This chapter covered ways of keeping others from reading private data stored on your hard disk. I outlined the basic concepts of encryption, along with common pitfalls and misunderstandings. I then reviewed several third-party applications that can encrypt individual files and folders. To make it easier to encrypt and decrypt numerous items at once, an encrypted disk image is often a better choice; I explained how to create and use these with both Disk Utility and PGP.
I next covered FileVault, which uses a special encrypted disk image to store the contents of a user's home folder. When even that is insufficient, you can encrypt an entire volume — even your startup volume — using any of several third-party utilities. After you encrypt files (or when you delete unencrypted files), their original, easily readable data can remain on your disk unless you take special steps to overwrite them so they can't be recovered. I described how to do this and mentioned steps you should take when getting rid of an old Mac or media.
I wrapped up this chapter by demonstrating how to recover deleted files that haven't been overwritten to illustrate the importance of secure deletion.