This weekend I had reason to want to encrypt some files on my Mac. As well as my iCompta files, iCompta is a brilliant open source app for tracking finances, I also had some passwords in a text file. I don’t know what the passwords are for, but know that I must have considered them important at some point and if I delete the file then I will discover it’s secret about five seconds later.
So, how to encrypt them? Stick them in a folder and fire up Disk Utility. What? You don’t have a Mac?!? Cry me a river, I don’t care about Windows or Linux. Go on… get out of here. Good, they’re gone. Select the “new disk image from folder” option and select read/write and 256 bit encryption. Choose a password (don’t save it in your keychain – duh!).
You should now have a disk image that cannot be mounted without your password and will keep all of your files safe and sound (as long as you don’t leave it mounted permanently – duh!). Although this worked *almost* perfectly for my requirements (there are issues with Time Machine), I’m not sure of the implications of this approach on disk fragmentation, so if you are going to do this on large a file system, you might want to investigate further.