When you need to send confidential documents to someone else than steganography can be an effective technique. Use SteganPEG to embed your files inside JPEGs, say, then just email them as normal, and casual observers will see only normal pictures. They’ll never realise your hidden data is inside.

And at first glance, DeepSound seems to carry out much the same function, but with audio files. Point the program at a WAV or FLAC file, hide a few personal documents inside, and you’re done: the audio files will still play just as before, and only someone who knows the secret will be able to extract your hidden content.

DeepSound does have one interesting twist, though. The program can read and extract hidden documents from within audio CD tracks, another level of indirection which makes it even less likely that your data will be spotted.

The interface has its drawbacks, but once you understand the basics DeepSound is easy enough to use

Making this happen is a little more complicated than it should be, in part because of DeepSound’s slightly odd design. When browsing for the carrier file, say, we expected to see a standard two-pane interface, with folders to the left, files to the right. But no, for some reason the developer has decided to display both files and folders in a single pane, an awkward approach which forced us to do a vast amount of scrolling.

Another issue is that DeepSound can’t burn the audio CD itself, so you’ll need another tool to do that. And you’ll have to ensure that it won’t manipulate the source files in any way, perhaps by normalising them or applying some other effect. In Windows Media Player, for example, we had to click “More burn options” and disable “Apply volume levelling across tracks”.

Once you understand these issues, though, the core DeepSound steps are simple enough. Browse to and click on a FLAC or WAV file; add whatever files you’d like to conceal; click Encode (optionally enabling “AES Encryption” and entering your passphrase), then burn the resulting file to CD.

Pass on the disc to whoever you like, and all they have to do is open the appropriate track (or tracks) with DeepSound. They’ll be prompted for the passphrase, if necessary, before your hidden content is extracted to the specified folder.

There’s plenty of room for improvement, then, and we wouldn’t want to use DeepSound to work with a large number of files. But if you only want to conceal a few documents, and you like the idea of using an audio CD carrier, then the program is certainly worth a try.