IN THIS CHAPTER
Understanding how encryption works
Protecting individual documents with encryption
Storing data safely on encrypted disk images
Encrypting your home folder with FileVault
Using third-party software to encrypt your entire startup disk
Deleting files so they can't be recovered
Overwriting free space on your hard disk
Recovering previously deleted files
As long as your Mac is under your sole control, it's perfectly fine for all your files to be stored on your hard disk in their normal state — freely viewable without any special procedures. Unfortunately, it's difficult for anyone to guarantee that no one else will ever have physical access to his or her computer. There are the obvious cases — such as theft, a nosy roommate or co-worker, or a network intruder who has gained access to your disk — in which your data could slip from your control. But there are other situations that can affect even the most scrupulous and security-conscious person. What if your Mac breaks down, for example, and you need to take it in for servicing? An unscrupulous repairperson could read anything on your disk.
It's fair to ask whether that would even matter. Some people keep very little confidential information on their Macs, so it wouldn't be a particular problem if someone else gained access to it. At the other end of the spectrum, if your hard disk contains your company's business secrets, classified government information, or your patients' ...