Secret messages could be hidden in net phone calls
02 June 2008
Paul Marks
Magazine issue 2658

THE next time your internet (VoIP) phone call sounds a bit fuzzy, it might not be your ISP that's to blame. Someone could be trying to squeeze a secret message between the packets of data carrying the caller's voice.

Wojciech Mazurczyk and Krzysztof Szczypiorski, information scientists at the Institute of Telecommunications in Warsaw, Poland, revealed last week that they are developing a "steganographic" system for VoIP networks (www.arxiv.org/abs/0805.2938). Steganography is the art of hiding messages by embedding them in ordinary communications. For example, a message can be encoded as a string of numbers which are used to modify the brightness and colour of an image. The effect is too subtle to be noticed by unwitting observers but the message can be deciphered with appropriate software by anyone who knows it's there.

Now the Polish researchers have worked out how to use internet phone calls rather than images as ...