https://twitter.com/GrapheneOS/status/1342307913440907265
android.googlesource.com/platform/frame… is the place to start if you're interested in finer details of the implementation.
For Pixel 2 and later, isWeaverAvailable() is true.
SyntheticPasswordCrypto.personalisedHash(...) is used to quickly derive a value with SHA-512.
For example, the Weaver key is made by passing "weaver-key" and the password token to SyntheticPasswordCrypto.personalisedHash(...). That way, the password token derived with scrypt isn't actually sent to the secure element. That's used for deriving a bunch of different keys.
There's also other hashing that's not really noteworthy such as the lockscreen implementation hashing the password in a similar way before passing it along, etc. The actual work factor is provided by scrypt and the SoC-specific hardware-accelerated, hardware-bound key derivation.
Focusing on the important aspects in the FAQ section. Skipping over how it works on devices without Weaver and user profiles without a password also helps keep things simpler. Devices without Weaver use personalisedHash of a 16kiB randomly generated file to help with wiping keys.
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