PRF extension

[jogemu]

Once the PRF extension is widely available for passkeys user may choose to encrypt their files using their passkey. Fetches in the scope of a service worker can encrypt files before sending them to the server and decrypt files between receiving them and browser parsing.

The user may choose to cache the encryption key in the service worker instead of requiring passkey assertion all the time. Unless explicitly requested otherwise, an intermediate encryption key encrypts the actual file. Meanwhile, the passkey is used to encrypt the intermediate key, allowing multiple passkeys/users to read/write the same file.

Based on step 1 of a blog, I came to the conclusion that Windows and Android do not yet support PRF. Apple seems to support PRF according to the documentation.