Hi,

I don't know anything about SQL Server or Windows, but I would be surprised if there wouldn't be a way to enable authentication over secured connections.

The Unix way to solve this problem would be to tunnel the connection over SSH. This is what I do when MySQL or PostgreSQL are bound to the loopback interface without open ports to the outside. You connect to the server with SSH, and the SSH daemon on the server would then forward the connection locally to the right port where SQL Server is running. I'm sure there are versions of SSH for Windows, and perhaps Putty can listen for connections in a server sort of way. I'm sorry I can't help you more – I know nothing about Windows software – but this is one way you might be able to make it work in a secure manner.

Good luck!