Animated Ink-Blot Images Keep Unwanted Bots at Bay New Scientist (11/03/09) Barras, Colin
as it appeared in the November 4, 2009 edition of ACM TechNews.
Indian Institute of Technology Dehli computer scientist Niloy Mitra says that Completely Automated Public Turing test to tell Computers and Humans Apart (CAPTCHA) security tests would be more difficult for computers to solve, and easier for humans, if they were animated. Mitra, along with Tel Aviv University's Daniel Cohen-Or and colleagues in Taiwan, have developed "emerging images," which are seemingly random assortments of blotches from which a coherent image emerges after a few seconds. To create the emerging image, the researchers developed an algorithm that identifies key features within an original image and converts those features into an array of ink blots. The algorithm then removes a number of the splats to make it harder for bots to reconstruct the original shape while leaving enough information for a human to identify the image. The number of splats and the background noise can be adjusted to make the emerging image easier or harder to spot. Tests on 310 volunteers showed that 98 percent recognized more than 80 percent of the emerging images at the easy setting. And a test of three state-of-the-art software systems found that computers were only able to identify whether an image contained a horse or a human 51 percent to 60 percent of the time. When the researchers used the algorithm to convert three-dimensional animations into emerging videos, they found that all volunteers could spot the animated figure even when the emergence setting was on very hard. Mitra says adding animation makes recognition much easier for humans and much more difficult for computers. View Full Article
