@tychotithonus well, its hard to say it is proper key :) Just wanted something better, than (at that moment) keeping ssh keys with weak crypto on disk. Also i was inspired by much more advanced project:
https://www.fsij.org/doc-gnuk/intro.htmlAt one side MCU based keys are no match special crypto hw, at another side i have feeling each specialized crypto hw have undisclosed backdoor(s) :)