[abpavel]

This looks like reincarnation of "Lock & Key" feature of Cisco routers available since the late 90s. There were two major issues that led to abandonment and hindered adoption. The first is that it's an extra step. Extra steps for installation, for complexity, for single point of failure, for availability of key services. The second is that instead of thwarting attackers, you're thwarting yourself, every single time. It breaks so many usecases, for example if you have a new machine, or if you want to access through a jump host, or from ssh client on phone, etc.