Snowden's comments were made during an interview on the 'StarTalk' podcast of astrophysicist and science communicator Neil deGrasse Tyson.
The whistleblower was speaking from Moscow via a robot video link called a "beam remote presence system." Controlling the robot from Russia, he was able to roll straight into Tyson's office at the Hayden Planetarium in New York.
JUST POSTED: Hero or Traitor? @StarTalkRadio's exclusive "Conversation w/ Edward Snowden." On iTunes & http://t.co/nLhC3fBsYa— Neil deGrasse Tyson (@neiltyson) September 19, 2015
When Tyson asked Snowden if a highly intelligent alien civilization might be communicating with encrypted messages, Snowden began by saying that most advanced societies realize they need to encrypt their communications, and that this could be the reason why we've never heard from other civilizations.
"If you have an 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 when all their communication will be sent via the most primitive and most unprotected means," Snowden said.
"So when we think about everything that we're hearing through our satellites or everything that they're hearing from our civilization (if there are indeed aliens out there), all of their communications are encrypted by default."
He added that encryption would render communication indistinguishable from "cosmic microwave background radiation."
"If you look at encrypted communication, if they are properly encrypted, there is no real way to tell that they are encrypted,"Snowden said. "You can't distinguish a properly encrypted communication from random behavior."
Snowden is less famous for his views on extraterrestrials and more so for leaking classified documents which revealed the US government's secret mass surveillance program. The whistleblower now resides in Russia, where he was granted asylum after Washington charged him with theft and espionage.
Comment: Maybe during Snowden's stint with the NSA he learned a lot more about the Extraterrestrial presence here than he's letting on, and wants to seem circumspect on the subject so as not to detract from his main message? Then again, this bit of data may be all he really knows.
Whatever the case may be, there are a whole slew of reasons why humanity has been largely kept in the dark about this subject of subjects.
See: Fermi's phony paradox: Humans too arrogant and stupid to solve 'missing aliens' question