Understanding Captcha: Text and Audio Based Captcha with its Applications (original) (raw)
Related papers
CAPTCHA: A SECURITY MEASURE AGAINST SPAM ATTACKS
A CAPTCHA is challenge response test used to ensure that the response is generated by humans. CAPTCHA test are administrator by machines to differentiate between humans and machine. Because of this reason CAPTCHAs are also known as the Reverse Turing Test as contrast to Turing Test which is administrated by humans.
Technique to CAPTCHA Recognition
Abstract: A CAPTCHA is a program that can generate and grade tests that humans can pass but current computer programs cannot. For example, humans can read distorted text as the one shown below, but current computer programs can't. The term CAPTCHA (for Completely Automated Turing Test to Tell Computers and Humans Apart) was coined in 2000 by Luis von Ahn, Manuel Blum, Nicholas Hopper and John Langford of Carnegie Mellon University. At the time, they developed the first CAPTCHA to be used by Yahoo. ReCAPTCHA improves the process of digitizing books by sending words that cannot be read by computers to the Web in the form of CAPTCHAs for humans to decipher. More specifically, each word that cannot be read correctly by OCR is placed on an image and used as a CAPTCHA. This is possible because most OCR programs alert you when a word cannot be read correctly. Keyword: CAPTCHA, automated, digitizing, decipher, OCR. Title: Technique to CAPTCHA Recognition Author: Prof.G.K.Gaikwad, Prof.B.S.Chaudhary International Journal of Computer Science and Information Technology Research ISSN 2348-120X (online), ISSN 2348-1196 (print) Research publish Journals
Is it human or computer? Defending e-commerce with Captchas
IT Professional, 2005
Captcha-a completely automatic public Turing test to tell computers and humans apart-is a test that humans can pass but computer programs cannot; such tests are becoming key to defending ecommerce systems.Without them, spammers can, for example, write simple automated scripts to create hundreds of free e-mail accounts with a single command. The e-mail service provider can choose not to validate the information supplied by uses, but ends up with thousands of useless accounts. On the other hand, the provider can assume the extra burden of validating this information, but risks crippling its systems with the extra burden that validation requires. By inserting a Captcha into the login and user creation process, system administrators can defeat these automated scripts and have some assurance that an actual human is associated with the account. Similarly, Captchas are also useful in defending online shopping or auction sites by preventing spammers from posting irrelevant or bogus bids to prevent other buyers from purchasing products. Captchas are a modern implementation of the Turing test, which asks a series of questions of two players: a computer and a human. Both players pretend to be human and try to mislead the judge. Based on the answers given, the judge has to decide which one is human and which is a computer. Captchas are similar to the Turing test in that they distinguish computers from humans, except that, with a Captcha, the judge is also a computer. Captchas also differ from the Turing test because they work on a variety of sensory inputs, whereas the Turing test is conversational. Captchas come in several different types. Most generally, the Captcha is simply an image composed of pseudorandom letters and numbers placed either in front of an obfuscating background or run through some degradation algorithm to make optical character recognition (OCR) of the final image impractical. HISTORY AltaVista was the first to use a simple Captcha that generated images of random text. It used the Captcha to prevent users from abusing its free-URL submission utility.Andrei Broder,AltaVista chief scientist, and his colleagues patented the technology in 2001. The AltaVista Captcha reduced abuse by 95 percent (http://msdn. microsoft.com/library/default.asp?url=/library/ en-us/dnaspp/html/hip_aspnet.asp). In 2000, Udi Mamber of Yahoo was looking for ways to prevent bots from joining the online chat rooms to post advertisements. Researchers at Carnegie Mellon University took up the problem and proceeded to quantify desirable characteristics of Captchas as well as generate several types, including the Gimpy type described later. The Xerox Palo Alto Research Center (PARC) also actively continues to study Captchas. PARC researchers have most recently developed Baffle Captchas can provide an easily programmable way to tell computers from humans and keep spammers and bots away from e-commerce systems.
A Study on CAPTCHA Techniques & It's Applications
Captcha is an acronym for (Completely Automated public Turing test to tell Computers and Humans Apart) system is used to verify whether a user is human or computer program [1]. It's also known as human Interactive Proof (HIP) and based upon Artificial Intelligence. Now a day's for web security we are using different type of captcha. Captcha is a program that protect websites from web-bots by generate tests that computer cannot pass but person can pass.
