reCaptcha is a very popular CAPTCHA system on the Internet. Due to its design, we find that reCaptcha figures have certain feature that can potentially weaken this system. This paper discussed the design of reCaptcha, and use some simple Machine Learning algorithm to find a way to tell the difference between “control word” and “unknown word”. We also designed the experiment to evaluate our hypo...

the semantic network of the preposition 'ba' in persian: a cognitive study as one of the widely used prepositions in persian, 'ba' (i.e. with) may also function as an adjective particle or affix. this paper studies various meanings of preposition 'ba' within a cognitive lexical semantics framework. it aims to show that the various meanings of this preposition do not emerge randomly. drawing the...

artificial immune systems (ais) can be defined as soft computing systems inspired by immune system of vertebrates. immune system is an adaptive pattern recognition system. ais have been used in pattern recognition, machine learning, optimization and clustering. feature reduction refers to the problem of selecting those input features that are most predictive of a given outcome; a problem encoun...

CAPTCHAs have been deployed ubiquitously by web sites to combat automated malicious programs. Security against web bots and usability to legitimate users are two main goals that have to be simultaneously satisfied when designing a useful CAPTCHA scheme. However, there exists a well-known and intricate trade-off between these goals. So far, balancing this trade-off remains an art rather than a s...

in this paper, the performance of 11 different distances for image retrieval and classification, based on color, shape and texture, is evaluated. the precision-recall measure and the correct classification rate of the k-nn classifier are used to evaluate retrieval and classification performances, respectively. the experimental results for a database of 1000 images from 10 different semantic gro...

Segmentation subdivides a CAPTCHA image into its constituent regions or objects. The point to which the subdivision is carried depends on the problem being solved. That is, segmentation should end when the objects of interest inan application have been isolated. Without a good segmentation algorithm, an object may never be identifiable. Image segmentation continues to be an vital and active res...

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...