I would like to store a few folders of sensitive financial data on DropBox for easy access while on the road. I already use a VPN to keep the coffee-shop hackers at bay, but I worry about security on the DropBox end of things. My current thought is simply to make an encrypted .dmg file of the folders via Disk Utility and park that on DropBox -- but I also see people using specialized programs such as Boxcryptor. Is there any particular advantage to one approach over the other?