[kfreds]

Tillitis Key’s design encourages developers to experiment with new security key applications and models in a way that makes adoption easier and less risky for end-users.

You can read more on tillitis.se or in the comment I made below.

Tillitis Key will allow you to chain-load applications. This means that you could have a thin loader which does code signing verification of the next application stage, and hand off the secret to it. Basically it's a trust policy that defines under what circumstances the next application stage gets the secret.

Another trust policy the loader could have is requiring m-of-n code signatures, or perhaps that as well as transparency log inclusion. Check out sigsum.org.