Write up our scheme for using Secret Storage to save old SS keys
For whatever reason, Matrix doesn't have an official mechanism in the spec for saving Secret Storage keys.
For Circles and Matrix.swift, we have invented a simple scheme for saving these keys as secrets themselves, encrypted under another (usually, newer) key in Secret Storage.
I need to write up our scheme in sufficient detail that @taras.smakula can implement it in Android, and then I need to propose it as an MSC for inclusion in the Matrix spec.