I normally wouldn’t make any sort of mention of porn … not even in jest … but this site uses it as just one example of the sort of information that might reside on your computer that you probably want to keep out of the hands of others. All of the techniques have a number of other uses.
For instance, I use TrueCrypt to securely store client accounting files in an encrypted directory and Eraser to delete other files existing outside the encrypted directory. This muddies the waters about the boundaries of the encrypted directory(ies). I do this so that I won’t get in legal hot water from my clients if the computer itself should be stolen. As long as I have physical custody of the (separately encrypted) USB drive and access to a fresh copy of TrueCrypt, the client data is safe and recoverable. If the USB drive is also stolen, I can still assure the client that no one can read the files. Not in this life, anyways … and maybe not in the next, either.
You can use any sort of file as the source of the encryption seed … even those .jpg files from the darker corners of the internet or those torrent download audio files that you’d just as soon no one knew you had. You might also take the output from a random number generator to use as a keyfile. Just copy and paste from the website to a text file. Save the text file using any name and any extension (Jillian_in_black.png, for instance or “TheWall_trk01.wav” or “2008q3.xls”) and tell TrueCrypt to use the file as a keyfile when encrypting or decrypting. Or, make a file like this as ‘bait’ and use a REAL photo, audio or ‘whatever’ file for the encryption seed.
Then, too, there is the issue of personal privacy. For several years now, technology has outstripped legislation so that there really IS no reasonable assurance of privacy anywhere. It is up to the citizen / end user to enforce their claim on privacy or lose it to ‘un-named others’. Just because I have ‘nothing to hide’ doesn’t mean that others get to gawk at it.
So, if you are interested in preserving your (US) constitutional rights to privacy, get on over to http://virtualhosting.com/blog and give them a thorough read. Just don’t tell ‘em that I sent ya, okay?