With the development of the Internet and the increase in the number of automatic programs and robots capable of performing various tasks, it became necessary to create mechanisms for separating people from computer agents. One of such mechanisms, which has found wide application, is called captcha.
Captcha (Completely Automated Public Turing test to tell Computers and Humans Apart) is a verification system used to determine whether a user is a human or a computer program.
The first captcha was proposed in 1997 by Louis von Ahn, Adam Biatta and Manuel Blum at Carnegie Mellon University. They developed a method known as the "image-based Turing test", where the user was asked to recognize and enter symbols presented in a distorted picture.
This simple test made it possible to distinguish computer bots from people, since it was difficult for the programs to correctly recognize symbols on a distorted picture. The first captcha was a step forward in security and prevention of automatic generation and sending of spam.
With the passage of time and the development of technologies, various types of captchas appeared. Here are some of them:
1. Text captcha: This is the most common type of captcha, which requires the user to enter characters presented as text. Initially, these symbols were simple and clear, but with the development of algorithms for text recognition by artificial intelligence, the symbols became increasingly complex and distorted to complicate the task of recognition by computer programs.
2. Audio captcha: This type of captcha is used for users who have vision problems or to increase security. Here, the user is offered to listen to audio recordings and enter words or numbers that were pronounced in the audio file. Audio captcha provides an alternative to the text form and provides access to content for users with limited capabilities.
3. Mathematical captcha: This type of captcha requires the user to solve a simple mathematical equation or perform another mathematical operation. For example, the user may be shown two numbers, and he must enter their sum or product. This type of captcha is easy for people to use, but more difficult for computer programs to recognize.
4. Geometric captcha: In this type of captcha, the user is offered to select certain geometric figures, for example, to mark all the squares or triangles in the image. This helps to distinguish people from computer programs, which have difficulties with recognition and classification of geometric figures.
5. Interactive captcha: This type of captcha requires the user to perform a specific action or interact with elements on the page. For example, the user may be asked to drag an object to a certain area or to solve a puzzle. This is more difficult for automatic programs, as it requires the understanding and execution of complex tasks that are easily performed by humans.
Over time, captchas continue to develop, algorithms become more complex, and methods of text and image recognition are improved. However, the development of computer programs does not stand still, and therefore captchas are constantly trying to improve and create new methods for distinguishing people from computers.
Captchas play an important role in Internet security, spam prevention, and protection against automated attacks. They help create a barrier between people and computer programs, ensuring safer and more reliable interaction with web services and online platforms.
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