Internet has become a necessity in human life today . With the help of this, many tasks are started to be done easily.

With its help, banking, online exam form submission, admission in any educational institution etc. have been done.

But with this a question of security has also arisen. Many people became victims of various online frauds.

Captcha is also being used keeping internet security in mind. Specific and important information related to this is being described here.

What is captcha?

What is captcha?


Captcha's full name is 'Completely Automated Public Turning Test to Tell Human Apart', which is a challenge.

With its help, it is confirmed on the computer whether the user is a human or not. Such captcha has 'alphabet and number' etc.

which is distorted, as this testing process is done with the help of computer, hence it is also called 'reverse turning test'.

However, this user identification test was also criticized because people with vision impairment have a lot of difficulty in passing this test. A common man takes at least 10 seconds to solve a captcha.

History of captcha -


In the early days of the Internet, many users tried to obscure the text of the pages of various Internet forums, so that the things written in it could be operated only with the help of 'keywords'. 

Over a period of time, it came to be known as 'lit speech'. Leatspeak is a technical term, under which alphabets of different languages ​​are written together. 

The first commercial use of captcha was in 2000 to protect idrive.com sign up page under 'Gausbeck Levchin test'. After this, in the year 2001, PayPal also used it to protect its website users from fraud.

Invention claims of captcha -

It was invented in 2003 by Luis Won Ahn, Manuel Bloom, Nicholas J. Hopper and John Langford. The simplest and most common format of captcha was in 1997. 

At this time it was built by two different groups together. Therefore, both these groups consider themselves to be its first inventors. 

In the first group, the main names are Mark de Lillibridge, Martin population, Krishna Bharat and Andrei J. Border, and in the second group the main names are Iran Reshef, Gilli Ranan and Eileen Solan.

It is a kind of software that performs a web task under replication. It is most used for web spidering. In order to protect the images they had created from the OCR attack, the first team i.e. the first group looked at their 'Brother Scanner' manual, using which the OCR results could be improved. 

The second Luis Vohn's team first defined it in the 2003 edition. After this description, media attention was attracted towards them and this team gained a lot of fame. According to them, all such programs can come under CAPTCHA, which can differentiate between a robot and a human. 

This problem related to the invention claim was solved with the help of the 1997 patent application. The application was named as Iran Reshef, Gilli Runan and Aylon Solan, who had previously worked under the 'Application Security Firewall' of the Scantum. 

His patent application states that 'this invention is designed to solve cognitive and sensory problems of simple computer software.' In 1998, Lillibridge, Abadi, India and Border also made such a patent. 

Although he did not describe the word captcha, he gave a detailed description of his concepts related to it.

Captcha Features -

Modernly, captchas are being made in such a way that three different human competencies can be used at the time of its use. These three capabilities are: invariant recognition, segmentation and parsing. 

Only after crossing these three levels together, further internet related process can be completed. These three qualities are given below.

  • The characters used in captcha are made larger in size under invariant recognition. The human brain can confirm that letter by looking at the innumerable images of a word, but this is not possible for a computer, so this feature is used in the creation of captcha.

  • Under segmentation, one letter is kept separate from the other, but in captcha it is difficult to test. Usually, all the letters in a captcha are seen sticking to each other.

  • Contax or parsing is also created in captcha in such a way that a captcha needs to be viewed in a holistic manner to understand it. For example, if a letter in one of the segments of the captcha looks like 'm', then looking at the entire captcha image as a whole, it can also be an amalgamation of u and n.

These three qualities make a captcha difficult for a web robot and any website and things in it are safe. And the person can solve it easily with his brain.

Captcha Code Uses -

It is used for:

  1. Relation to AI (Artificial Intelligence) : CAPTCHA is used for benchmark task of Artificial Intelligence when used mostly as security. According to Ahn, Blum and Langford, who have established their names among the makers of CAPTCHA, any program that can pass the CAPTCHA test can be used to solve difficult and unresolved AI problems. According to their logic, using it to solve difficult AI problems can give benefits in two ways. Under this, either the problem will remain unresolved and this way of differentiating between computer and human will continue or a difficult problem related to AI will be solved.

  2. Easy to use: Captcha is a 'text reading' task, which can contain letters, numbers, etc. But this task cannot be fulfilled by someone who has some kind of vision defect. However, special audio captcha has also been created for people with vision impairment. Where confirmation can be completed through audio. Captcha has been used in almost every field related to the Internet since its invention. It has been used extensively in People, Gmail, Orkut, Yahoo etc. Here the description of its use area is being given.

  3. For the safety of e-ticketing : Under this, captcha is used for all types of online ticket booking. Whether it is to book a restaurant table, to book a concert ticket, to travel on a plane or train ticket related to the journey, captcha is used in all. The use of captcha in this area protects these companies from major losses. If a hacker executes the ticket booking process with the help of a web robot, then these companies suffer a huge financial loss.

  4. Security of web registration : In the immediate time, many such online facilities have come, where people can enjoy the service for free. If captcha software is not used for them, then it is possible that web robots will create numerous accounts and start having problems in networking. With this, there can be problem of email spam etc. and personal information of many people may be in danger. Because of this it is also used for online sites.

  5. To protect online poll : Web robots are most commonly used to influence online voting. A hacker can use it to win a candidate. Therefore, captcha is used in online polling to protect online poll from this effect.

  6. To protect the blog from spam : Anyone can access the comment section of a blog. Therefore, if this area is not kept safe, then various types of promotions etc. also start coming. Because of this, the truth and reputation of the blog starts to be affected. It is also used to protect the blog from this ill-effect.

Captcha tricks-

There have been many tricks to influence captcha, which are used by various hackers for misdeeds to break it illegally. Various types of attacks on captcha are described below.

  • A paper under I.E.E. was edited by mori et al, which described captcha breaking. Under this paper, it was found out that a captcha is likely to be broken up to 92%. Under this paper, it was found that only 33% of the Gippy program is broken.

  • PWNtcha has played a better role in defeating Captcha. Because of this, now the best type of captcha can be created.

  • A security company called Kasperskai created a Trojan named Podak. This extends the Trojan captcha to an 'online human service'. Here any captcha image is converted into text and in this way it becomes easy to cheat the captcha.

Optional Captcha Scheme-

It is very easy to break text distortion type captcha with machine learning based attacks. In many research, an alternative captcha was proposed, so that it can be made more secure. Some alternative captcha are described below.

  • Chew et al decided to create a separate image recognition captcha at the time of the seventh International Information Security. At the same time, it was revealed in a proposal that an anomaly captcha is 100 percent better for human use.

  • Datta et al spoke about the captcha titled 'Imagination' through his paper under the conference of ACM Multimedia. The full form of the word Imagination is "Image Generation of Internet Authentication". Such captchas use images and these images are distorted in such a way that the state of the art image recognition also fails in its investigation.

  • Microsoft has also created captcha on behalf of its company. His captcha is titled 'Animal Spices Recognition for Restricting Assays'. Images of this captcha are often told to distinguish between a dog and a cat. According to Microsoft, a user can use Asirra (Animal Spices Recognition for Restricting Assays) very easily. This can be solved by about 99.6% of humans, requiring only 30 seconds. This type of captcha is also being used a lot in the internet world.

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