 Hi everyone, so I'm excited to be here tonight to bring you the thrilling sequel to my co-authors previous work The crypto chickens cross the road This is joint work with my advisor Jonathan Katz and our lovely collaborator Julian Okay, so synchronous consensus with asynchronous fallback the crypto chickens go to the beach All right, so the chicken cryptographers club is deciding whether to take a trip to the beach and now When you or I go to the beach maybe the worst thing that can happen is that you forget your sunscreen or a seagull steals your French fries But the chickens have to be extra careful because they are always at risk of being attacked by wily foxes So either all of the chickens should go so that they have strength in numbers and they can fend off Attacks from the foxes where they should all stay home where they'll be safe So the chickens set out organizing their trip by sending emails to the end members of the club mailing list Unfortunately, they know from experience that the mailing list may have been infiltrated by up to f foxes or faults Being cryptographers they decide to use a synchronous Byzantine agreement protocol to decide whether to go to the beach because of course These protocols have the property that they ensure consistency that either all chickens decide to go or all chickens Decide to stay home as long as there are not too many foxes that have snuck their way onto the mailing list So they select a protocol that tolerates the optimal number of fox spies f less than n over 2 Assuming of course that the chickens have a properly configured pki As if the chickens task was not difficult enough they soon face another roadblock one of the email server admins is also a fox So sometimes the chickens find that their emails have been delayed or reordered while at other times everything seems to work normally So they have no way of knowing on the day that they are trying to plan this trip to the beach whether or not The emails will go through as they expect So they know that they could use an asynchronous Byzantine agreement protocol of course which would weather any unpredictable network delays However, these protocols can only tolerate up to n over 3 foxes as opposed to the optimal n over 2 tolerated by a synchronous protocol Can the chickens devise a protocol that defends against fs greater than or equal to n over 3 foxes when the network is synchronous but still withstands some f a greater than zero foxes when the network is asynchronous and Because these slides do not have my clever animations. The answer is already in front of you. Yes Our result shows that it is possible if and only if to fs plus f a it's less than n So the chickens had a lovely day at the beach and they all lived happily ever after using our protocol And I see that this has not been updated to reflect the fact that just yesterday I woke up to an email that this will be appearing at TCC So please come and learn more about our clever chickens