The Sounds of Silence on Skype Hold More than Expected Thanks to Polish Discovery

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The Sounds of Silence on Skype Hold More than Expected Thanks to Polish Discovery

January 07, 2013

Silence carries with it a lot of connotations for people: loneliness, tranquility, peacefulness, isolation. Some people crave silence. Others can't stand it. But for a professor at the Warsaw University of Technology, Wojciech Mazurczyk, the sound of silence could be carrying volumes of useful data that even the FBI couldn't overhear.

The concept may sound outlandish--encrypting messages in silence?--but as it turns out, it makes quite a bit of sense. What Mazurczyk realized is that, when Skype detects silence, it doesn't send anything at all, but rather packets measuring, universally, 70 bits. When no one's talking, Skype sends these 70 bit packets, but Skype itself does nothing to decode them. Mazurczyk, backed up by a team of researchers, discovered that there was in fact a way to intercept and decode these 70-bit packets. With that knowledge in hand, adding information to those 70-bit packets became a much easier concept, allowing Mazurczyk and his team to add information to silence in a conversation. Mazurczyk will be presenting the results of his team's findings at a steganography conference in France this summer.

But the implications of this likely aren't sitting well. Skype spokesmen are, reportedly, in conference with their chief security officer before issuing a comment on these findings. Various government agencies in the United States and beyond are trying to get approval to listen in on Skype calls, and having to monitor each call--including the 70-bit silence packets--would be a daunting task even for a government agency. Though there are patents already in the works that allow eavesdropping on Skype calls, including VoIP-Pal's "Lawful Intercept" and Microsoft's "Legal Intercept", there's little word on whether these programs could pick up the content from the Skype silence packets.

Given that Skype's terms of service already allow for plenty of cooperation with government figures, and that software is currently in the works to facilitate that eavesdropping, it's not surprising to see security researchers looking for ways around that push for more government access to communications. Whether that research will be used for nefarious ends or not is unknown, though there will likely be plenty who try to do just that, especially as the rise of mobile VoIP sends even more users into Skype's bailiwick.

The issue of privacy versus the need of law enforcement to have information is a thorny one indeed, and one that will likely be hotly debated for some time to come. For every development in one side of the issue, there is likely to come a nearly equal development from the opposite side of the issue to counteract the reach of the first. Whether Skype's silence will speak against it or not remains to be seen, but the constant back and forth this issue engenders isn't likely to stop any time soon.

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Edited by Brooke Neuman

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