What is a recaptcha ? How it works ?

What is a Captcha ?

A Captcha is an acronym for "Completely Automated Public Turing Test to tell Computers and Humans Apart". It is a type of verification for a normal user that he is a human not a bot or automated computer system . 

 A reCaptcha is a Captcha like system designed to establish that a computer user is a human or a automated bot .The system has been reported as displaying over 100 million Captchas every day, on sites such as a Facebook , Twitter , CNN.com .

Its slogan was " STOP SPAM READ BOOKS ". After the introduction to new version of reCaptcha in 2014 , the slogan is now " EASY ON HUMANS , HARD ON BOTS ". A new system featuring image verification was also introduced. In this system, users are asked to just click on a checkbox (the system will verify whether the user is a human or not).

The term was introduced in 2003 by Luis von Ahn , Manuel Blum , Nicholas J. hopper and John langford. The most common type of CAPTCHA (displayed as Version 1.0) was first invented in 1997 by two groups working in parallel .This form of CAPTCHA requires someone to correctly evaluate and enter a sequence of letters in a distorted or mixed image displayed on their screen. This method was good but not perfect in order to save time because every person was complaining about its time consumption . It takes 10 seconds to solve a normal captcha.

HISTORY

^{In earlier days of Internet , user wanted to make text illegible or non-understandable to computers . Those people were Hackers .To circumvent such filters, they replaced a word with a look alike characters .HI will become [ |-|; ] , as well as other variants like such that a filter could not detect all of them . This later became LEETSPEAK.}

^{A popular deployment of CAPTCHA technology, reCaptcha, was acquired by Google in 2009. In addition to preventing bot fraud for its users, Google used reCAPTCHA and CAPTCHA technology to digitize the archives of The New York Times and books from Google Books in 2011.}

^WORKING 

^{The working of a reCaptcha is very interesting and logical . In the reCaptcha v3, their is no need to type distorted texts . It automatically responses toward the bots or the humans .So how is it even possible  ?}

^{It is possible with a great technology used by GOOGLE . The logic behind the reCaptcha v3 was to circumvent typing and saving time of the users . So Google is recognising the mouse movement of a user  right before signing the reCaptcha . This is because the humans tend to move their mouse in an imperfect way . But the bot is considered by its stability of mouse . The humans can't be that fluent and clear .}

Human controlling mouse

   ^{A very good example shown in this picture. It is shown that when humans tend to move their mouse they just get imperfect or imbalanced from their path as show in the picture. It shows that the user is a human}

 

Bot controlling mouse

  ^{A very good example is shown in this picture of}

 ^{a bot controlling a mouse . It is shown in the picture that the bot is controlling the mouse in very perfect and balanced way so that it is not moving or distracting from its path . It clearly shows that it is a bot .}

 ^{Another way to find bots is checking cookies activities . Google checks the cookies for checking whether a user is a human or a bot . Google provided this facility to render humans and bots entries in a system . The mouse movement is checked before the Captcha is clicked so the Google's algorithm checks the user whether he is a human or a bot .}