How can we defend Blockchains and peer-to-peer systems, when no central authority provides admission control? Resource-burning (proof-of-work, proof-of-state, CAPTCHAs) is one of the most used tools to defend such systems, but it is currently poorly understood mathematically. In this talk, I survey recent research to better understanding resource burning, in order to reduce its cost, and thereby improve system security.

Keywords: Distributed algorithms, game theory, costly signaling, money burning, Sybil attack, blockchains, cryptocurrencies, peer-to-peer.