THE internet’s underlying technology can be harnessed to let people exchange secret messages, perhaps allowing free speech an outlet in oppressive regimes.
Web, file transfer, email and peer-to-peer networks all use TCP, which ensures that data packets are received securely by making the sender wait until the receiver returns a “got it” message. If no such acknowledgement arrives (on average 1 in 1000 packets gets lost or corrupted), the sender’s computer sends the packet again. This scheme is known as TCP’s retransmission mechanism - and it can be bent to the steganographer’s whim, says Mazurczyk.
Their system, dubbed retransmission steganography (RSTEG), relies on sender and receiver using software that deliberately asks for retransmission even when email data 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,” he says in a preliminary research paper (www.arxiv.org/abs/0905.0363). So the message is hidden among the teeming network traffic.
noting both the yin and yang of futurity, watching cover ups as they happen, fighting back, and wooking pa nub in all de wong places. that's what i do.
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[the Other Outpost]
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