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Published on March 20, 2014

Author: goldi30


PowerPoint Presentation: TOPIC: CAPTCHA - A HUMAN INTERACTION PROOF SRUSHTI R. AREKAR PUNE BY: CONTENTS:: CONTENTS: Introduction Reason To Give Test? Captcha Logic. What Is Turing Test? Reverse Turing Test. Types Of Captcha Working Of Captcha Re-captcha Working Of Re-captcha Characteristics Issues With Captcha Applications Conclusions References 2 PowerPoint Presentation: 3 INTRODUCTION:: INTRODUCTION: The term "CAPTCHA" was coined in 2000 by Luis Von Ahn, Manuel Blum , Nicholas J. Hopper and John Langford of Carnegie Mellon University. 4 CAPTCHA stands for “Completely Automated Public Turing Test to Tell Computers and Humans Apart.” PowerPoint Presentation: 5 You're trying to sign up for a free email service offered by Gmail or Yahoo. Before you can submit your application, you first have to pass a test. It's not a hard test - in fact, that's the point . For you, the test should be simple and straightforward. But for a computer, the test should be almost impossible to solve. This sort of test is a   CAPTCHA . They're also known as a type of   Human Interaction Proof (HIP ). The most common form of CAPTCHA is an image of several distorted letters. It's your job to type the correct series of letters into a form. If your letters match the ones in the distorted image, you pass the test. Why to give the TEST ???: Why to give the TEST ??? Ticketmaster (Ticket Broker): It is possible for a scalper to use a bot to place hundreds or thousands of ticket orders in a matter of seconds. Regular customers become victims, as tickets can be selled only if they are available. Scalpers then try to sell the tickets above face value. CAPTCHA test in this case prevents scalping and proves that you are human. Yahoo, Hotmail, or Gmail (free e-mail service): A free e-mail service might find itself bombarded by account requests from an automated program. That automated program could be part of a larger attempt to send out spam mail to millions of people. CAPTCHA test in this case prevents creation of spam mails and accounts. 6 CAPTCHA LOGIC :: CAPTCHA LOGIC : 7 The user is presented with a garbled image on which some text is displayed. This image is generated by the server using random text. The user must enter the same letters in the text into a text field that is displayed on the Form. When the Form is submitted, the server checks if the text entered by the user matches the initial generated text. If it does, the transaction continues. Otherwise, an error message is displayed and the user has to enter a new code.   TURING TEST:  TURING TEST Proposed by Alan Turing (father of Modern Computation). To test a machine’s level of intelligence. In standard Turing test, questions are targeted to a machine and human and if the answers of both are same ,then machine passes the Turing test. 8 Alan Turing REVERSE TURING TEST:: REVERSE TURING TEST: CAPTCHA employs a Reverse Turing Test. JUDGE = CAPTCHA PROGRAM , PARTICIPANT = USER If the user passes CAPTCHA , it is human otherwise it is a spam program. 9 TYPES OF CAPTCHAS:  TYPES OF CAPTCHAS There are two main type of captcha: 1.Text -Gimpy - Ez – Gimpy -Baffle Text -MSN Captcha 2.Graphics -Bongo -PIX 3.Audio (special case) (it is mainly used for visual impaired people) 10 1. TEXT CAPTCHA ::  1. TEXT CAPTCHA : These are simple to implement. Examples of such questions are: (i) What are 20 -3= ____ ? (ii) What is the third letter in word “UNIVERSITY” ? (iii) Which of Yellow, Thursday and Richard is a color ? (iv) If yesterday was a Sunday, what is today ? These are also friendly to people with visual disability – such as those with colour blindness. 11 1.1 GIMPY :: 1.1 GIMPY : Gimpy is a very reliable text CAPTCHA built by CMU (Carnegie Mellon University) in collaboration with Yahoo for their Messenger service. Gimpy works by choosing ten words randomly from a dictionary, and displaying them in a distorted and overlapped manner. Gimpy then asks the users to enter a subset of the words in the image. The human user is capable of identifying the words correctly, whereas a computer program cannot. 12 1.2 EZ- GIMPY:: 1.2 EZ- GIMPY: This is a simplified version of the Gimpy CAPTCHA, adopted by Yahoo in their signup page. Ez – Gimpy randomly picks a single word from a dictionary and applies distortion to the text. The user is then asked to identify the text correctly. 13 body blocked 1.3 BAFFLED TEXT:: 1.3 BAFFLED TEXT: This was developed by Henry Baird at University of California at Berkeley. This doesn’t contain dictionary words, but it picks up random alphabets to create a nonsense but pronounceable text. Distortions are then added to this text and the user is challenged to guess the right word. This technique overcomes the drawback of Gimpy CAPTCHA because, Gimpy uses dictionary words and hence, clever bots could be designed to check the dictionary for the matching word by brute-force. 14 ourses finans 1.4 MSN CAPTCHA:: 1.4 MSN CAPTCHA: It is designed by MICROSOFT for Microsoft utilities. These are popularly called MSN Passport CAPTCHAs. They use eight characters (upper case) and digits. Foreground is dark blue, and background is grey. Warping is used to distort the characters, to produce a ripple effect, which makes computer recognition very difficult. 15 XTNM5YRE L9D28229B 2. GRAPHIC CAPTCHAs:: 2. GRAPHIC CAPTCHAs: 2.1 BONGO : Bongo. Another example of a CAPTCHA is the program we call BONGO. BONGO is named after M.M. Bongard, who published a book of pattern recognition problems in the 1970s. BONGO asks the user to solve a visual pattern recognition problem. It displays two series of blocks, the left and the right. The blocks in the left series differ from those in the right, and the user must find the characteristic that sets them apart. A possible left and right series is shown in Figure. 