[skywhopper]

I can see how this might seem convenient, but using this service would be a really bad idea. The vendor even seems to know this:

    Sharing your public key is ok, but you should never
    share your private key (from the file id_rsa) with
    anyone. Instead, we've made it easy to create new
    Shellvault-specific keypairs.

Unfortunately, this only means that Shellvault creates the private key itself. Which amounts to "sharing your private key".

The lack of an end-to-end encryption tunnel means that despite the vendor's best intentions, this service introduces a lot of points at which a malicious actor (or accidental misconfiguration) could compromise your session.

In short, there are multiple good, free, native, and local SSH clients and terminal emulators for every platform. Use those instead.