University researchers developed a way to encode hidden messages using the silent portions of a Skype call. Read More ..
Since Skype transmits voice data using 130-byte packets and silences in 70-byte packets, researchers at the Institute of Telecommunications of the Warsaw University of Technology were able to hide a message using structured sequences of silent packets, according to a report in the New Scientist. Wojciech Mazurczyk, Krysztof Szczypiorsk, and Maciej Karaœ built the SkypeHide (also known as SkyDe) application to demonstrate their technique. The application on the sending computer encodes a message in the silent packets in the call's data stream.
The application on the receiving computer reads the smaller data packets to extract the message. Hidden messages can contain text, audio or video content, so long as the total message does not exceed the maximum transmission rate of 1kbps.