
First the researchers noted that even when there's silence in a Skype call, the software is still generating and sending packets of audio data. After analyzing Skype calls, they found that they could reliably identify those silence packets, because they were only about half the size of packets containing voices. SkyDe (for Skype Hide) encrypts your hidden message, grabs a certain portion of outgoing silence packets, and stuffs the encrypted message into them. (more)
Important point: Conventional steganography hides data within photos and pictures. Downside... Your hidden message may languish on servers in multiple places for a long time, where it could eventually be discovered. Sky-De reduces this vulnerability. ~Kevin