes
EventACM Multimedia Systems Conference 2014 - , Singapore
Duration: 19 Mar 201421 Mar 2014
Conference number: 5th


ConferenceACM Multimedia Systems Conference 2014
Abbreviated titleMMSYS 2014
Internet address

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