The CAPTCHA (Completely Automated Turing test to tell Computers and Humans Apart) is found throughout many websites. By challenging users read a line of scrambled letters, identify crosswalks in an image, or some complete another task that difficult for computer do, but comparatively trivial human user, verifies the user actual human, not software meant interact maliciously with website. This m...

Online services which allow users to contribute content and interact remotely over the internet in some manner are common today. Many of these services, like spam control for blogs and email account sign-up, require that they be accessed only by humans and not machines (automated scripts or bots). One method of differentiating between humans and bots is by using a CAPTCHA (Completely Automated ...

We propose in this paper a public key watermarking algorithm for image integrity veri cation. This watermark is capable of detecting any change made to an image, including changes in pixel values and image size. This watermark is important for several imaging applications, including trusted camera, legal usage of images, medical archiving of images, news reporting, commercial image transaction,...

Digital Watermarking is seen as a viable solution to authentication of multimedia data and hence its security, especially in a networked environment. In this paper we present a new watermarking technique to add a code to digital images in spatial domain. This technique is further shown to be robust under common compression schemes, including lossy compression schemes. Watermark embedding is don...

The internet and web security are integral aspects of our daily lives. Many commercial firms provide clients with services. For access, it is assumed that only the genuine user, who a human, will register. Yet automated hacking programs can also do registrations fake data consume lot bandwidth, slowing down or occasionally even shutting websites, leading to Distributed denial-of-service (DDOS) ...

A Completely Automated Public Turing Test to Tell Computers and Humans Apart (CAPTCHA) is a simple test that used on websites differentiate between human users automated attacks indulge in spamming other fraudulent activities. text-based CAPTCHA the most popular security technique by many Internet, such as Microsoft, Google eBay, secure their sites from attacks. By design, however, unable legit...