COMPARISON OF BLOCK EXPECTATION TIME FOR VARIOUS CONSENSUS ALGORITHMS
Dmytro Kaidalov, Lyudmila Kovalchuk, Andrii Nastenko, Mariia Rodinko, Oleksiy Shevtsov, Roman Oliynykov · Radio Electronics Computer Science Control · 2019
Context. We consider security properties of decentralized blockchain-based consensus protocols. The object of research is blockconfirmation time for users to get assurance that their transaction will not be reverted.Objective. The goal of the paper is to analyze double-spend attacks on the different blockchain-based systems and compareresulting probabilities of attacker’s success.Method. We presented two models for two types of attacks on the Ouroboros protocol (for the general and covert adversaries).The models allow calculating the exact number of slots needed to achieve the required level of security. It was shown that theOuroboros protocol allows achieving the required security level with significantly shorter confirmation period in comparison withBitcoin. We estimated minimal number of confirmation blocks and compare estimation time for Bitcoin, GHOST and Ouroborosprotocols. As a measure of comparison, we considered transaction confirmation time for which the probability of a double-spendattack is less than 0.1%. We use different standard probability distribution and different properties of Markov chains and RandomWalks to get comparison of estimated security properties of Bitcoin blockchain against three different models of Bitcoin doublespend attack. The splitting attack based on the model where resources of honest participants are divided to compete different chainsis applied to Bitcoin and GHOST consensus protocols. Properties of Markov chains and Random Walks are also applied to obtainsecurity estimations for the Ouroboros protocol.Results. We developed methods to get specific numbers for average block confirmation time for Ouroboros protocol. Wecompared minimal number of confirmation blocks needed to ensure a high security for considered protocols: Bitcoin, GHOST andOuroboros.Conclusions. The obtained results allow determination of security bounds for the Bitcoin, GHOST and Ouroboros consensusprotocols. Users of the practically deployed blockchain systems may get specific parameters for a given assurance level.