• Drive encryption and file encryption: the difference
• The pros and cons of hard drive encryption
  

When it comes to protecting your external hard drives using encryption, you've got two options: external hard drive encryption and file encryption.  While I have already detailed the difference before, I might as well go a little more in depth.

"Hard drive encryption" (aka, full disk encryption) describes a case where the entire hard drive is encrypted.  It must be noted, full disk encryption does not actually encrypt your files.  Rather, the hard disk--and as a result, anything that is stored on that hard disk--is encrypted.

It sounds like the same thing, doesn't it?  After all, encrypted is encrypted, right?

However, there's a critical difference: if you copy the files off the external hard disk to another device--like to another external hard drive, another computer, or burn it to a CD, or send it via e-mail--your data will not show up as encrypted.  That's because the file has been released from the confines of the protected (encrypted) hard drive.

So, let me emphasize the point once more: under hard disk encryption, it's not the actual files that are encrypted; it is the external hard disk itself that is encrypted, and as a result, the files on that encrypted hard disk are protected as well.

"File encryption," on the other hand, does exactly what its name implies: the file itself is encrypted.  So copy, burn, and e-mail away: your information will be protected not matter what.

So why do people even bother with hard disk encryption?  There are pros and cons to everything, and hard disk encryption is no different. Some of the pros are:

• Anything that’s saved to the external drive is automatically encrypted.
• No need to wonder (or worry) if you forgot to encrypt a file, if you lose the external drive (see above bullet point).
• No need to worry about temporary files or cached files, which are created automatically whenever you work on a document.  Sometimes they're deleted after closing the document, sometimes they're not.  (More importantly, it's nearly impossible to encrypt temporary files one by one.  Keeping a Word document open for 10 minutes, for example, creates at least 10 temporary files alone.)
• If the hard disk is being used as a data backup repository, you know you're set in terms of data security.
• Easier auditing.  Since anything on the computer is encrypted automatically, all you have to prove is that the computer was encrypted prior to being stolen.

The cons?

• The situation I described above about copying files to somewhere else.
• There’s an initial period where you must encrypt your drive.  This process could take a couple of hours to half a day depending on your computer's specs (RAM, CPU, drive capacity, etc.) and the encryption algorithm being used.  However, companies like AlertBoot offer encryption solutions where the encryption process runs in the background and is barely noticeable (a "transparent" process), so it doesn't have as much of an impact as it would have 5 years ago.

Overall, disk encryption offers the same protection as file encryption with less hassles.  The frustrations you gain when copying files off the disk are neutralized by not having to worry about temporary and cached files--a real concern, since there are cheap (even free) products out there that will peer into such files for data mining purposes (Google desktop being one of them), a concern if you ever lose an external hard disk drive or a laptop computer.