Implicit authentication (IA) is gaining popularity over recent years due to its use of user behavior as the main input, relieving users from explicit actions such as remembering and entering passwords. However, such convenience comes with a cost of authentication accuracy and delay which we propose to improve in this paper. Authentication accuracy deteriorates as users' behaviors change as a result of mood, age, a change of routine, etc. Current authentication systems handle failed authentication attempts by locking the users out of their mobile devices. It is unsuitable for IA whose accuracy deterioration induces a high false reject rate, rendering the IA system unusable. Furthermore, existing IA systems leverage computationally expensive machine learning, which can introduce a large authentication delay. It is challenging to improve the authentication accuracy of these systems without sacrificing authentication delay. In this paper, we propose a multi-level privilege control (MPC) scheme that dynamically adjusts users' access privilege based on their behavior change. MPC increases the system's confidence in users' legitimacy even when their behaviors deviate from historical data, thus improving authentication accuracy. It is a lightweight feature added to the existing IA schemes that helps avoid frequent and expensive retraining of machine learning models, thus improving authentication delay. We demonstrate that MPC increases authentication accuracy by 18.63\% and reduces authentication delay by 7.02 minutes on average, using a public dataset that contains comprehensive user behavior data.

翻译：近年来,由于使用用户行为作为主要投入,隐含认证(IA)近年来越来越受欢迎,因为使用用户行为作为主要投入,使用户摆脱记忆和输入密码等明确行动。然而,这种便利带来认证准确性和延迟的成本,而我们提议在本文中加以改进。由于用户行为的变化,情绪、年龄、常规变化等等,认证准确性会随着用户行为的变化而恶化。目前的认证系统通过将用户从移动设备中锁住来处理认证尝试失败。对于IA来说,其准确性恶化导致错误拒绝率高,使IA系统无法使用。此外,现有的IA系统利用计算成本昂贵的机器学习,这可能会造成大量认证延迟。在不牺牲认证延迟的情况下提高这些系统的认证准确性是一件艰巨的任务。在本文中,我们提出了一个多层次的特权控制(MPC)计划,根据用户行为变化来动态调整用户的准入特权。MPC提高了系统对用户合法性的信心,即使其行为偏离历史数据,从而使得IA系统无法使用。此外,现有的IA系统还增加了一个较轻的特征特征特征,因为其计算费用昂贵的机器学习方法有助于避免经常和高价的认证。