On the necessity of user-friendly CAPTCHA
2011
A "Completely Automated Public Turing test to tell Computers and Humans Apart" (CAPTCHA) is a mechanism widely used nowadays for protection of web applications, interfaces, and services from malicious users. A questionnaire-based survey combined with a real usage scenario of a native-language CAPTCHA mechanism was conducted in order to investigate several aspects that affect end-user perceptions related to the quality of CAPTCHA. A total of 210 participants of age between 19 and 64 participated during May and July 2010. The survey results validate the common belief that CAPTCHAs are still difficult for humans to solve. They also provide insights that can be applied to improve users" experience on interacting with CAPTCHA systems.
Text-based CAPTCHAs over the years
IOP Conference Series: Materials Science and Engineering
The notion of CAPTCHAs has been around for more than two decades. Since its introduction, CAPTCHAs have now become a ubiquitous part of the Internet. Over the years, research on various aspects of CAPTCHAs has evolved and different design principles have emerged. This article discusses text-based CAPTCHAs in terms of their fundamental requirements, namely, security and usability. Practicality necessitates that humans must be able to correctly solve CAPTCHA challenges, while at the same time automated computer programs should have difficulty solving the challenges. This article also presents alternative paradigms to text-based CAPTCHA design that have been examined in previous work. With the advances in techniques to defeat CAPTCHAs, the future of automated Turing tests is an open question.
A comprehensive Study for Different Types of CAPTCHA Methods and Various Attacks
Journal of emerging technologies and innovative research, 2021
Due to the growth of the internet in our life and its importance in all our everyday activities , including occupational and educational ones .We should also keep in mind that it harbours a negative aspect , as it brings security problems. Hence CAPTCHAs are used for making systems more secure. The major role of CAPTCHA is to prevent robotic bot (spam) form surrender or prove user personality. Using a pattern-matching algorithm is necessary for the user for comparison by receiving signs founded in similar matches. This method makes it difficult to get a forbidden access to data, since malicious bot is to spy out signs in the image. This mechanism implements actions on the attitude of user gesticulation which makes it distinguishable and secure. Human-Computer Interaction i.e. interaction between computer and individual is made to make it easy in understand human language .On other words, Human-computer Interaction focuses on the study of interfaces between computer and human. This paper presents a comprehensive study of various different types of CAPTCHA, the ones good in securing webpages. It also discusses the strengths and weaknesses of each one. Moreover, its importance in discerning the user's individuality, the behavior of humans, and bots and the paper will illustrate some CAPTCHAs mechaniits and impairments which allows hackers to break .In addition, is necessary to take into consideration the approaches of building a good CAPTCHA.
CAPTCHA is a completely automated program designed to distinguish whether the user is a computer or human. As the problems of Internet security are worsening, it is of great significance to do research on CAPTCHA. This article starts from the recognition of CAPTCHAs, then analyses the weaknesses in it-s design and gives corresponding recognition proposals according to various weaknesses, finally offers suggestions related to the improvement of CAPTCHAs.
A Survey on the Different Implemented Captchas
AIRCC Publishing Corporation, 2019
CAPTCHA is almost a standard security technology, and has found widespread application in commercial websites. There are two types: labeling and image based CAPTCHAs. To date, almost all CAPTCHA designs are labeling based. Labeling based CAPTCHAs refer to those that make judgment based on whether the question “what is it?” has been correctly answered. Essentially in Artificial Intelligence (AI), this means judgment depends on whether the new label provided by the user side matches the label already known to the server. Labeling based CAPTCHA designs have some common weaknesses that can be taken advantage of attackers. First, the label set, i.e., the number of classes, is small and fixed. Due to deformation and noise in CAPTCHAs, the classes have to be further reduced to avoid confusion. Second, clean segmentation in current design, in particular character labeling based CAPTCHAs, is feasible. The state of the art of CAPTCHA design suggests that the robustness of character labeling schemes should rely on the difficulty of finding where the character is (segmentation), rather than which character it is (recognition). However, the shapes of alphabet letters and numbers have very limited geometry characteristics that can be used by humans to tell them yet are also easy to be indistinct. Image recognition CAPTCHAs faces many potential problems which have not been fully studied. It is difficult for a small site to acquire a large dictionary of images which an attacker does not have access to and without a means of automatically acquiring new labeled images, an image based challenge does not usually meet the definition of a CAPTCHA. They are either unusable or prone to attacks. In this paper, we present the different types of CAPTCHAs trying to defeat advanced computer programs or bots, discussing the limitations and drawbacks of each.