16 2.2 PIX:: 2.2 PIX: In PIX, we have some distorted ,concrete images. (like a horse, a table, a house, a flower). The program picks an object at random, finds six images of that object from its database, presents them to the user and then asks the question “what are these pictures of?” PIX as stated is not a CAPTCHA , to make it a CAPTCHA we have to distort it so that program cannot easily recognize it. 17 PIX IMAGE PIX CAPTCHA 3. Audio CAPTCHAs:: 3. Audio CAPTCHAs: The program picks a sequence of characters or numbers at random, renders the word or the numbers into a sound clip and distorts the sound clip; it then presents the distorted sound clip to the user and asks users to enter its contents. This CAPTCHA is based on the difference in ability between humans and computers in recognizing spoken language. 18 How CAPTCHA works?: How CAPTCHA works? 19 Create a random string. Store it. Generate an Image. Match it with the stored one in the Database. If match found then form is accepted else form rejected. PowerPoint Presentation:  Roughly about 200 million CAPTCHAs are typed everyday !! About 10 secs of human time is utilized per CAPTCHA. So essentially whole humanity is wasting about 5,00,000 hrs in typing these annoying CAPTCHAs. 20 Can we use this human effort for good?: Can we use this human effort for good? In this 10 secs, human brain is doing something amazing which computers can’t do yet!! And there comes the evolution of the term RE-CAPTCHA !! 21 RE-CAPTCHA : Re-inventing CAPTCHA: RE-CAPTCHA : Re-inventing CAPTCHA Some CAPTCHA creators came up with a way to increase the value of such an application: digitizing books . An application called reCAPTCHA makes user responses in CAPTCHA fields to verify the contents of a scanned piece of paper. Because computers aren't always able to identify words from a digital scan, humans have to verify what a printed page says. 22 How RE-CAPTCHA works:: How RE-CAPTCHA works: First, the administrator digitally scans a book . Then, the reCAPTCHA program selects two words from the digitized image . The application already recognizes one of the words . User types 1’st word . The application program verifies it . If correct, then it assumes the second word the user types is also correct . That second word goes into a pool of words that the application will present to other users. As each user types in a word, the application compares the word to the original answer. Eventually, the application receives enough responses to verify the word with a high degree of certainty. That word can then go into the verified pool . 23 PowerPoint Presentation: 24 PowerPoint Presentation: 25 PowerPoint Presentation: 26 CHARACTERISTICS:: CHARACTERISTICS: A CAPTCHA is a means of automatically generating challenges for computer. Provides a problem easy enough for all humans to solve. Prevent automated software from filling out a online forms . CAPTCHAs do not have to rely on difficult problems in artificial intelligence, although they can. This has the benefit of distinguishing humans from computers . It also creates incentive to further develop artificial intelligence of computers 27 Issues with CAPTCHAs: Issues with CAPTCHAs Distortion becomes a problem when it is done in a very haphazard way. Some characters like ‘d’ can be confused for ‘cl’ or ‘m’ with ‘rn’. It should also be easily understandable to those who are unfamiliar with the language. Content is an issue when the string length becomes too long or when the string is not a dictionary word. Care should be taken not to include offensive words. Presentation should be in such a way as to not confuse the users. The font and colour chosen should be user friendly. 28 Applications::  Applications: Online Polls : Programs are designed to continuously vote for the team. CAPTCHAs prevent from sabotaging. Protecting Website Registration : Preventing from creating of spam email accounts on free email services E-Ticketing : Prevention of purchasing of online tickets by a program. Email spam : Prevention of creation of spam emails As a tool to verify digitized books : help in digitizing books. 29 CONCLUSION:: CONCLUSION: It is important to learn about these techniques, due to increasing security threats and web attacks. Captcha prevents unauthorized user from getting enter into the sites before time. It also provides us the guarantee that the person at the other end is a human being instead of any computer program that may hack the system. Being able to learn about different CAPTCHAs, we can defend ourselves in an effective manner . We learnt about how to defend ourselves from such attacks at both the user as well as at the organization level . 30 REFERENCES :: REFERENCES : Sarika Choudhary “Understanding Captcha: Text and Audio Based Captcha with its Applications“, International Journal of Advanced Research in Computer Science and Software Engineering Research Paper , Volume 3, Issue 6, June 2013. Ahn, L. von, Blum, M., & Langford, J., (2003) “Telling humans and computers apart automatically”, Communications of the ACM, vol 46, August, pp 57-60. Rich Gossweiler, Maryam Kamvar, Shumeet Baluja: “What’s Up CAPTCHA?” A CAPTCHA Based on Image Orientation C. M. University The Official CAPTCHA Site. 31 PowerPoint Presentation: 32 CAPTCHA INVENTORS: LUIS VON AHN MANUEL BLUM NICHOLAS J. HOPPER JOHN LANGFORD MY SPECIAL THANKS TO: COMPUTER DEPARTMENT BHARATI VIDYAPEETH COLLEGE OF ENGINEERING, PUNE -43. THANK YOU

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