Explore a conference talk from CCS 2016 that delves into the security vulnerabilities of public WiFi networks and their potential to compromise mobile phone passwords. Learn how researchers from Shanghai Jiao Tong University, University of Massachusetts at Boston, and University of South Florida investigate the use of Channel State Information (CSI) to infer sensitive data input on mobile devices. Discover the attack scenario, challenges, and system design of this novel approach, including ICMP-based CSI collection, sensitive input module, data preprocessing, and password inference techniques. Examine the classification methods used to distinguish between different numbers and infer 6-digit passwords. Gain insights into the influence factors, limitations, and implications of this research for online mobile payment security and WiFi-based recognition systems.