I like learning new words. Especially ones that have multiple connotations. The word Steganography is a great example of this. I came across this word when I was reading around security techniques and variations on cryptographic techniques. The discussion veered into security and varying techniques of hiding a content of a message. As the dictionary definition states the "Art of Steganography is the art and science of writing hidden messages in such a way that no one apart from the intended recipient knows of the existence of the message; this is in contrast to cryptography, where the existence of the message itself is not disguised, but the content is obscured". Examples of old steganography techniques are, writing on a shaved head,(then letting the hair grow !), invisible ink, microscopic images. So how does this affect the digital medium. The use for it digitally is as follows , Steganography replaces unneeded bits in image and sound files with secret data. So steganography hides the very existence of the data. And it's much more difficult to detect under traditional traffic-pattern analysis. For a great article on this go to securityfocus. Comprehensive information can be found on fabien petitcolas site. These web site talk about the "good" parts of steganography. For example Digital Watermarks especially important if you are copywriting materials. This is an example of where Steganography techniques are not used to hide material but to fingerprint it. So you are providing resilience against attempts to remove the data and copy it and claim it as your own. However where it gets really interesting are the illegitimate uses !. Here a whole new world opens up. Again on the Securityfocus web site it provides examples of embedding a message within a JPEG image. Also peticolas web site gives some great information on embedding messages within mp3 files and some great accompanying tools. This is going to be an interesting arena to keep one eye on especially in the arena of digitally copyrighting music. Just think there now is the technology and potential to incorporate functionality that if an mp3 or WAV file was obtained illegally, the player would recognize this and refuse to play it. This plus many other security and steganography related subjects has been discussed in depth by John DeTreville who is a Senior Researcher at Microsoft Research.