extract function
Generates a pseudorandom key for use with expand from an input secret and an optional independent salt.
Only use this function if you need to reuse the extracted key with multiple expand invocations and different context values. Most common scenarios, including the generation of multiple keys, should use key instead.
Implementation
Uint8List extract({required Uint8List secret, required Uint8List salt}) =>
ffi.hkdfExtract(secret: secret, salt: salt);