 The title that I wanted was called Stop Cheating but this is not very informative so the serious title is this long, long one. So when we talk about collusion in real life we talk about games and specifically games where your friend Alice tries to cheat you out of your hard-earned money by wiggling her eyebrows at her friend Bulb and sending him her hand in poker. I'm not sure this is legal because they're young but anyway. So collusion in protocols is pretty much the same thing so collusion happens when corrupt parties send some kind of disallowed information through subliminal messages for example their poker hand and so a collusion free protocol is one where if you have a local adversary that is an adversary that don't where the corrupted parties don't automatically share information then you can prove that corrupted parties can be emulated by non-colluding ideal adversaries. Okay so is it possible then to have this security guarantee for protocols that are played on the network and the somewhat surprising answer is yes so you can play poker with your friend without being cheated out of your hard-earned money online and but this yes has sort of an asterisk because this is only possible as far as we know in these two settings so the first setting is through restricted communications so with a for example a semi-trusted mediator and the second setting is in the broadcast model but we don't allow abort and also we have we need physical envelopes so okay so it seems like mediator is nice because we allow abort but why don't we use it the reason is because a potentially malicious mediator can cut off communication between it and some note some player in the game for example and this is indistinguishable from that player being malicious and just not sending any messages to the mediator so basically what we mean is that a mediator that's malicious means that there is no fairness and no identifiable abort which is bad for games okay so let's try with broadcast so in broadcast what we want ideally is we don't necessarily want like a fit assumption on physical envelopes and so we want something like a composable protocol which is means that we can have multiple games being paid at the same time and thirdly we want some guarantees in case of abort so and that third point our protocols will be proven to be inclusion free in the following model which is called rational protocol design RPD so which says that basically a protocol is inclusion free if a rational attacker won't deviate from it and what that just means is that we make it so that in our protocol it doesn't make sense for a rational attacker to deviate because it incurs a negative payoff for him and so how do we do that we replace the physical envelope with hardware tokens and the idea is basically to make the MPC protocol deterministic by having the token generate and also hide from the adversary the randomness and so what we get from this is composability and also since abort or misbehavior is publicly of a revival this behavior can be penalized for example using smart contract