TrueCrypt is really astonishingly wonderful piece of cryptographic software and unfortunately and ironically for me it is too good at what it does.
TrueCrypt is a free and open source utility that performs on on-the-fly encryption allowing the user to create a virtual encrypted disk (TrueCrypt volume). TrueCrypt can either create an encrypted file that acts as a real disk or encrypt an entire hard disk partition or a storage device/medium, such as floppy disk or USB memory stick.
One of the best features of the TrueCrypt software is that allows you to use passwords based upon the content of files. So you designate one or more files as keyfiles and it combines that with the password you type in to create an ultra-secure unbreakable password. So say you choose the password Gazza after your favourite footballer of the 90s this would be a trivial password for a brute force attack to crack but if you were to combine it with a keyfile of an MP3 of Fog On The Tyne then it would become immeasurably more difficult.
However should you ever lose the keyfiles that you chose to use or like me forget which ones that you used the TrueCrypt volume that you have created becomes impossible to open and you lose all the data you have so carefully secured.
Luckily for me the drive that I had encrypted was merely used to back up important data for my publishing business and so I didn’t lose anything but the time it took to reformat the disk and back up all my business data yet again.
I do wonder what would have happened should I have been compelled to decrypt the volume under Part III of the Regulation of Investigatory Powers Act 2000 as clearly I really could not have done so.