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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

This paper introduces an algorithm to protect the privacy of individuals in streaming video data by blurring faces such that face cannot be reliably recognized. This thwarts any possible face recognition, but because all facial details are…

Computer Vision and Pattern Recognition · Computer Science 2019-04-25 Jizhe Zhou , Chi-Man Pun , YingYu Wang

Optical Character Recognition (OCR) has been a topic of interest for many years. It is defined as the process of digitizing a document image into its constituent characters. Despite decades of intense research, developing OCR with…

Computer Vision and Pattern Recognition · Computer Science 2017-10-17 Noman Islam , Zeeshan Islam , Nazia Noor

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

An algorithm for image processing is proposed. The proposed algorithm, which can be viewed as a quantum-classical hybrid algorithm, can transform a low-resolution bitonal image of a character from the set of alphanumeric characters (A-Z,…

Quantum Physics · Physics 2022-12-27 Ankur Pal , Abhishek Shukla , Anirban Pathak

Optical Character Recognition (OCR) has many real world applications. The existing methods normally detect where the characters are, and then recognize the character for each detected location. Thus the accuracy of characters recognition is…

Computer Vision and Pattern Recognition · Computer Science 2020-12-04 Baohua Sun , Michael Lin , Hao Sha , Lin Yang

Gaussian blur is a commonly-used method to filter image data. This paper introduces the collapsing sum, a new operator on matrices that provides a combinatorial interpretation of Gaussian blur. We study the combinatorial properties of this…

Combinatorics · Mathematics 2020-11-18 Travis Dillon

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

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 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

Image data collected in the wild often contains private information such as faces and license plates, and responsible data release must ensure that this information stays hidden. At the same time, released data should retain its usefulness…

Machine Learning · Computer Science 2025-12-19 Saeed Mahloujifar , Narine Kokhlikyan , Chuan Guo , Kamalika Chaudhuri

Gaussian blur is widely used to blur human faces in sensitive photos before the photos are posted on the Internet. However, it is unclear to what extent the blurred faces can be restored and used to re-identify the person, especially under…

Cryptography and Security · Computer Science 2025-06-17 Haoyu Zhai , Shuo Wang , Pirouz Naghavi , Qingying Hao , Gang Wang

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

Biometrics deal with automated methods of identifying a person or verifying the identity of a person based on physiological or behavioral characteristics. Visual cryptography is a secret sharing scheme where a secret image is encrypted into…

Cryptography and Security · Computer Science 2010-04-13 P. S. Revenkar , Anisa Anjum , W. Z. Gandhare

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

Detecting manipulations in digital documents is becoming increasingly important for information verification purposes. Due to the proliferation of image editing software, altering key information in documents has become widely accessible.…

Computer Vision and Pattern Recognition · Computer Science 2023-06-27 Hailey Joren , Otkrist Gupta , Dan Raviv

Protection of faces in pictures and videos of people in connection with sensitive information, activism, abused cases and others on public broadcasting media and social net- works is very important. On social networks like YouTube,facebook,…

Cryptography and Security · Computer Science 2013-07-25 Quist-Aphetsi Kester

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

Warnings have been raised about the steady diminution of privacy. More and more personal information, such as that contained electronic mail, is moving to cloud computing servers where it might be machine-searched and indexed. FauxCrypt is…

Cryptography and Security · Computer Science 2018-02-14 Devlin M. Gualtieri