The captcha is used to differentiate between people and machines.
Captcha is an acronym that corresponds to the English expression “Completely Automated Public Turing test to tell Computers and Humans Apart” . This phrase refers to a Turing test that is carried out publicly and automated with the aim of differentiating people from computers (computers).
To understand what a captcha is, therefore, we must know what the Turing test consists of. This test is developed with the objective of distinguishing, in an exchange of messages, a machine from a human being . In the Turing test , an individual controls the test; In captcha, on the other hand, a machine manages the entire process. That is why it is said that the captcha is a Turing test carried out in reverse, since a computer executes it to discover if the person participating is another machine or a person.
captcha features
The captcha consists of a test that generally forces the user to enter a series of characters that appear in a distorted image . This test is based on the inability of machines to recognize deformed characters. Therefore, the one who successfully completes the captcha is a human being.
Since this recognition system has been around for quite some time, over the years it has taken various forms, many of which no longer require text entry. On some sites, a box is shown with several images and the user is instructed to select some of them, giving them a well-defined criterion; For example, they may be photographs of public roads, of which you only have to click on those in which you can see a traffic light.
This system is used on websites to prevent unwanted messages or certain actions carried out automatically by a machine. On many sites it is necessary to pass a captcha to post a comment: this prevents massive advertising distributed by computer programs.
His shortcomings
Beyond its effectiveness, the captcha has several shortcomings. A human with a visual impairment , for example, might have trouble recognizing the characters and passing the test .
Although in general terms we associate the concept of captcha with the fight against piracy and computer attacks, this system is also used by those who practice illegal activities, even if they do not do so directly. For example, people who distribute movies, books, music and video games for free often seek monetary income through companies that provide them with a system that forces the user to watch certain advertisements before accessing the content and, finally, to pass a captcha.
Recaptcha is an extension of captcha that is used to recognize text in images.
The recaptcha
On the other hand is recaptcha , sometimes written reCAPTCHA , an extension of captcha that is also used for text recognition in images. The main difference between both applications of the test is that in this case the text sources are books or documents of great value that have not yet been digitized and archived in libraries, and the user's work is used for this same purpose. In short, recaptcha allows us to reduce the percentage of virtual fraud while enriching cultural heritage.
The concept of recaptcha arose based on the fact that text in an image that, for a computer, can be very difficult to understand, can be very easy to read for a human being. In other words, thanks to this movement, the text digitization process is considerably accelerated, while recognition technology continues to advance slowly until it reaches the level where human labor can be completely dispensed with.