somewhere around 2013 (and precisely - for ‘small’ Santa Claus, so 6th of December), OpenSSH was extended to provide new way of storing keys.
it’s important because the old format - MD5 hash - can be cracked veeeeery quickly. developers decide to use modification of bcrypt, that will slow down GPU-assisted cracking attempts in hashcat from gigahashes per second, to at most kilohashes.
what you need to do to upgrade your defenses?...
working remotely on Windows via Remote Desktop if you’re hanging off GRPS or 3G connectivity somewhere in the mountains (for example) isn’t optimal. as I had to access some such servers remotely.
you can find cygwin useful (there’s also VanDyke V-Shell, a bit pricey and for non-commercial use). cygwin package installs UNIX environment, and that - yes - may include OpenSSH plus some tools (like scp for example)
you just need to download, and then run installation, selecting cygrunsrv and openssh....