While confirming any activity or action on a website or a web application, we are often asked to enter some alphanumerical characters, presented on the screen, which is known as “captcha“. But the big question is why do we need to enter this captcha everytime to confirm certain actions on web? What is the significance of captcha? Why is it considered to be very important?
With the advancement in the field of artificial intelligence, machines are being made up to perform the same action, which a normal human does.They are being designed with an ability to exhibit intelligent behavior equivalent to, or indistinguishable from, that of a human. Now with the makings of such machines that exhibits human behavior, a situation may arise where it may become difficult to distinguish between a human and a machine. You may not know that the person on the other side of the wall with whom you are in a conversation is really a human, or a machine with its own artificial intelligence exhibiting a human behavior.
The Turing test, developed by Alan Turing in 1950, is a solution to such problems up to certain extent. It is a test for intelligence in a computer, requiring that a human being should be unable to distinguish the machine from another human being by using the answers in replies to questions put to both. It is like one interrogator has been assigned to identify among two bodies which of them is a machine and which is a human, by putting up a list of questions. If the interrogator cannot reliably tell the machine from the human, the machine is said to have passed the test. Since we know that it is really impossible to predict human answers, the test however does not check the ability to give correct answers to questions, only how closely answers resemble those a human would give.
The most common Turing test we come across very often is “Captcha”. It is a form of reverse Turing test. Captcha is a backronym for “Completely Automated Public Turing test to tell Computers and Humans Apart”. Before being allowed to perform some action on a website, the user is presented with alphanumerical characters in a distorted graphic image and asked to type them out. This is basically done to prevent automated systems from being used to abuse the site. The basic logic is that software sufficiently sophisticated to read and reproduce the distorted image accurately does not exist (or is not available to the average user), so any system able to do so is likely to be a human as the chances of any machine to solve it is very low. Captcha, being a Turing test, is considered as a benchmark task for artificial intelligence technologies.
According to an article by Ahn, Blum and Langford,
“Any program that passes the tests generated by a Captcha can be used to solve a hard unsolved AI problem.”