I've been reading about the encryption features of TrueCrypt, including the feature to have an encrypted volume inside a file with any name. For example, I can create an encrypted volume inside a file named music.mp3. However, the file won't really play when I try to open it in a music player. Is there a way to add "decoy" content to music.mp3 so that someone who doesn't know its got encrypted content can double click on it and music will play? Obviously it doesn't have to be music, but also images, decoy test document, etc. etc. If TrueCrypt can't do this, is there another piece of encryption software that can? Thanks!
This may not be a definitive answer to your question, but you might consider looking into TrueCrypt's Hidden Containers feature. I don't believe TrueCrypt allows specifying an encrypted container at an offset within a file (at least not now). Not to mention, it would look suspicious to have a very large "valid" file with very small valid "content".