Ari: a P2P optimization for blockchain systems Distributed ledgers based on blockchain, such as Bitcoin and Ethereum, are known and used worldwide now. But the existing distributed ledgers are too slow for commercial requirements when compared with centralized systems like Visa. To tackle this issue, many strategies have been put forward, including GHOST, BitcoinNG, Sharding, State channel, Plasma, etc. But few of them is focused on the P2P layer, while the P2P layer plays a crucial role as a distributed ledger needs to be updated via block propagation process. We propose an alternative protocol named Ari, which is a P2P optimization for blockchain systems. Ari protocol makes the block propagation graph an intercrossing net rather than a unidirectional tree, thus leading to a great reduction on latency as well as a great expansion on throughput, and the security as well as scalability is still guaranteed.

Towards Scaling Blockchain Systems via Sharding Existing blockchain systems scale poorly because of their distributed consensus protocols. Current attempts at improving blockchain scalability are limited to cryptocurrency. Scaling blockchain systems under general workloads (i.e., noncryptocurrency applications) remains an open question. This work takes a principled approach to apply sharding to blockchain systems in order to improve their transaction throughput at scale. This is challenging, however, due to the fundamental difference in failure models between databases and blockchain. To achieve our goal, we first enhance the performance of Byzantine consensus protocols, improving individual shardsu0027 throughput. Next, we design an efficient shard formation protocol that securely assigns nodes into shards. We rely on trusted hardware, namely Intel SGX, to achieve high performance for both consensus and shard formation protocol. Third, we design a general distributed transaction protocol that ensures safety and liveness even when transaction coordinators are malicious. Finally, we conduct an extensive evaluation of our design both on a local cluster and on Google Cloud Platform. The results show that our consensus and shard formation protocols outperform stateoftheart solutions at scale. More importantly, our sharded blockchain reaches a high throughput that can handle Visalevel workloads, and is the largest ever reported in a realistic environment.