A 3-layer Dynamic CAPTCHA Implementation

Abstract

In order to avoid tremendous attack from malicious computer programs, CAPTCHA (Completely Automated Public Turing test to tell Computers and Human Apart) mechanism has been introduced to distinguish humans and computers. Due to the fast development of pattern recognition and artificial intelligence technology, there are increasing safety loopholes concerning traditional 2D static CAPTCHAs, resulting in that certain malicious computer programs could launch serious program attack through breaking such CAPTCHAs. In this article, we proposal a practical and safe 3-layer dynamic CAPTCHA, originally bonding the biological vision theory with the single-frame zero-knowledge theory, ensuring it not only extremely hard to recognize each single frame, but easy to identify for humans as well. It also makes full use of disadvantages of computers in recognizing numerous moving objects from a complicated background, making it still very difficult for computer programs to break even using several frames. To verify its security, an analysis is further carried out. Moreover, the 3-layer structure makes the design of CAPTCHA more distinct, taking on high expansibility as well as plenty of room for sustainable optimization.