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Talks & Seminars
Title: YODA: Enabling Computationally Intensive Contracts on Blockchains with Byzantine and Selfish Nodes
Prof. Vinay J. Ribeiro, IIT Delhi
Date & Time: April 3, 2019 15:30
Venue: Department of Computer Science and Engineering, Room No. 109, 01st Floor, New CSE/CC Building
Abstract:
One major shortcoming of permissionless blockchains such as Bitcoin and Ethereum is that they are unsuitable for running Computationally Intensive smart Contracts (CICs). This prevents such blockchains from running Machine Learning algorithms, Zero-Knowledge proofs, etc. which may need non-trivial computation. In this talk, we present YODA, which is to the best of our knowledge the first solution for efficient computation of CICs in permissionless blockchains with guarantees for a threat model with both Byzantine and selfish nodes. YODA selects one or more execution sets (ES) via Sortition to execute a particular CIC off-chain. One key innovation is the MultI-Round Adaptive Consensus using Likelihood Estimation (MIRACLE) algorithm based on sequential hypothesis testing. MIRACLE allows the execution sets to be small thus making YODA efficient while ensuring correct CIC execution with high probability. It adapts the number of ES sets automatically depending on the concentration of Byzantine nodes in the system and is optimal in terms of the expected number of ES sets used in certain scenarios. Through a suite of economic incentives and technical mechanisms such as the novel Randomness Inserted Contract Execution (RICE) algorithm, we force selfish nodes to behave honestly. We also prove that the honest behavior of selfish nodes is an approximate Nash Equilibrium. Our prototype implementation built on top of Ethereum demonstrates the ability of YODA to run CICs with orders of magnitude higher gas per unit time as well as total gas requirements than Ethereum currently supports.
Speaker Profile:
Vinay J. Ribeiro is currently an Associate Professor in the Department of Computer Science and Engineering at the Indian Institute of Technology Delhi. He received his B. Tech. from I. I. T. Madras in Electrical Engineering and his M. S. and Ph. D. degrees from Rice University in Electrical and Computer Engineering. His was awarded the Microsoft Outstanding Young Faculty Fellowship from IIT Delhi, a Texas Instruments Fellowship from Rice University, and was elected to Eta Kappa Nu, the IEEE honor society. He won the best student paper award at the Passive and Active Measurement (PAM) workshop 2003 for his paper on “pathchirp” which today has over a thousand citations. His research interests are in Computer and Network Security (blockchain, IoT security, intrusion detection), Wireless Networks (cognitive radio, LTE, Wi-Fi, Li-Fi), and indoor positioning and navigation.
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