Yung-Hsing and my interests have, historically, converged now and again, but it would appear that her recent interest in code-breaking — I turned her onto the _Bletchley Park_ series available in Netflix — has brought us together again. For her, I link to [this page] that has the PDF templates to create your own enigma machine using paper rotors — taped rings os paper wrapped around a cardboard tube.
Begin with an article on [steganography](http://arstechnica.com/business/news/2012/05/steganography-how-al-qaeda-hid-secret-documents-in-a-porn-video.ars). Follow link in comments to famous case of a [musician embedding an image in the spectrogram](http://www.youtube.com/watch?v=u-KMFxzA_Lk&t=5m30s) of a work. Discover that there are programs which will [do this](http://www.uisoftware.com/MetaSynth/index.php).