One common trend in image tagging research is to focus on visually relevant tags, and this tends to ignore the personal and social aspect of tags, especially on photoblogging websites such as Flickr. Previous work has correctly identified that many of the tags that users provide on images are not visually relevant (i.e. representative of the salient content in the image) and they go on to treat...

Tags have been popularly utilized for better annotating, organizing and searching for desirable images. Image tagging is the problem of automatically assigning tags to images. One major challenge for image tagging is that the existing/training labels associated with image examples might be incomplete and noisy. Valuable prior work has focused on improving the accuracy of the assigned tags, but ...

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...

Associating labels with online products can be a laborintensive task. We study the extent to which a standard “bag of visual words” image classifier can be used to tag products with useful information, such as whether a sneaker has laces or velcro straps. Using Scale Invariant Feature Transform (SIFT) image descriptors at random keypoints, a hierarchical visual vocabulary, and a variant of near...

We propose an approach that unifies browsing by tags and visual features for intuitive exploration of image databases. In contrast to traditional image retrieval approaches, we utilise tags provided by users on collaborative tagging sites, complemented by simple image analysis and classification. This allows us to find new relations between data elements. We introduce the concept of a navigatio...

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...