Free open source on-the-fly encryption software
Never create a new TrueCrypt volume by cloning an existing TrueCrypt volume. Always use the TrueCrypt Volume Creation Wizard to create a new TrueCrypt volume. If you clone a volume and then start using both this volume and its clone in a way that both eventually contain different data, then you might aid cryptanalysis (both volumes will share a single key set). This is especially critical when the volume contains a hidden volume. Also note that plausible deniability (see section Plausible Deniability) is impossible in such cases. See also the chapter How to Back Up Securely.