Research has shown that counting WiFi packets called probe requests (PRs) implicitly provides a proxy for the number of people in an area. In this paper, we discuss a crowd counting system involving WiFi sensors detecting PRs over the air, then extracting and anonymizing their media access control (MAC) addresses using a hash-based approach. This paper discusses an anonymization procedure and shows time-synchronization inaccuracies among sensors and hashing collision rates to be low enough to prevent anonymization from interfering with counting algorithms. In particular, we derive an approximation of the collision rate of uniformly distributed identifiers, with analytical error bounds.

翻译：研究表明，通过统计被称为探测请求（PR）的WiFi数据包数量，可间接作为区域人群数量的代理指标。本文讨论了一种人群计数系统，该系统通过WiFi传感器空中捕获探测请求，并采用基于哈希的方法提取并匿名化其介质访问控制（MAC）地址。本文阐述了匿名化流程，并论证了传感器间的时间同步误差及哈希碰撞率均足够低，不会对计数算法的正常运行产生干扰。特别地，我们推导了均匀分布标识符碰撞率的近似表达式及解析误差界。