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CAPTCHAs have become a ubiquitous tool in safeguarding applications from automated bots. Over time, the arms race between CAPTCHA development and evasion techniques has led to increasingly sophisticated and diverse designs. The latest…

Cryptography and Security · Computer Science 2024-05-14 Gelei Deng , Haoran Ou , Yi Liu , Jie Zhang , Tianwei Zhang , Yang Liu

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

Image CAPTCHA, aiming at effectively distinguishing human users from malicious script attacks, has been an important mechanism to protect online systems from spams and abuses. Despite the increasing interests in developing and deploying…

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

Bots constitute a significant portion of Internet traffic and are a source of various issues across multiple domains. Modern bots often become indistinguishable from real users, as they employ similar methods to browse the web, including…

Machine Learning · Computer Science 2024-12-04 Jan Kadel , August See , Ritwik Sinha , Mathias Fischer

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

This paper presents a human verification scheme in two independent stages to overcome the vulnerabilities of attacks and to enhance security. At the first stage, a hand image-based CAPTCHA (HandCAPTCHA) is tested to avert automated…

Computer Vision and Pattern Recognition · Computer Science 2024-10-15 Asish Bera , Debotosh Bhattacharjee , Hubert P H Shum

The advancements in generative AI have enabled the improvement of audio synthesis models, including text-to-speech and voice conversion. This raises concerns about its potential misuse in social manipulation and political interference, as…

Cryptography and Security · Computer Science 2024-09-12 Hong-Hanh Nguyen-Le , Van-Tuan Tran , Dinh-Thuc Nguyen , Nhien-An Le-Khac

Sybil attacks remain a fundamental obstacle in open online systems, where adversaries can cheaply create and sustain large numbers of fake identities. Existing defenses, including CAPTCHAs and one-time proof-of-personhood mechanisms,…

Cryptography and Security · Computer Science 2026-01-08 Homayoun Maleki , Nekane Sainz , Jon Legarda

Benefiting from strong and efficient multi-modal alignment strategies, Large Visual Language Models (LVLMs) are able to simulate human visual and reasoning capabilities, such as solving CAPTCHAs. However, existing benchmarks based on visual…

Artificial Intelligence · Computer Science 2025-12-15 Jianyi Zhang , Ziyin Zhou , Xu Ji , Shizhao Liu , Zhangchi Zhao

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

Convolutional neural networks have been used to achieve a string of successes during recent years, but their lack of interpretability remains a serious issue. Adversarial examples are designed to deliberately fool neural networks into…

Machine Learning · Computer Science 2020-04-28 Jan Philip Göpfert , André Artelt , Heiko Wersing , Barbara Hammer

There has been a rise in the use of Machine Learning as a Service (MLaaS) Vision APIs as they offer multiple services including pre-built models and algorithms, which otherwise take a huge amount of resources if built from scratch. As these…

Computer Vision and Pattern Recognition · Computer Science 2021-05-21 Jaydeep Borkar , Pin-Yu Chen

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

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

Proof of Work (PoW) based cyberdefense systems require incoming network requests to expend effort solving an arbitrary mathematical puzzle. Current state of the art is unable to differentiate between trustworthy and untrustworthy…

Cryptography and Security · Computer Science 2022-03-22 Trisha Chakraborty , Shaswata Mitra , Sudip Mittal , Maxwell Young

The modern pervasiveness of large-scale deep neural networks (NNs) is driven by their extraordinary performance on complex problems but is also plagued by their sudden, unexpected, and often catastrophic failures, particularly on…

Machine Learning · Computer Science 2023-08-02 Sadhana Lolla , Iaroslav Elistratov , Alejandro Perez , Elaheh Ahmadi , Daniela Rus , Alexander Amini

Audio CAPTCHAs are supposed to provide a strong defense for online resources; however, advances in speech-to-text mechanisms have rendered these defenses ineffective. Audio CAPTCHAs cannot simply be abandoned, as they are specifically named…

Metaphors are considered to pose challenges for a wide spectrum of NLP tasks. This gives rise to the area of computational metaphor processing. However, it remains unclear what types of metaphors challenge current state-of-the-art models.…

Computation and Language · Computer Science 2024-01-30 Yucheng Li , Frank Guerin , Chenghua Lin

We study the problem of encrypting and authenticating quantum data in the presence of adversaries making adaptive chosen plaintext and chosen ciphertext queries. Classically, security games use string copying and comparison to detect…

Quantum Physics · Physics 2020-06-17 Gorjan Alagic , Tommaso Gagliardoni , Christian Majenz

Artificial intelligence (AI) has been advancing at a fast pace and it is now poised for deployment in a wide range of applications, such as autonomous systems, medical diagnosis and natural language processing. Early adoption of AI…

Machine Learning · Computer Science 2023-09-21 Marta Kwiatkowska , Xiyue Zhang