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In this paper the elements of the CAPTCHA usability are analyzed. CAPTCHA, as a time progressive element in computer science, has been under constant interest of ordinary, professional as well as the scientific users of the Internet. The…

Human-Computer Interaction · Computer Science 2017-07-03 Darko Brodić , Alessia Amelio , Ivo R. Draganov

CAPTCHAs are employed as a security measure to differentiate human users from bots. A new sound-based CAPTCHA is proposed in this paper, which exploits the gaps between human voice and synthetic voice rather than relays on the auditory…

Cryptography and Security · Computer Science 2013-06-13 Haichang Gao , Honggang Liu , Dan Yao , Xiyang Liu , Uwe Aickelin

CAPTCHA is a human-centred test to distinguish a human operator from bots, attacking programs, or other computerised agents that tries to imitate human intelligence. In this research, we investigate a way to crack visual CAPTCHA tests by an…

Computer Vision and Pattern Recognition · Computer Science 2020-06-26 Zahra Noury , Mahdi Rezaei

CAPTCHAs are widely employed for distinguishing humans from automated bots online. However, current vision based CAPTCHAs face escalating security risks: traditional attacks continue to bypass many deployed CAPTCHA schemes, and recent…

Computers and Society · Computer Science 2025-12-19 Ziqi Ding , Shangzhi Xu , Wei Song , Yuekang Li

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

CAPTCHA(Completely Automated Public Turing test to Tell Computers and Humans Apart) can be used to protect data from auto bots. Countless kinds of CAPTCHAs are thus designed, while we most frequently utilize text-based scheme because of…

Computer Vision and Pattern Recognition · Computer Science 2018-06-20 Ye Wang , Mi Lu

Online services commonly attempt to verify the legitimacy of users with CAPTCHAs. However, CAPTCHAs are annoying for users, often difficult for users to solve, and can be defeated using cheap labor or, increasingly, with improved…

Cryptography and Security · Computer Science 2017-11-07 Ben Doyle , Patrick Korth , Kyle Nekritz , Zane Salem

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

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

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

A recent study has found that malicious bots generated nearly a quarter of overall website traffic in 2019 [100]. These malicious bots perform activities such as price and content scraping, account creation and takeover, credit card fraud,…

Cryptography and Security · Computer Science 2022-01-25 Meriem Guerar , Luca Verderame , Mauro Migliardi , Francesco Palmieri , Alessio Merlo

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

Crowdsourcing human-solving or online typing attacks are destructive problems. However, studies into these topics have been limited. In this paper, we focus on this kind of attacks whereby all the CAPTCHAs can be simply broken because of…

Cryptography and Security · Computer Science 2019-04-30 Jianyi Zhang , Xiali Hei , Zhiqiang Wang

For a number of years, many websites have used CAPTCHAs to filter out interactions by bots. However, attackers have found ways to circumvent CAPTCHAs by programming bots to solve or bypass them, or even relay them for humans to solve. In…

Cryptography and Security · Computer Science 2017-04-11 Nasser Mohammed Al-Fannah

CAPTCHAs are designed to prevent malicious bot programs from abusing websites. Most online service providers deploy audio CAPTCHAs as an alternative to text and image CAPTCHAs for visually impaired users. However, prior research…

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

Mobile devices store a diverse set of private user data and have gradually become a hub to control users' other personal Internet-of-Things devices. Access control on mobile devices is therefore highly important. The widely accepted…

Cryptography and Security · Computer Science 2019-11-26 Neil Zhenqiang Gong , Mathias Payer , Reza Moazzezi , Mario Frank

Online services rely on CAPTCHAs as a first line of defense against automated abuse, yet recent advances in multi-modal large language models (MLLMs) have eroded the effectiveness of conventional designs that focus on text recognition or 2D…

Artificial Intelligence · Computer Science 2025-10-07 Arina Kharlamova , Bowei He , Chen Ma , Xue Liu

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

Smart mobile devices have become indispensable in modern daily life, where sensitive information is frequently processed, stored, and transmitted-posing critical demands for robust security controls. Given that touchscreens are the primary…

Cryptography and Security · Computer Science 2025-04-25 Mengyu Qiao , Yunpeng Zhai , Yang Wang

Completely Automated Public Turing tests to tell Computers and Humans Apart (CAPTCHAs) are a foundational component of web security, yet traditional implementations suffer from a trade-off between usability and resilience against AI-powered…

Cryptography and Security · Computer Science 2025-10-06 Ayda Aghaei Nia