While showing great promise, Bitcoin requires users to wait tens of minutes transactions to commit, and even then, offering only probabilistic. This paper introduces ByzCoin, a novel Byzantine consensus protocol leverages scalable collective signing to commit Bitcoin transactions within seconds. ByzCoin achieves Byzantine consensus while Bitcoin's open membership by dynamically forming hash-proportionate consensus groups that represent recently-successful block. ByzCoin employs communication trees to optimize transaction commitment verification under normal operation while guaranteeing safety and liveness Byzantine faults, up to a near-optimal tolerance of f faulty group among 3f + 2 total. ByzCoin mitigates double spending and selfish attacks by producing collectively signed transaction blocks within one of transaction submission. Tree-structured communication further reduces latency to less than 30 seconds. Due to these optimizations, ByzCoin a throughput higher than PayPal currently handles, with a confirmation of 15-20 seconds.
Kokoris-Kogias et al. (2016) studied this question.