CAPTCHAs are employed as a security measure to differentiate human users from bots. A new sound-based CAPTCHA is proposed in this paper, which exploits the gaps between human voice and synthetic voice rather than relays on the auditory perception of human. The user is required to read out a given sentence, which is selected randomly from a specified book. The generated audio file will be analyzed automatically to judge whether the user is a human or not. In this paper, the design of the new CAPTCHA, the analysis of the audio files, and the choice of the audio frame window function are described in detail. And also, some experiments are conducted to fix the critical threshold and the coefficients of three indicators to ensure the security. The proposed audio CAPTCHA is proved accessible to users. The user study has shown that the human success rate reaches approximately 97% and the pass rate of attack software using Microsoft SDK 5.1 is only 4%. The experiments also indicated that it could be solved by most human users in less than 14 seconds and the average time is only 7.8 seconds.
D-CAPTCHA++: A Study of Resilience of Deepfake CAPTCHA under Transferable Imperceptible Adversarial Attack
School of Computer Science（计算机学院）；University College Dublin（都柏林大学学院）；School of Computer Science and Statistics（计算机与统计学院）；Trinity College Dublin（都柏林圣三一学院）；University of Science（科学大学）
CAHICHA: Computer Automated Hardware Interaction test to tell Computer and Humans Apart
Centre of Excellence, Artificial Intelligence & Robotics (AIR), School of Computer Science and Engineering VIT-AP University（VIT-AP大学计算机科学与工程学院人工智能与机器人卓越中心）；DigitalFortress Private Limited（DigitalFortress私人有限公司）；Centre of Excellence, Artificial Intelligence & Robotics (AIR), Department of CS (Cyber Security), School of Computer Science and Engineering School of Engineering, VIT-AP University（VIT-AP大学工程学院计算机科学与工程学院网络安全系人工智能与机器人卓越中心）；Dayananda Sagar University（达亚南达萨加尔大学）
