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R. Kuznets:
"Causality in the Age of Fake News";
Talk: Seminar "Logic and Theoretical Computer Science", University of Bern (2019), Bern (invited); 2019-10-31.

As recently formulated by Yoram Moses, actions are not based on facts but rather on our knowledge of facts. This Knowledge of Preconditions Principle (KoP) underscores the central role that knowledge plays in decision making. The propagation of information in asynchronous in asynchronous distributed systems, i.e., those where agents do not have access to a global synchronized clock, has been well studied. It can rely solely on chains of messages, which form what Leslie Lamport called a causal cone. Until recently, this causality analysis existed only for fault-free systems and systems with very restricted types of faults. In our talk, we generalize the concept of the causal cone to systems with arbitrary byzantine failures and extract necessary conditions for achievable states of knowledge in fault-tolerant distributed systems.