Full Form of CAPTCHA:
Completely Automated Public Turing test to tell Computers and Humans Apart
CAPTCHA Full Form is Completely Automated Public Turing test to tell Computers and Humans Apart. CAPTCHA is a kind of challenge-response test that is used in computing services for the determination of whether or not a particular user is a human. The term was first used by Manuel Blum, Luis von Ahn, John Langford and Nicholas J. Hopper. The most common kind of CAPTCHA was developed in the year 1997 by two groups engaged in parallel in which the first group comprised Krishna Bharat, Martin Abadi, and Andrei Z. Broder and the second group comprised Raanan, Solan, and Reshef.
The form of CAPTCHA these groups developed required that a user type letters contained in a distorted image, often with the incorporation of an obscured sequence of digits or letters appearing on the screen. The fact that the test is conducted by a computer instead of human (as in a standard Turing Test), a CAPTCHA is often referred to as a reverse Turing test. This test has garnered a lot of criticisms, particularly from disabled persons. Most of the criticism relates to the difficulty in comprehending the letters contained in the distorted image. On an average, a person takes in the neighbourhood of 10 seconds to solve a CAPTCHA.
CAPTCHA are vulnerable to many circumventing attempts which have exceedingly reduced the credibility of CAPTCHA. There are cheap methods that easily crack a CAPTCHA code automatically such as unwitting human labour, in which human operators are employed to solve CAPTCHAs; insecure implementation as in bypassing of CAPTCHA protection mechanisms by re-utilising the session ID of an identified CAPTCHA image. Thus, despite the notable aim with which the procedure was established, there are numerous major issues relating to the credence of the same.