The movie “Contact” (1997) deals with this, plus lots of drama to make it commercially viable entertainment. The first step is that the signal is bursts of “noise”, clustered in groups of 1, 3, 5, 7, 11, 13, … 137(?) bursts, then repeating. The sequence convinces the team that it’s not a natural phenomenon. Then they discover an old signal from earth embedded, like your idea of playing back part of the other entity’s identifier. Then discovery of how some more images are coded, then how the images go together, etc. Not a lot of math, but… Based on a story “Contact” (1985) by Carl Sagan and Ann Druyan. — Mike On 31 Oct 2018 at 7:32, Henry Baker wrote:
I've been thinking about the following problem for a while, and hope that others have also.
The problem is: how do you establish communication with someone you don't know, and someone who doesn't speak the same language ?