Definition of Captcha
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 in a public and
automated way with the objective of differentiating people from computers
(computers).
To
understand what a captcha is, therefore, we must know what the Turingtestconsists
of . This
test is developed with the objective of distinguishing, in an exchange of
messages, a machine of a human being . In the Turing test ,
an individual controls the test; In the 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 the opposite direction, since
a computer runs it to find out if the participant is another machine or a
person. The captcha
consists of a testthat usually forces the user to enter a series of
charactersthat appear in a distorted image.This test is based
on the inability of
machines to recognize deformed characters. Therefore,
the one who manages to complete the captcha successfully is a human being.
Since this
system of recognition exists for quite some time, over the years it
has been taking various forms, many of which no longer require the entry of
text. In some sites a box with several images is shown and the user is
instructed to select some of them, giving it a well-defined criterion; for
example, it may be photographs of the public road which you only have to click
on those in which you see a traffic light.
This system is
used on websites to avoid unwanted messages or certain actions
performed automatically by a machine. In many sites it is necessary to
overcome a captcha to post a comment: this prevents mass advertising
distributed through computer programs. Beyond its
effectiveness, the captcha presents several flaws.
A human with a visual
impairment , for example, may 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, although they do not do it
directly. For example, people who distribute movies, books, music and
video games for free usually seek a monetary income
through companies that
provide them with a system that forces the user to look at
certain advertisements before accessing the content and, finally,to over comea captcha .
On the other
hand is the recaptcha , sometimes written reCAPTCHA , an
extension of the captcha that is also used for the recognition of
text 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, the recaptcha allows
reducing the percentage of virtual frauds while enriching the cultural
heritage.
The concept
of recaptcha arose based on the fact that a text in an image that
for a computer can be very difficult to understand, for a human being can be
very easy to read. In other words, thanks to this movement, the process of
digitizing texts is considerably accelerated, while the recognition technology
continues to advance slowly until reaching the level to be able to completely
dispense with human work.
