This week, Jeff wrote in to ask whether we would be able to recognise and understand an encrypted message from space. Emma Sackville enlisted Dr. Duncan Forgan from the University of St. Andrews to help decode this question...
Well, it depends. If the encryption is really good, it might not be distinguishable from thermal noise or cosmic microwave background radiation. But for keeping TV signals from nonsubscribers, that is not necessary. You can still have an identifiable carrier frequency. That sort of thing would be easily detected, even if not decipherable. This assumes, of course, that an alien signal would use principles that we would. That is, however, not necessarily assured, and they could choose some peculiar broadband method, for example, that might not be recognizable by our equipment. Atomic-S, Fri, 8th Apr 2016
Claude Shannon was a pioneer of information theory - how to communicate efficiently.
One way to differentiate a signal with noise versus one with information is to take a histogram of if its "bits".
Advanced Aliens would probably communicate by modulating gravity waves so no we wouldn't be able to listen with our primitive radio dishes. d4rr3n, Thu, 12th May 2016