The recent interest in blockchains has led to a thorough investigation of their security in the research community. Traditionally, blockchain protocols have been shown to be secure under the assumption that end-to-end network delays are bounded. In this talk, I will discuss some recent research that relaxes this assumption. In particular, I will discuss the security of the longest-chain protocol, used in Bitcoin and other cryptocurrencies, in a network with random, possibly unbounded delays. The analysis of this problem boils down to relatively simple properties of random processes. I will conclude the talk with a broader discussion of the robustness of blockchains under network delay. Based on:  The longest chain protocol under random delays. With Bruce Hajek. Accepted for publication in Stochastic Systems, 2023.  Blockchain CAP theorem allows user-dependent adaptivity and finality. With Xuechao Wang, Sreeram Kannan and Pramod Viswanath. Published in Financial Cryptography, 2021.
Dr. Suryanarayana Sankagiri, EPFL, Switzerland
Suryanarayana Sankagiri (Surya) is a postdoctoral researcher in the Information and Network Dynamics Lab at EPFL, Switzerland. He received his M.S. and Ph.D. from the University of Illinois at Urbana-Champaign (UIUC) in 2022 and his B.Tech. from IIT Bombay in 2016. Surya is most passionate about studying real-world systems through mathematical modelling and analysis using tools from probability, networks, and optimization. His Ph.D. research covered various facets of blockchain security and efficiency. His current research interest is in designing systems that learn from comparisons and choices, with a particular focus on interactive search and recommendation systems.