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CAPTCHAs are widely used by websites to block bots and spam by presenting challenges that are easy for humans but difficult for automated programs to solve. To improve accessibility, audio CAPTCHAs are designed to complement visual ones.…

Sound · Computer Science 2026-01-14 Ziqi Ding , Yunfeng Wan , Wei Song , Yi Liu , Gelei Deng , Nan Sun , Huadong Mo , Jingling Xue , Shidong Pan , Yuekang Li

Over the last years, most websites on which users can register (e.g., email providers and social networks) adopted CAPTCHAs (Completely Automated Public Turing test to tell Computers and Humans Apart) as a countermeasure against automated…

Human-Computer Interaction · Computer Science 2015-12-18 Mauro Conti , Claudio Guarisco , Riccardo Spolaor

Object detection systems using deep learning models have become increasingly popular in robotics thanks to the rising power of CPUs and GPUs in embedded systems. However, these models are susceptible to adversarial attacks. While some…

Robotics · Computer Science 2024-07-12 Han Wu , Sareh Rowlands , Johan Wahlstrom

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

A secure human identification protocol aims at authenticating human users to a remote server when even the users' inputs are not hidden from an adversary. Recently, the authors proposed a human identification protocol in the RSA Conference…

Cryptography and Security · Computer Science 2007-05-23 Hassan Jameel , Heejo Lee , Sungyoung Lee

Machine learning models are known to be vulnerable to adversarial attacks, but traditional attacks have mostly focused on single-modalities. With the rise of large multi-modal models (LMMs) like CLIP, which combine vision and language…

Machine Learning · Computer Science 2024-10-18 Arka Daw , Megan Hong-Thanh Chung , Maria Mahbub , Amir Sadovnik

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

Universal Circuits (UCs) offer a promising approach to hardware Intellectual Property (IP) obfuscation, leveraging cryptographic principles to hide both structure and function in a programmable logic fabric. Their adaptability makes them…

Cryptography and Security · Computer Science 2026-04-07 Zain Ul Abideen , Deepali Garg , Lawrence Pileggi , Samuel Pagliarini

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

In a zero-trust fabless paradigm, designers are increasingly concerned about hardware-based attacks on the semiconductor supply chain. Logic locking is a design-for-trust method that adds extra key-controlled gates in the circuits to…

Cryptography and Security · Computer Science 2024-02-07 Yeganeh Aghamohammadi , Amin Rezaei

Backdoor attacks pose a serious threat to deep learning models by allowing adversaries to implant hidden behaviors that remain dormant on clean inputs but are maliciously triggered at inference. Existing backdoor attack methods typically…

Cryptography and Security · Computer Science 2025-11-18 Lijie Hu , Junchi Liao , Weimin Lyu , Shaopeng Fu , Tianhao Huang , Shu Yang , Guimin Hu , Di Wang

Optical Character Recognition (OCR) is a widely used tool to extract text from scanned documents. Today, the state-of-the-art is achieved by exploiting deep neural networks. However, the cost of this performance is paid at the price of…

Cryptography and Security · Computer Science 2023-10-13 Mauro Conti , Nicola Farronato , Stefanos Koffas , Luca Pajola , Stjepan Picek

CAPTCHAs are commonly used to distinguish between human and bot users on the web. However, despite having various types of CAPTCHAs, there are still concerns about their security and usability. To address these concerns, we surveyed over…

Cryptography and Security · Computer Science 2024-05-30 Arun Reddy , Yuan Cheng

Existing work in trustworthy machine learning primarily focuses on single-input adversarial perturbations. In many real-world attack scenarios, input-agnostic adversarial attacks, e.g. universal adversarial perturbations (UAPs), are much…

Machine Learning · Computer Science 2024-09-10 Changming Xu , Gagandeep Singh

A cyber-attack is a malicious attempt by experienced hackers to breach the target information system. Usually, the cyber-attacks are characterized as hybrid TTPs (Tactics, Techniques, and Procedures) and long-term adversarial behaviors,…

Cryptography and Security · Computer Science 2021-12-17 Mingqi Lv , Chengyu Dong , Tieming Chen , Tiantian Zhu , Qijie Song , Yuan Fan

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

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

Adversarial attacks pose a critical security threat to real-world AI systems by injecting human-imperceptible perturbations into benign samples to induce misclassification in deep learning models. While existing detection methods, such as…

Computer Vision and Pattern Recognition · Computer Science 2025-04-02 Yinghe Zhang , Chi Liu , Shuai Zhou , Sheng Shen , Peng Gui

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

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