There’s a pretty slick way to password protect files and folders on your computer, so, even if you’re logged in, you have to enter a password to get access to the files.
The first question you might ask is, why would you want to do that? When you log in as your user, you can restrict the read/write access to any file or folder, you can make a separate user to keep your files separate (and inaccessible) to another user, right? …but suppose you want an extra measure of security. Either you occasionally leave your computer unattended, or you’re using a public workstation like an internet café or a school computer lab, or maybe you simply want to safeguard files on a jump drive in case the drive gets lost.* Here’s how to do it.
What you’re going to do is to make a “Disk Image”, which is a file that contains the complete directory information and structure of a storage device like a hard drive or CD or DVD, but it's actually just a file. When you open it up, it looks like a new drive on your desktop. When you make it, you’re going to encrypt it, and it will ask you for a password every time you try to open it. Once you put your files into the disk image, you can move it, copy it, even delete it, but you can’t get into it without the password.
To do this you use the “Disk Utility” in the Applications>Utilities folder. Start it up, and go right to File>New>Blank Disk Image. That will open up a window that asks for the Name (Save As:_________), where to save it to, the Size, Encryption and the Format.
For the location, you can make it even more secure if it’s not readily visible, so the Desktop probably isn’t the best place, nor is the “Documents” folder. Put it some place weird, but that you can find. Set the Size to the smallest size that will suit your needs. This Disk Image will lock up that space on your hard drive, so don’t be excessive here. Select AES-128 Encryption, and make sure the Format is set to read/write disk image.
The next window will ask you for a Password. Make sure you remember this password, and make sure you UNCHECK the “Remember password (add to Keychain) box. This will then build a file called (name).dng. To get into it, just double-click it. It will then ask you for the password. From there you can just drag and delete files in and out of it, but once you close it you need the password to get back in.
As with any lock, this helps to keep honest people honest… and you certainly don’t want to keep your only copies of files in there. It’s no substitute for other good security practices, and has to be used responsibly in your backup routines, but, for that little bit of extra safety, it’s a neat little trick.
*I personally have found several lost jump drives around… WITH very personal information! Luckily, I was able to use that information to find and return the drives to their owners, but… imagine the risks! By the way, it’s a good idea to put a “return to owner” text file on any jump drive, with some basic contact information like an email address, just in case…
