Abstract
Blockchain's popularity has seen a historic rise over the last decade. However, existing blockchain systems have a major issue with scalability, which has become one of the main obstacles in technology's adoption in mainstream. There have been several attempts to address this limitation by identifying Blockchain's scalability/performance bottlenecks (e.g. those mainly related to consensus algorithms), and thus proposed different solutions (e.g., new consensus protocols) to address such limitations. Other works applied sharding to tackle the issue. All solutions however have mainly focused on Cryptocurrency applications, and thus addressing the scalability of blockchain systems for general applications remains a concern. This work proposes a scalable blockchain protocol for general applications (i.e., not restricted to Cryptocurrencies). To improve the two major factors affecting transaction scalability, namely throughput and latency, we needed to modify both the blockchain structure as well as the block generation process. ZyConChain, the proposed Blockchain system, introduces three types of blocks that form three separate chains: parentBlock, sideBlock and state block. These blocks are generated based on different consensus algorithms, as each algorithm has specific properties that make it suitable for each type of block. To improve the overall performance, ZyConChain generates sideBlocks (that carry transactions) at a high rate and keep them in a pool. To generate parentBlock, miners, instead of packing transactions into a block as they do in conventional blockchains, pack sideBlocks into a parentBlock. SideBlocks are generated based on an adapted Zyzzyva consensus protocol, with O(\log n) complexity. This has reduced the final consensus complexity per transaction, in comparison to previous work. To enable the protocol to scale out with the increase in the number of nodes, ZyConChain applied sharding technique. Parallel state chains have also been introduced to address cross-shard transactions.
Highlights
Blockchain, as a promising solution to develop secure distributed ledgers, has gained an increasing attention over the last decade
The strong security features, namely integrity, immutability, and transparency that Blockchain offers, has made the technology well-suited for applications with high security requirements, and can benefit other sectors, such as Supply chain, e-voting, Internet of Things (IoT), Healthcare & medical records, and Government records
Another well-studied approach to address scalability is the sharding method [4], which partitions the nodes in a network into small groups with the aim that committees work in parallel to process transactions
Summary
Blockchain, as a promising solution to develop secure distributed ledgers, has gained an increasing attention over the last decade. When dealing with an ever increasing number of users, miners, and transactions, blockchain is unable to scale and provide the same performance as centralised systems (e.g. centralised payment systems) Without addressing this fundamental scalability problem, such a promising technology may not be able to be adopted in mainstream. Scalability remains a problem in ByzCoin and Bitcoin-NG, as they are unable to scale out when the number of miners in the network increases [17] Another well-studied approach to address scalability is the sharding method [4], which partitions the nodes in a network into small groups (called committees) with the aim that committees work in parallel to process transactions. A roadmap of the paper is provided at Figure 2
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