logging in or signing up semianr on captcha sowjanya_kandisa Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT lite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: Embed: Flash iPad Copy Does not support media & animations WordPress Embed Customize Embed URL: Copy Thumbnail: Copy The presentation is successfully added In Your Favorites. Views: 7454 Category: Science & Tech.. License: All Rights Reserved Like it (27) Dislike it (1) Added: March 07, 2010 This Presentation is Public Favorites: 5 Presentation Description No description available. Comments Posting comment... By: manash11 (7 month(s) ago) pla give me the link to download erp ppt... Saving..... Post Reply Close Saving..... Edit Comment Close By: manash11 (7 month(s) ago) pla give me the link to download erp ppt... Saving..... Post Reply Close Saving..... Edit Comment Close By: srtkundu (13 month(s) ago) plz send captcha ppts to me.. sarikundu@gmail.com Saving..... Post Reply Close Saving..... Edit Comment Close By: srtkundu (13 month(s) ago) plz send captcha ppts to me.. sarikundu@gmail.com Saving..... Post Reply Close Saving..... Edit Comment Close By: srtkundu (13 month(s) ago) plz send captcha ppts to me.. sarikundu@gmail.com Saving..... Post Reply Close Saving..... Edit Comment Close loading.... See all Premium member Presentation Transcript Slide 1: captcha A presentation on captcha Presented By:- Astha Agrawal MCA 4th Sem CONTENTS : CONTENTS Introduction Process History Guidelines Applications How to defeat captchas More accessible captchas Image recognition captchas Summary FULL FORM : FULL FORM It is a contrived acronym for "Completely Automated Public Turing test to tell Computers and Humans Apart." INTRODUCTION : INTRODUCTION A PROGRAM THAT CAN TELL WHETHER ITS USER IS A HUMAN OR A COMPUTER A CAPTCHA or Captcha is a type of challenge-response test used in computing to ensure that the response is not generated by a computer Slide 5: EXAMPLE Slide 6: A PROGRAM THAT CAN GENERATE AND GRADE TESTS THAT: A. MOST HUMANS CAN PASS B. CURRENT COMPUTER PROGRAMS CANNOT PASS REVERSE TURING TEST : REVERSE TURING TEST It is sometimes described as a Reverse Turing Test because it is administered by a machine and targeted to a human, in contrast to the standard Turing test that is typically administered by a human and targeted to a machine. A common type of CAPTCHA requires that the user type letters or digits from a distorted image that appears on the screen. PROCESS : PROCESS The process usually involves one computer (a server) asking a user to complete a simple test which the computer is able to generate and grade. Because other computers are unable to solve the CAPTCHA, any user entering a correct solution is presumed to be human. Slide 9: Picks a random string of letters : o m a g Renders it to a distorted image:- Slide 10: ... and generates a test TYPE THE CHARACTERS THAT APPEAR IN THE IMAGE HISTORY : HISTORY Moni Naor was the first person to theorize a list of ways to verify that a request comes from a human and not a bot.[4] Primitive CAPTCHAs seem to have been developed in 1997 by Andrei Broder, Martin Abadi, Krishna Bharat, and Mark Lillibridge to prevent bots from adding URLs to their search engine. Slide 12: Early CAPTCHAs such as these, generated by the EZ-Gimpy program, were used on Yahoo Slide 13: However, technology was developed to read this type of CAPTCHA A modern CAPTCHA, rather than attempting to create a distorted background and high levels of warping on the text, might focus on making segmentation difficult by adding an angled line Slide 14: Another way to make segmentation difficult is to crowd symbols together. This is Yahoo!'s current CAPTCHA format. This might be difficult for some people to read, as seen in the leftmost example Is it "klopsh" or "kbpsh"?. Guidelines : Guidelines Accessibility Image Security Script Security Security Even After Wide-Spread Adoption. Applications : Applications Preventing Comment Spam in Blogs. Protecting Website Registration. Online Polls Preventing Dictionary Attacks. Search Engine Bots Worms and Spam. HOW TO DEFEAT CAPTCHAS : HOW TO DEFEAT CAPTCHAS There are a few approaches to defeating CAPTCHAs: 1. exploiting bugs in the implementation that allow the attacker to completely bypass the CAPTCHA, 2. improving character recognition software. 1. pre-processing 2. segmentation 3. classification 3. using cheap human labor to process the tests ATTEMPTS AT MORE ACCESSIBLE CAPTCHAs : ATTEMPTS AT MORE ACCESSIBLE CAPTCHAs Even an audio and visual CAPTCHA will require manual intervention for some users, such as those who have visual disabilities and also are deaf. There have been various attempts at creating CAPTCHAs that are more accessible. Attempts include the use of JavaScript, mathematical questions ("what is 1+1"), or "common sense" questions ("what color is the sky on a clear day"). IMAGE RECOGNITION CAPTCHAs : IMAGE RECOGNITION CAPTCHAs phpBB forum software have implemented in an open source image recognition captcha system which in its default form presents a question requiring the user to select a stated type of animal from an array of thumbnail images of assorted animals. Slide 20: PIX WHAT ARE THESE PICTURES OF ? SUMMARY : SUMMARY Completely Automated Public Turing test to tell Computers and Humans Apart is a captcha Slide 22: Thank you You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.
