SEMINAR:Optimal Security in a Multi-chain World

Guest: Ertem Nusret Taş, Stanford University

Title: Optimal Security in a Multi-chain World

Date/Time: April 4, 2024, 13:40 - 14:30

Location: FENS L061

Abstract: Fifteen years after the invention of Bitcoin, there has been a proliferation of many permissionless blockchains. Each such chain provides a public ledger that can be written to and read from by anyone. In this multi-chain world, a natural question arises: what is the optimal security an existing blockchain, a consumer chain, can extract by only reading and writing to k other existing blockchains, the provider chains? In this talk, we will answer this question in three ways: (1) We will first see a protocol, Babylon, where an off-the-shelf proof-of-stake protocol (acting as a consumer chain) checkpoints onto Bitcoin (the provider chain) to reduce its stake withdrawal delay and to resolve issues such as non-slashable long-range safety attacks, low liveness resilience and difficulty to bootstrap from low token valuation. (2) Applying the checkpointing method iteratively, we will then design a protocol called interchain timestamping, which enables a consumer chain to extract the maximum economic security from the provider chains, as quantified by the slashable safety resilience. (3) Finally, drawing an analogy with switching circuits, we will design two basic compositional operations between blockchains, serial and triangular compositions, and use these operations as building blocks to construct general overlay blockchains that read from and write to a given set of blockchains. This talk is based on the following papers:

·        Bitcoin-Enhanced Proof-of-Stake Security: Possibilities and Impossibilities

·        Interchain Timestamping for Mesh Security

·        A Circuit Approach to Constructing Blockchains on Blockchains

Bio: Ertem Nusret Taş is a PhD student in Electrical Engineering at Stanford University working with Prof. David Tse. He completed both his BS and MEng degrees in Electrical Engineering and Computer Science at MIT. He worked with Prof. Eytan Modiano on coflow scheduling in data center networks during his time as an MEng student. His current research interests include blockchains, consensus protocols and cryptography.