Towards Scaling Blockchain Systems via Sharding

Abstract

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.In this work, we take a principled approach to apply sharding, which is a well-studied and proven technique to scale out databases, 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, by doing so we improve individual shards' throughput. Next, we design an efficient shard formation protocol that leverages a trusted random beacon to securely assign 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 state-of-the-art solutions at scale. More importantly, our sharded blockchain reaches a high throughput that can handle Visa-level workloads, and is the largest ever reported in a realistic environment.

When Blockchain Meets SGX: An Overview, Challenges, and Open Issues

“…Data sealing can help an enclave to swap data with another enclave or to ease memory pressure. Few schemes describe the function because it is S id e -c h a n n e l a tt a c k s S in g le -p o in t a tt a c k s AHL [69] PoUW [47] PoET [48] PoLK [49] Hybster [53] SPoS [56] Hawk [57] ShadowEth [58] Ekiden [59] FastKitten [62] TC [63] Teechain [65] Tesseract [66] BITE [67] Obscuro [68] Airtnt [70] PrivacyGuard [71] TID [72] means that the scheme uses the function or suffers from the disadvantage. means that the scheme does not use the function or suffer from the disadvantage.…”

“…However, those schemes rely on the unspent transaction output (UTXO) model and thus are only appropriate for the permissionless blockchain systems (e.g., Bitcoin). Dang et al [69] propose a sharded blockchain scheme (AHL) that extends sharding to permissioned blockchain systems and has enhanced performance. AHL implements the shard formation protocol to secure confirmation of the node-to-committee assignment.…”

ResilientDB

“…Sharding is an indispensable tool used by database systems to deal with Big Data [1,26,27,34,76,88]. Unsurprisingly, recent blockchain systems such as SharPer, Elastico, Monoxide, AHL, and RapidChain explore the use of sharding within the design of a replicated blockchain [6,7,30,67,92,95]. To further enable sharded designs, also high-performance communication primitives that enable communication between fault-tolerant clusters (shards) have been proposed [53].…”

“…The main limitation of sharding is the efficient evaluation of complex operations across shards [12,76], and sharded systems achieve high throughputs only if large portions of the workload access single shards. For example, in SharPer [7] and AHL [30], two recent permissioned blockchain designs, consensus on the cross-shard transactions is achieved either by running Pbft among the replicas of the involved shards or by starting a two-phase commit protocol after running Pbft locally within each shard, both methods with significant cross-shard costs.…”

A Cost-Effective Approach to Securing Systems through Partial Decentralization

“…As of 2020, there is no known approach to creating a scalable decentralized network which would not require all network nodes to participate in every transaction validation except sharding, which also does not allow to scan indefinitely. 4 Additionally, each decentralized network participant must obtain some profit from participating in the DDP support process, or otherwise the network will not get enough participants. 5 Most of modern decentralized data platform use cryptocurrency rewards to reward those who support the network, so that they have a strong financial incentive to participate in it.…”