semianr on captcha sowjanya_kandisa Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT lite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: Embed: Flash iPad Copy Does not support media & animations WordPress Embed Customize Embed URL: Copy Thumbnail: Copy The presentation is successfully added In Your Favorites. Views: 7454 Category: Science & Tech.. License: All Rights Reserved Like it (27) Dislike it (1) Added: March 07, 2010 This Presentation is Public Favorites: 5 Presentation Description No description available. Comments Posting comment... By: manash11 (7 month(s) ago) pla give me the link to download erp ppt... Saving..... Post Reply Close Saving..... Edit Comment Close By: manash11 (7 month(s) ago) pla give me the link to download erp ppt... Saving..... Post Reply Close Saving..... Edit Comment Close By: srtkundu (13 month(s) ago) plz send captcha ppts to me.. sarikundu@gmail.com Saving..... Post Reply Close Saving..... Edit Comment Close By: srtkundu (13 month(s) ago) plz send captcha ppts to me.. sarikundu@gmail.com Saving..... Post Reply Close Saving..... Edit Comment Close By: srtkundu (13 month(s) ago) plz send captcha ppts to me.. sarikundu@gmail.com Saving..... Post Reply Close Saving..... Edit Comment Close loading.... See all Premium member Presentation Transcript Slide 1: captcha A presentation on captcha Presented By:- Astha Agrawal MCA 4th Sem CONTENTS : CONTENTS Introduction Process History Guidelines Applications How to defeat captchas More accessible captchas Image recognition captchas Summary FULL FORM : FULL FORM It is a contrived acronym for "Completely Automated Public Turing test to tell Computers and Humans Apart." INTRODUCTION : INTRODUCTION A PROGRAM THAT CAN TELL WHETHER ITS USER IS A HUMAN OR A COMPUTER A CAPTCHA or Captcha is a type of challenge-response test used in computing to ensure that the response is not generated by a computer Slide 5: EXAMPLE Slide 6: A PROGRAM THAT CAN GENERATE AND GRADE TESTS THAT: A. MOST HUMANS CAN PASS B. CURRENT COMPUTER PROGRAMS CANNOT PASS REVERSE TURING TEST : REVERSE TURING TEST It is sometimes described as a Reverse Turing Test because it is administered by a machine and targeted to a human, in contrast to the standard Turing test that is typically administered by a human and targeted to a machine. A common type of CAPTCHA requires that the user type letters or digits from a distorted image that appears on the screen. PROCESS : PROCESS The process usually involves one computer (a server) asking a user to complete a simple test which the computer is able to generate and grade. Because other computers are unable to solve the CAPTCHA, any user entering a correct solution is presumed to be human. Slide 9: Picks a random string of letters : o m a g Renders it to a distorted image:- Slide 10: ... and generates a test TYPE THE CHARACTERS THAT APPEAR IN THE IMAGE HISTORY : HISTORY Moni Naor was the first person to theorize a list of ways to verify that a request comes from a human and not a bot.[4] Primitive CAPTCHAs seem to have been developed in 1997 by Andrei Broder, Martin Abadi, Krishna Bharat, and Mark Lillibridge to prevent bots from adding URLs to their search engine. Slide 12: Early CAPTCHAs such as these, generated by the EZ-Gimpy program, were used on Yahoo Slide 13: However, technology was developed to read this type of CAPTCHA A modern CAPTCHA, rather than attempting to create a distorted background and high levels of warping on the text, might focus on making segmentation difficult by adding an angled line Slide 14: Another way to make segmentation difficult is to crowd symbols together. This is Yahoo!'s current CAPTCHA format. This might be difficult for some people to read, as seen in the leftmost example Is it "klopsh" or "kbpsh"?. Guidelines : Guidelines Accessibility Image Security Script Security Security Even After Wide-Spread Adoption. Applications : Applications Preventing Comment Spam in Blogs. Protecting Website Registration. Online Polls Preventing Dictionary Attacks. Search Engine Bots Worms and Spam. HOW TO DEFEAT CAPTCHAS : HOW TO DEFEAT CAPTCHAS There are a few approaches to defeating CAPTCHAs: 1. exploiting bugs in the implementation that allow the attacker to completely bypass the CAPTCHA, 2. improving character recognition software. 1. pre-processing 2. segmentation 3. classification 3. using cheap human labor to process the tests ATTEMPTS AT MORE ACCESSIBLE CAPTCHAs : ATTEMPTS AT MORE ACCESSIBLE CAPTCHAs Even an audio and visual CAPTCHA will require manual intervention for some users, such as those who have visual disabilities and also are deaf. There have been various attempts at creating CAPTCHAs that are more accessible. Attempts include the use of JavaScript, mathematical questions ("what is 1+1"), or "common sense" questions ("what color is the sky on a clear day"). IMAGE RECOGNITION CAPTCHAs : IMAGE RECOGNITION CAPTCHAs phpBB forum software have implemented in an open source image recognition captcha system which in its default form presents a question requiring the user to select a stated type of animal from an array of thumbnail images of assorted animals. Slide 20: PIX WHAT ARE THESE PICTURES OF ? SUMMARY : SUMMARY Completely Automated Public Turing test to tell Computers and Humans Apart is a captcha Slide 22: Thank you