This blog post outlines recent improvements around how users interact with the lockscreen on Android devices and more generally with authentication. The team focuses on ensuring that Android devices respect the privacy and sensitivity of user data. In particular, we focus on two categories of authentication that present both immense potential as well as potentially immense risk if not designed well: biometrics and environmental modalities. The model itself is fairly simple, classifying authentication modalities into three buckets of decreasing levels of security and commensurately increasing constraints. The primary tier is the least constrained in the sense users only need to re-enter a primary modality under certain situations (for example, after each boot or every 72 hours)”]
Source: https://security.googleblog.com/2020/09/lockscreen-and-authentication.html