Scalable and Efficient Distributed Ledgers

Thu 25Oct2018

Kokoris Kogias Eleftherios, EPFL

From 12.00 until 13.30

At CNB/F/110 (Lunch) + CAB/F/100.9 (Seminar), ETH Zurich

Universitätstrasse 6, 8092 Zurich


While showing great promise, Bitcoin requires users to wait tens of minutes for transactions to commit, and even then, offering only probabilistic guarantees. In this talk we are going to address the challenges of scaling decentralised payment systems. The first part of the talk introduces ByzCoin, a novel Byzantine consensus protocol that leverages scalable collective signing to commit Bitcoin transactions irreversibly within seconds. ByzCoin achieves Byzantine consensus while preserving Bitcoin’s open membership by dynamically forming hash power-proportionate consensus groups that represent recently-successful block miners and achieves a throughput higher than Paypal currently handles, with a confirmation latency of 15-20 seconds. ByzCoin however has limited scalability and fixed processing capacity.  The second part of the talk introduces OmniLedger, a novel scale-out distributed ledger that preserves longterm security under permissionless operation. It ensures security and correctness by using a bias-resistant public-randomness protocol for choosing large, statistically representative shards that process transactions, and by introducing an efficient crossshard commit protocol that atomically handles transactions affecting multiple shards. OmniLedger’s throughput scales linearly in the number of active validators, supporting Visa-level workloads and beyond, while confirming typical transactions in under two seconds.

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