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Nowadays, people generate and share massive content on online platforms (e.g., social networks, blogs). In 2021, the 1.9 billion daily active Facebook users posted around 150 thousand photos every minute. Content moderators constantly…

Cryptography and Security · Computer Science 2022-04-05 Mauro Conti , Luca Pajola , Pier Paolo Tricomi

CAPTCHAs remain a critical defense against automated abuse, yet modern systems suffer from well-known limitations in usability, accessibility, and resistance to increasingly capable bots and low-cost CAPTCHA farms. Behavioral and…

Cryptography and Security · Computer Science 2026-03-09 Shovon Paul , Md Imran Hossen , Xiali Hei

Providing security for webservers against unwanted and automated registrations has become a big concern. To prevent these kinds of false registrations many websites use CAPTCHAs. Among all kinds of CAPTCHAs OCR-Based or visual CAPTCHAs are…

Computer Vision and Pattern Recognition · Computer Science 2014-10-17 Ariyan Zarei

Previous work showed that reCAPTCHA v2's image challenges could be solved by automated programs armed with Deep Neural Network (DNN) image classifiers and vision APIs provided by off-the-shelf image recognition services. In response to…

Cryptography and Security · Computer Science 2021-04-09 Md Imran Hossen , Yazhou Tu , Md Fazle Rabby , Md Nazmul Islam , Hui Cao , Xiali Hei

To enhance the security of text CAPTCHAs, various methods have been employed, such as adding the interference lines on the text, randomly distorting the characters, and overlapping multiple characters. These methods partly increase the…

Cryptography and Security · Computer Science 2023-08-17 Ran Jiang , Sanfeng Zhang , Linfeng Liu , Yanbing Peng

Human Interactive Proofs (HIPs) are automatic reverse Turing tests designed to distinguish between various groups of users. Completely Automatic Public Turing test to tell Computers and Humans Apart (CAPTCHA) is a HIP system that…

Cryptography and Security · Computer Science 2011-09-02 Sushma Yalamanchili , M. Kameswara Rao

In this paper we study the suitability of a new generation of CAPTCHA methods based on smartphone interactions. The heterogeneous flow of data generated during the interaction with the smartphones can be used to model human behavior when…

Cryptography and Security · Computer Science 2020-10-07 Alejandro Acien , Aythami Morales , Julian Fierrez , Ruben Vera-Rodriguez , Oscar Delgado-Mohatar

We propose a new scheme of attack on the Microsoft's ASIRRA CAPTCHA which represents a significant shortcut to the intended attacking path, as it is not based in any advance in the state of the art on the field of image recognition. After…

Cryptography and Security · Computer Science 2009-08-11 Carlos Javier Hernandez-Castro , Arturo Ribagorda , Yago Saez

Since about 2003, captchas have been widely used as a barrier against bots, while simultaneously annoying great multitudes of users worldwide. As their use grew, techniques to defeat or bypass captchas kept improving, while captchas…

Cryptography and Security · Computer Science 2023-11-23 Andrew Searles , Renascence Tarafder Prapty , Gene Tsudik

Deep learning technology has made it possible to generate realistic content of specific individuals. These `deepfakes' can now be generated in real-time which enables attackers to impersonate people over audio and video calls. Moreover,…

Cryptography and Security · Computer Science 2023-01-10 Lior Yasur , Guy Frankovits , Fred M. Grabovski , Yisroel Mirsky

The rapid evolution of GUI-enabled agents has rendered traditional CAPTCHAs obsolete. While previous benchmarks like OpenCaptchaWorld established a baseline for evaluating multimodal agents, recent advancements in reasoning-heavy models,…

Machine Learning · Computer Science 2026-02-10 Jiacheng Liu , Yaxin Luo , Jiacheng Cui , Xinyi Shang , Xiaohan Zhao , Zhiqiang Shen

Preservation of information and computer security is broadly dependent on the secured authentication system which is underpinned by password. Text based password is a commonly used and available system for authentication. But it bears many…

Cryptography and Security · Computer Science 2022-05-26 Sanjida Akter Sharna , Sheikh Ashraf Ali

Password users frequently employ passwords that are too simple, or they just reuse passwords for multiple websites. A common complaint is that utilizing secure passwords is too difficult. One possible solution to this problem is to use a…

Cryptography and Security · Computer Science 2019-06-04 Elan Rosenfeld , Santosh Vempala , Manuel Blum

As a widely deployed security scheme, text-based CAPTCHAs have become more and more difficult to resist machine learning-based attacks. So far, many researchers have conducted attacking research on text-based CAPTCHAs deployed by different…

Computer Vision and Pattern Recognition · Computer Science 2020-08-27 Chunhui Li , Xingshu Chen , Haizhou Wang , Yu Zhang , Peiming Wang

CAPTCHAs are a defense mechanism to prevent malicious bot programs from abusing websites on the Internet. hCaptcha is a relatively new but emerging image CAPTCHA service. This paper presents an automated system that can break hCaptcha…

Cryptography and Security · Computer Science 2022-03-08 Md Imran Hossen , Xiali Hei

The trend toward a highly mobile workforce and the ubiquity of graphical interfaces (such as the stylus and touch-screen) has enabled the emergence of graphical authentications in Personal Digital Assistants (PDAs) [1]. However, most of the…

Cryptography and Security · Computer Science 2013-06-03 Xiyang Liu , Zhongjie Ren , Xiuling Chang , Haichang Gao , Uwe Aickelin

Nowadays, user authentication is one of the important topics in information security. Strong textbased password schemes could provide with certain degree of security. However, the fact that strong passwords are difficult to memorize often…

Cryptography and Security · Computer Science 2009-12-08 Farnaz Towhidi , Maslin Masrom

Passwords provide security mechanism for authentication and protection services against unwanted access to resources. A graphical based password is one promising alternatives of textual passwords. According to human psychology, humans are…

Cryptography and Security · Computer Science 2011-10-19 Wazir Zada Khan , Mohammed Y. Aalsalem , Yang Xiang

CAPTCHAs/HIPs are security mechanisms that try to prevent automatic abuse of services. They are susceptible to learning attacks in which attackers can use them as oracles. Kwon and Cha presented recently a novel algorithm that intends to…

Cryptography and Security · Computer Science 2017-02-14 Carlos Javier Hernández-Castro , María D. R-Moreno , David F. Barrero , Shujun Li

Nowadays, CAPTCHAs are computer generated tests that human can pass but current computer systems can not. They have common usage in various web services in order to be able to detect a human from computer programs autonomously. In this way,…

Machine Learning · Computer Science 2019-01-09 Ahmet Faruk Cakmak , Muhammet Balcilar