Catch up on stories from the past week (and beyond) at the Slashdot story archive


Forgot your password?
Check out the new SourceForge HTML5 internet speed test! No Flash necessary and runs on all devices. ×

Submission + - Phony TCP Retransmissions Can Hide Secret Messages 2

Hugh Pickens writes: "New Scientist reports that a team of steganographers at the Institute of Telecommunications in Warsaw, Poland have figured out how to send hidden messages using the internet's transmission control protocol (TCP) using a method that might help people in totalitarian regimes avoid censorship. 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 in a system known as TCP's retransmission mechanism. The new steganographic system, dubbed retransmission steganography (RSTEG), relies on the 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," says Wojciech Mazurczyk. "The sender then retransmits the packet but with some secret data inserted in it." Could a careful eavesdropper spot that RSTEG is being used because the first sent packet is different from the one containing the secret message? As long as the system is not over-used, apparently not, because if a packet is corrupted the original packet and the retransmitted one will differ from each other anyway, masking the use of RSTEG."

Slashdot Top Deals

To write good code is a worthy challenge, and a source of civilized delight. -- stolen and paraphrased from William Safire