CAPCHA-RECOGNIZES HUMAN OR MACHINE

WHAT IS CAPCHA?

CAPTCHA is a program that protect and prevent the websites from bots by generating and grading tests that humans can pass but current machines(computer programs) cannot.



The term CAPTCHA refers to Completely Automated Public Turing Test To Tell Computers and Humans Apart.It was firstly formulated by Luis Von Ahn, Manuel Blum, Nicholas Hopper and John Langford of Carnegie Mellon University in 2000. Capcha is also known as one of the type of human interaction proof.In current scenario, we seen capcha code in many websites.User can type the correct code in the form,if your letters match the ones in the distorted image, you pass and redirect on the site.

Why someone need a capcha test ?



Need of the capche test arises because some people trying to play with the system and they want to use the deficiencies of sites for their profits, which can affects the millions of people and the sites .For instance, a free e-mail service can flood itself by account requests from automated programs, which could be part of a big effort to spread spam mail to millions of users. The CAPTCHA test helps in determining who the actual person is and what machines are there.

turning test and types of capchas



Modern computing’s father Allan Turning suggested a test to check whether machines think or not – or think like humans.In this test , an investigator asks to participants a set of problems . One of them is a computer program and the another is a human. Those who take the exam can not see or hear the participants and there is no way to know who is there. If the interrogator is unable to find out which of the reaction is a machine based on the reaction, the machine passes the turning test.



With captcha code, the goal is to prepare a test that a person can easily pass but cannot be machine. It is also important that the CAPTCHA application is capable of offering different caps to different users.



Not all captions are based on visual patterns. In fact, it is important to have a choice for a visual capcha .Otherwise, the Website manager shows the risk of ignoring any web user who has visual disorders.one alternative to a visual test is an audio Captchawhich presents the user with a set of spoken letters or numbers. It’s not unusual for the program to distort the speaker’s voice, and it’s also identified background noise in the recording.



In another type of capcha, user interpret a text to complete the CAPTCHA . While computer programs(machines) can pick out main keywords from the text text , they aren’t very good at recognising what the real meaning of those words .

where capcha is used?

There are many uses for the CAPTCHA’s practical protection-



Occasionally, it is useful to keep web pages temporarily in order to prevent finding others easily.An html tag is available to prevent search engine bots from reading web pages. In spite of that, it does not give surety that bots will not read a web page,it only serves to say “no bots please.”



CAPTCHA provides a rational solution against e-mail worms and spam: “Users will accept only one email if they know that there is a man behind the other computer.” Some companies are already selling this idea.



In November 1999, http://www.slashdot.org issued an online survey, which was the best graduate school in computer science. As with most online surveys, voters’ IP addresses were recorded so that a user could not vote more than once.Still, Carnegie Mellon’s students have thousands of times CUU Found ways to fill the differences while using vote-taking programs. CMU Figures started increasing rapidly The next day MIT students wrote their program and became a contest between poll voting “Boats”. MIT ended with 21,156 votes.Carnegie Malone with 21,032 and other schools less than 1000 Can the result of any online poll be reliable? Unless the election makes sure that only humans can vote.



Spammers crawl the Web to find some email addresses posted in clear text. CAPTCHAs provides an effective solution to hide your email address from Web scrapers.



Most blog programs are familiar with programs that normally make fake comments, for the purpose of increasing the website’s search engine rank, it is known as comment spam. Using CAPTCHA, only humans can post comments on the blog. Before they submit a comment, there is no need to sign up for users, and any diplomatic comments never end.



The number of companies (such as Yahoo!, Microsoft, etc.) offers free e-mail services. Until a few years ago, most of these services suffered from a specific type of attack: “bots” that are up to thousands of email accounts every minute. The solution to this problem was to ensure the use of the Captcha so that only the people could get free accounts.

link with artificial intelligence (ai):



Captcha tests are based on open problems in Artificial intelligence . For example, decoding of images of incorrect text is beyond the capabilities of modern computers. Therefore, CAPTCHA offers good effective challenges for the AI community, and inspires security developers and other dangerous programs to work to advance the AI field. The captcha is thus winning status: either the caption is not broken and the way to separate people from the computer, or the caption is broken and the AI problem is resolved.



In 2006, Von Ahne talked about the relationship between things like Captcha and artificial intelligence (AI). Because the captcha is an obstacle between spam or hacks and their targets, these people have time and energy to break the Captcha. Their successes mean that machines are becoming more complicated. Each time when someone teaches the machine to defeat captcha, we move one step closer to artificial intelligence.



As the spammers or hackers look for new ways around the captcha, technologists such as Von Ahn develop captchas, who address other challenges in AI field.



People who run their websites or online polls need to know that many captive systems are no longer effective. It is important to do some research on which captcha applications are still reliable. And to remain till the date on this subject is equally important. If a captive system fails, the administrator may need to remove the code from your site and it may need to be replaced with another version.



In 2014, Google (which received Recaptcha in 2009) began the work of abolishing the classic service. In place, it asked you to click and tick the box with words “I’m not a robot.” It is not called Captcha, in 2017, Google announced that it was getting rid of the captcha. Instead, this service will depend on the techniques of how you operate an on-the-counter pointers or analyzing your browsing habits that you are a human or robot. It’s called as invisible Recaptcha, if you seem suspicious (you’re actually a robot), you’ll see one of the old recaptcha challenges to be sorted out in more detail.

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