[Cryptography] Secret Handshake problem.

[Joseph Kilcullen]

> Also known as the "Are you also a Soviet Spy?" problem.

More.... That is, you use Game Theory screening strategies and 
signalling strategies. Bluffing, dropping hints that an actual agent 
would pick up on, then screening strategies to seal the deal if he looks 
real. Its pure game theory.

This is my favourite screening strategy example: Page 186 of Game Theory 
at Work – Miller: When the Greeks came for him, Odysseus tried to dodge 
the draft by acting insane. He ploughed his field randomly. Since an 
insane Odysseus would be useless to their cause, almost all of the 
Greeks were ready to abandon Odysseus to his strange farming practices. 
One Greek, Palamedes, suspected that Odysseus was faking. Palamedes 
however, still needed to prove that Odysseus was sane, so he took 
Odysseus’s infant son and put him in front of the plough. Had Odysseus 
continued to plough, he would have killed his son. If Odysseus really 
had been insane, he would not have noticed or cared about his son’s 
position and would therefore have killed him. Since Odysseus was 
rational, however, he stopped ploughing and thus revealed his sanity.

So, for example, you might ask a plausible deniability , harmless, 
question which an actual agent would recognise, like referring to 
something in the Soviet KGB building that only an actual agent would 
know about. Like refer to the walls of the canteen being painted red as 
an odd choice, and see if the other guy raises an eyebrow and replies 
with another reference for you to reply to.

Another relevant example: It was a 'thing' when people not in the KKK 
found out the KKK handshakes etc. People who were not members of the KKK 
could make fools of them by pretending to be members. Stetson Kennedy 
going public with all their secrets effectively destroyed the KKK. See: 
http://www.dailymail.co.uk/news/article-2030896/Klan-buster-Stetson-Kennedy-exposed-Ku-Klux-Klans-secrets-dies-aged-94.html

lol... a good example. You might know all about this stuff. You might 
have posted this to see who else, out there, knows all this game theory 
stuff. When I replied to this message bingo, you got me. A screening 
strategy to elicit 'who else out there knows this stuff?'

J