English
Related papers

Related papers: User Friendly Line CAPTCHAs

200 papers

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

Reliable human-machine discrimination is becoming increasingly important as large language models and autonomous agents are deployed in online settings. Existing approaches evaluate whether a system can produce behavior or responses…

Artificial Intelligence · Computer Science 2026-05-12 Milena Rmus , Mathew D. Hardy , Thomas L. Griffiths , Mayank Agrawal

With the growth of connectivity to smart grids, new applications, and the changing interaction between customer and energy clouds, clouds are more vulnerable to denial-of-service attacks. Efficient detection methods are required to…

Cryptography and Security · Computer Science 2020-04-10 Monther Aldwairi , Suaad Mohammed , Megana Lakshmi Padmanabhan

We propose an alternative to the Turing test that removes the inherent asymmetry between humans and machines in Turing's original imitation game. In this new test, both humans and machines judge each other. We argue that this makes the test…

Artificial Intelligence · Computer Science 2022-05-12 Toby Walsh

CAPTCHAs have long been essential tools for protecting applications from automated bots. Initially designed as simple questions to distinguish humans from bots, they have become increasingly complex to keep pace with the proliferation of…

Cryptography and Security · Computer Science 2025-02-25 Ziqi Ding , Gelei Deng , Yi Liu , Junchen Ding , Jieshan Chen , Yulei Sui , Yuekang Li

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

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 short note, we propose a unified framework that bridges three areas: (1) a flipped perspective on the Turing Test, the "dual Turing test", in which a human judge's goal is to identify an AI rather than reward a machine for…

Machine Learning · Computer Science 2025-07-23 Alberto Messina

We introduce Reverse CAPTCHA, an evaluation framework that tests whether large language models follow invisible Unicode-encoded instructions embedded in otherwise normal-looking text. Unlike traditional CAPTCHAs that distinguish humans from…

Cryptography and Security · Computer Science 2026-03-03 Marcus Graves

To this date, CAPTCHAs have served as the first line of defense preventing unauthorized access by (malicious) bots to web-based services, while at the same time maintaining a trouble-free experience for human visitors. However, recent work…

Cryptography and Security · Computer Science 2020-11-05 Dorjan Hitaj , Briland Hitaj , Sushil Jajodia , Luigi V. Mancini

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

We introduce GOTCHAs (Generating panOptic Turing Tests to Tell Computers and Humans Apart) as a way of preventing automated offline dictionary attacks against user selected passwords. A GOTCHA is a randomized puzzle generation protocol,…

Cryptography and Security · Computer Science 2013-10-07 Jeremiah Blocki , Manuel Blum , Anupam Datta

Large language models (LLMs) are increasingly used in the social sciences to simulate human behavior, based on the assumption that they can generate realistic, human-like text. Yet this assumption remains largely untested. Existing…

Computation and Language · Computer Science 2025-11-26 Nicolò Pagan , Petter Törnberg , Christopher A. Bail , Anikó Hannák , Christopher Barrie

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

Following the principle of to set one's own spear against one's own shield, we study how to design adversarial CAPTCHAs in this paper. We first identify the similarity and difference between adversarial CAPTCHA generation and existing hot…

Cryptography and Security · Computer Science 2019-01-07 Chenghui Shi , Xiaogang Xu , Shouling Ji , Kai Bu , Jianhai Chen , Raheem Beyah , Ting Wang

Handwriting movements can be leveraged as a unique form of behavioral biometrics, to verify whether a real user is operating a device or application. This task can be framed as a reverse Turing test in which a computer has to detect if an…

Computer Vision and Pattern Recognition · Computer Science 2026-01-21 Luis A. Leiva , Moises Diaz , Nuwan T. Attygalle , Miguel A. Ferrer , Rejean Plamondon

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

Text CAPTCHA has been an effective means to protect online systems from spams and abuses caused by automatic scripts which pretend to be human beings. However, nearly all the Text CAPTCHA designs in nowadays are based on English characters,…

Human-Computer Interaction · Computer Science 2016-12-06 Junnan Yu , Xuna Ma , Ting Han

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

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