This post shows step by step how to create an encrypted disk image. The Disk Image utility is a pre-bundled application, sold with every copy of Mac OS X Tiger (10.4). Popular pre-sized images, such as CD,DVD (4.7 GB), DVD (8.0 GB) can also be burned, making this a good technique for backups, particularly if you have sensitive information on them.
The encryption used is AES-128 bit, which is very strong. A brute force key decryption attempt, even with large clusters of latest/greatest supercomputers, would still take beyond any of our lifetimes. Do not lose the key as their is no way to get the data back!!!!
Disk Utility is a handy app, though powerful. You can do many useful things with this application, including accidentally erase a hard drive, so be careful. It will warn you before you do anything, but be aware of it’s powers.
