Edward Snowden, the former contractor who leaked National Security Agency secrets publicly in 2013, is now getting attention for an odd subject: aliens.

In a podcast interview with astrophysicist Neil deGrasse Tyson, Snowden suggested that alien communications might be encrypted so well that humans trying to eavesdrop on extraterrestrials would have no idea they were hearing anything but noise. There’s only a small window in the development of communication in which unencrypted messages are the norm, Snowden said.

“So if you have an alien civilization trying to listen for other civilizations, or our civilization trying to listen for aliens, there’s only one small period in the development of their society where all of their communications will be sent via the most primitive and most unprotected means,” he said.

But those holding out hope for contact from extraterrestrials can breathe easy: Humanity’s current search for alien intelligence doesn’t rely on an intelligible message, say scientists with the SETI Institute, which is dedicated to the search for life in the universe. The real hunt, they say, is for the medium.

“We’re not looking for the message,” said Seth Shostak, director of the SETI Institute’s Center for SETI Research. “We’re looking for the signal that tells us that somebody has a transmitter.”

Signal received
To be fair, Snowden was speaking off-the-cuff about encryption in general; it’s not likely he expected to be chatting about aliens or has done an in-depth study of how the search for extraterrestrial intelligence has evolved.

But data encryption is beside the point, Shostak said. So far, most of the hunt for alien signals has used radio waves, based on the theory that radio is a relatively easy and cheap way to send signals a long way through space.

The SETI Institute uses powerful radio telescopes on Earth to search for narrow-band signals, or signals focused at one spot on the radio dial, Shostak said. Lots of natural bodies make radio noise, he said, but the only thing that makes a narrow-band signal, as far as scientists know, is a transmitter.

Thus, a focused band of signal is a waving flag, signaling, “Hey, there’s somebody out there who can build a radio transmitter,” Shostak said. The message itself might be indistinguishable from noise if it were well encrypted, but it would still, obviously, be a message.

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