The Internet's underlying technology can be harnessed to let people exchange secret messages, perhaps allowing free, coded speech under oppressive regimes. So says a team of steganographers at the Institute of Telecommunications in Warsaw, Poland. Steganography is the art of hiding a message in an openly available medium.
The system, dubbed retransmission steganography, relies on sender and receiver using software that deliberately asks for retransmission of TCP email data packets even when the packets are received successfully. "The receiver intentionally signals that a loss has occurred. The sender then retransmits the packet but with some secret data inserted in it," says research assistant Wojciech Mazurczyk in a preliminary research paper.
From New Scientist
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