March 10th, 2020 (13:15 | SR 9): CT-Talk with Dr. Krzysztof Pietrzak

on "New proof systems for sustainable blockchains: proofs of space and verifiable delay functions"


The distinctive feature of Bitcoin is that it achieves decentralisation in an open setting where everyone can join. This is achieved at a high price, honest parties must constantly dedicate more computational power towards securing Bitcoin's blockchain than is available to a potential adversary, which leads to a massive waste of energy; at its hitherto peak, the electricity used for Bitcoin mining equaled the electricity consumption of Austria. In this lecture I will discuss how disk-space, instead of computation, can be used as a resource to construct a more sustainable blockchain. We will see definitions and constructions of "proof of space" and "verifiable delay functions", and how they can be used to construct a Blockchain with similar dynamics and security properties as the Bitcoin blockchain.


Krzysztof Pietrzak received his masters and PhD from ETH Zurich, then did postdocs at ENS Paris and CWI Amsterdam. Since 2011 he heads the cryptography group at the recently founded Institute of Science and Technology Austria (IST Austria). He is interested in theoretical and applied aspects of cryptography, including pseudorandomness/entropy, (black-box) lower bounds, leakage-resilience, memory-hard functions, crypto for light-weight devices and proof systems for sustainable blockchains. He is the recipient of an ERC starting and consolidator grant and three Eurocrypt best paper awards.