A SEMINAR ON CAPTCHA By- ABHIMANYU SOOD 0902810002 (C.S.E.) DEPARTMENT OF COMPUTER SCEINCE AND ENGINEERING IDEAL INSTITUTE OF TECHNOLOGY, GHAZIABAD [U.P.] (Approved by AICTE and affiliated to GBTU, Lucknow U.P.) 2011-2012
CAPTCHA: Outline Meaning of CAPTCHA Origin of CAPTCHA Different types of CAPTCHA Application of CAPTCHA Properties of CAPTCHA Circumvention/Breaking of CAPTCHA Reference Conclusion
CAPTCHA: Acronym Completely Automated Public Turing Test to Tell Computers and Humans Apart
CAPTCHA: Meaning Completely - Whole Automated - Made by machine Public - Universally known Turing Test to Tell - Test presented by Alan Turing Computers and Humans Apart
CAPTCHA: Origin 1997: Andrei Broder at AltaVista wanted to prevent bots from automatically submitting sites for indexing He decided to add a test to the submission page He performed a reverse scan through Optical Character Recognition(OCR) scanner 2000: Luis von Ahn, Manuel Blum & John Langford at CMU coined term CAPTCHA
CAPTCHA: Deciding Human or Bot? A puzzle or problem that is easy for humans to solve and very difficult for computers is given If the puzzle is solved correctly, you are considered human and can continue Also known as reverse Turing Test- Human Interaction Proof.
PRINTED CAPTCHA Printed CAPTCHA is difficult to break Lots of algorithms are available to generate these Computers cannot identify these easily Two major types are there viz. Baffle text, Pessimal print.
PRINTED CAPTCHA: Baffle Developed by Monica Chew and Henry Baird Uses pronounceable English characters(with various masking techniques)that are not present in English dictionary
PRINTED CAPTCHA: Pessimal Developed by Allison Coates and Henry Baird and Richard Fateman Uses the degradation model simulating physical defects caused by printing and scanning of printed text
HANDWRITTEN CAPTCHA Less frequently used because computers can easily identify the handwriting rather than text images (OCR Scanners) Use of transformations by adding lines, arcs, circles etc.
CAPTCHA: Advanced Types Text based Ez-gimpy R-gimpy (Google) Simard’s HIP (MSN) Graphic based Bongo Pix
CAPTCHA: Advanced Types Audio based Face Recognition Logic Puzzles KittenAuth
CAPTCHA: Text Based Gimpy, ez-gimpy Pick a word or words from a dictionary Distort them and, add noise and background Gimpy-r, Google’s CAPTCHA Pick random letters Distort them and, add noise and background
CAPTCHA: Text Based Simard’s HIP Pick random letters and numbers Distort them and add arcs
CAPTCHA: Graphics Based (Bongo) A visual recognition problem Two sets of shapes with a distinguishing characteristic Must choose which set the shape belongs to
CAPTCHA: Graphics Based (Pix) A database of labeled images of recognizable objects Randomly chooses an object and displays N pictures of it Must correctly identify the object Pictures can or cannot be distorted
CAPTCHA: Audio Pick a word or a sequence of numbers at random Render them into an audio clip using a Text To Speech (TTS) software Distort the audio clip Ask the user to identify and type the word or numbers
CAPTCHA: Logic Puzzles Easy trivia questions Example: Which of the following is a bird? Elephant, Tiger, Robin Simple mathematical expressions: What is the solution? (2+2) It’s very accommodating to create a big enough database of these simple logic based puzzles
CAPTCHA: KittenAuth “The Cutest Human Test” A 3x3 matrix of cute animals Choose the 3 kittens Strategy is to use animals that look similar to kittens
CAPTCHA: Properties CAPTCHA should be automatically generated and graded for good performance Test can be taken quickly and easily by human users Test will accept virtually all human users and reject software agents Test has been able to resist attacks for many years, despite the technological advances and knowledge of algorithms, but are they full-proof ??
CAPTCHA: Circumvention (Breaking) Introducing bugs in the system, so that it allows the attacker to completely bypass the CAPTCHA. Improving character recognition software. Using cheap Human labour to process the tests(impractical in real world), & as done by Humans so the purpose of CAPTCHA still holds.
CAPTCHA: Circumvention (Breaking) Pre-Processing: Removal of background clutter and noise. Classification: Identifying the character in each region. Segmentation: Splitting the image into regions which each contain a single character.
CAPTCHA: Conclusion They are crucial to preventing bot attacks Hopefully, they will become more user-friendly to people with disabilities (visual/mental) CAPTCHA’s are mainly produced from Asynchronous Java-script And XML (AJAX) & using a bit of Hypertext Preprocessor (PHP) technology Various algorithms are present
CAPTCHA: Reference WIKIPEDIA GOOGLE http://captchas.net Numerous sites that provide various students like us to gather, discuss & help each other– http://www.scribd.com/ http://www.slideshare.net/