

In this theoretical system, ideally it’s illegal for anyone other than the person who’s supposed to have the private key to have it - excepting some subset of legal reasons (e.g. parents for their children). So, the only business that would be asking for people’s private keys are the kind that are already operating outside of the law.
Impeachment proceedings are not judicial proceedings; they’re political ones. Both processes use similar language because the process is similar, but they are not connected. Commission of a crime is not required for impeachment proceedings and being impeached by the House and convicted by the Senate conveys no criminal punishment.