In this paper, we have proposed a system to grade CAPTCHA strength, according to various parameters determined by breaking the CAPTCHA. There are basically four major steps involved in the system.First step is preprocessing which includes – binarization and noise removal.Second step is segmenting the image into individual characters. Third step is to obtain skeletons of characters i.e., Thinnin...

This study focuses on a machine learning approach to the CAPTCHA recognition problem that requires minimal preprocessing of inputs. Both the feed-forward neural nets and the self-organizing maps used in this study took the raw image pixels as input with only simple segmentation and translation performed in advance. The models were trained and tested on four and five letter CAPTCHAs using either...

CAPTCHAs is an interesting of research are short for Completely Automated Public Turing test to tell Computers and Humans Apart. The purpose of a CAPTCHA is to block form submissions from spam bots –automated scripts that harvest email addresses from publicly available web forms. We introduce a new CAPTCHA which is based on identifying the color of image, object or background. This actually req...

We present a new method for image taxonomy. Our formulation shows how the combination of automated metadata-based analysis and knowledge-acquisition tools can help build better image search applications. We build on top of existing metadata-based techniques to image taxonomy and combine them to human assistance, in order to guarantee some minimal level of semantic soundness. Knowledge from huma...

As a result of continuing advances in computer capabilities, it is becoming increasingly difficult to distinguish between humans and computers in the digital world. We propose using the fundamental human ability to distinguish between things that are aesthetically pleasing and those that are not as the basis of a method to verify that a communicating party is human. We discuss one possible impl...

Spam over internet telephony (SPIT) refers to all unsolicited and massive scale attempts to establish voice communication with oblivious users of voice over internet protocol (VoIP) services. SPIT exhibits a significant increase over the last years, thus developing into a serious threat with adverse impact and costs for the business economy. An audio completely automated public Turing test to t...

This paper studies reverse Turing tests to tell humans and computers apart. Contrary to classical Turing tests, the judge is not a human but a computer. These tests are often called Completely Automated Public Turing tests to tell Computers and Humans Apart (CAPTCHA). The main purpose of such test is avoiding automated usage of various services, preventing bots from spamming on forums, securing...

Audio CAPTCHA systems, which distinguish between software agents and human beings, are especially important for persons with visual disability. The popular approach is based on mixing-based methods (MBM), which use the mixed sounds of target speech and noises. We have proposed a deletion-based method (DBM) which uses the phonemic restoration effects. Our approach can control the difficulty of t...

In an on-line transaction, a client usually have to present some authenticators (password, user certificate or both) to the server. However, those authenticators are exposed to client-side malware such that the malware is able to obtain the server-client messages, or impersonate the user to build another “secure” channel with the server. The present paper aims to patch this client-side security...