YAPPTCHA: Yet another picture promoted CAPTCHA with spam stopping, image labeling and SIFT accomplishment

We present YAPPTCHA, a new CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) as a security measure to recognize human users. The proposed system uses images instead of distorted text to label images as a valuable output. YAPPTCHA is generated from images on the Web. In order to solve this type of CAPTCHA, users must type two words for description of two images. When users pass the challenge, the provided meaningful labels are used to determine the content of images. In addition, semantic graphs for labels and images are created and it will make it possible to develop an image semantic search engine accordingly. Due to usage of images in this system, and its architecture, it is highly secure compared to its counterparts. In a user study involving 60 participants, YAPPTCHA´s word accuracy is measured to be 98.18% while 61.26% of attempts of the users were successful.