Deconstructing the Blockchain to Approach Physical Limits (1810.08092v4)

Abstract: Transaction throughput, confirmation latency and confirmation reliability are fundamental performance measures of any blockchain system in addition to its security. In a decentralized setting, these measures are limited by two underlying physical network attributes: communication capacity and speed-of-light propagation delay. Existing systems operate far away from these physical limits. In this work we introduce Prism, a new proof-of-work blockchain protocol, which can achieve 1) security against up to 50% adversarial hashing power; 2) optimal throughput up to the capacity C of the network; 3) confirmation latency for honest transactions proportional to the propagation delay D, with confirmation error probability exponentially small in CD ; 4) eventual total ordering of all transactions. Our approach to the design of this protocol is based on deconstructing the blockchain into its basic functionalities and systematically scaling up these functionalities to approach their physical limits.

• The paper introduces a deconstructed blockchain architecture by separating proposer, voter, and transaction blocks to facilitate independent scaling.
• The paper achieves near-optimal throughput by utilizing up to 90% of network capacity, operating at approximately 0.9(1-β)C for transactions.
• The paper ensures robust security by leveraging parallel voter chains and Bitcoin-inspired properties to protect against adversaries with up to 50% hashing power.

An Expert Essay on "Prism: Deconstructing the Blockchain to Approach Physical Limits"

The paper "Prism: Deconstructing the Blockchain to Approach Physical Limits" introduces a novel proof-of-work (PoW) blockchain protocol aimed at optimizing various performance measures such as transaction throughput and confirmation latency, within the bounds imposed by physical network characteristics. The protocol, named Prism, employs a deconstructed approach to traditional blockchain architecture, aiming to achieve near-optimal throughput, fast confirmation times, and robust security.

Key Contributions

Prism offers several novel concepts and structured mechanisms to enhance blockchain performance:

1. Deconstruction of Functionalities: The protocol decouples the core functionalities of blockchains into separate components, particularly emphasizing proposer blocks, voter blocks, and transaction blocks. This separation facilitates independent scaling, allowing the system to address throughput and latency issues without compromising security.
2. Near-Optimal Throughput: The protocol is designed to utilize up to 90% of the network capacity for throughput, theoretically allowing transactions to happen at the rate of 0.9(1-β)C, where C is the network capacity and β is the fraction of adversarial hash power tolerated. Such throughput is very close to the theoretical maximum, considering each transaction needs to be communicated at least once.
3. Fast Confirmation and Security: Prism achieves secure transaction confirmation with a latency primarily dictated by the speed-of-light propagation delay across the network, D, provided the confirmation error probability does not approach implausibly small values. The design leverages multiple voter blocks operating in parallel, a concept inspired by techniques similar to list decoding in information theory, which allows the system to quickly narrow down potential block leaders among levels in the proposer tree.
4. Robust Security Framework: Prism ensures security against adversaries controlling up to 50% of the total hashing power, leveraging the common-prefix, chain growth, and chain quality properties adapted from the Bitcoin backbone protocol to secure the voter chains.

Implications and Future Directions

The implications of this research are both practical and theoretical. Prism proposes a sophisticated method to balance security with enhanced performance in terms of throughput and latency. The introduction of multi-dimensional blocktree architecture may inspire further research on scalability solutions perhaps beyond PoW systems, including proof-of-stake (PoS) and Byzantine Fault Tolerance (BFT) hybrid models.

Theoretically, the structured approach offers a fresh perspective on blockchain architecture, highlighting the potential of decoupling various components to solve computational and network limitations effectively. As the protocol matures, it may lead to additional theoretical insights into the limits of communication versus computation, especially when applied to distributed ledger technologies.

Speculation on AI and Blockchain Synergy

While the paper focuses on blockchain parameters, future developments could also see AI and machine learning assisting effective communication between nodes to better manage confirmations, thus optimizing latency further. AI could help in analyzing network behavior patterns to adaptively adjust parameters for optimal performance.

In conclusion, Prism makes significant strides towards redefining blockchain capabilities by dismantling and reimagining core blockchain functionalities, achieving scalability and speed while maintaining robust security postures. It paves the way for future blockchain designs that aspire to meet the ultimate physical limits of network infrastructures.