Mac® Security Bible

13.2. Encrypting Individual Files and Folders

The most basic approach to encryption is to apply it only to the particular items that are especially sensitive. Although it would be extremely awkward to individually encrypt each file you use on a daily basis, encrypting specific files or folders makes sense when sending the info over the Internet (by email, FTP, or otherwise) or if you're using any other unencrypted transmission or storage method, such as employing a flash drive, external hard drive, or optical disc to move files from one location to another.

As mentioned earlier in this chapter, it's important to remember that when you encrypt a file or folder, you actually create an encrypted copy, leaving the original intact and unencrypted. The same is true if you decrypt a file or folder, modify it, and then re-encrypt it. Therefore, the safest practice to follow after encrypting something is to securely delete the original; for example, by dragging it to the Trash and choosing Finder Secure Empty Trash.

If this is the sort of encryption you want, you have many tools to choose from. Mac OS X includes command-line utilities that can encrypt files (as described in just a moment), although they're not terribly convenient to use. Numerous third-party vendors offer easy-to-use alternatives, with a wide variety of encryption algorithms, interfaces, and extra features. Regardless of ...