HashCore: Proof-of-Work Functions for General Purpose Processors (1902.00112v2)

Abstract: Over the past five years, the rewards associated with mining Proof-of-Work blockchains have increased substantially. As a result, miners are heavily incentivized to design and utilize Application Specific Integrated Circuits (ASICs) that can compute hashes far more efficiently than existing general purpose hardware. Currently, it is difficult for most users to purchase and operate ASICs due to pricing and availability constraints, resulting in a relatively small number of miners with respect to total user base for most popular cryptocurrencies. In this work, we aim to invert the problem of ASIC development by constructing a Proof-of-Work function for which an existing general purpose processor (GPP, such as an x86 IC) is already an optimized ASIC. In doing so, we will ensure that any would-be miner either already owns an ASIC for the Proof-of-Work system they wish to participate in or can attain one at a competitive price with relative ease. In order to achieve this, we present HashCore, a Proof-of-Work function composed of "widgets" generated pseudo-randomly at runtime that each execute a sequence of general purpose processor instructions designed to stress the computational resources of such a GPP. The widgets will be modeled after workloads that GPPs have been optimized for, for example, the SPEC CPU 2017 benchmark suite for x86 ICs, in a technique we refer to as inverted benchmarking. We provide a proof that HashCore is collision-resistant regardless of how the widgets are implemented. We observe that GPP designers/developers essentially create an ASIC for benchmarks such as SPEC CPU 2017. By modeling HashCore after such benchmarks, we create a Proof-of-Work function that can be run most efficiently on a GPP, resulting in a more accessible, competitive, and balanced mining market.

• The paper introduces HashCore, a Proof-of-Work function using runtime-generated widgets that mimic benchmark workloads to optimize mining for general-purpose processors.
• HashCore is designed with a collision-resistance property, proven assuming base hash function security, and validated experimentally on GPPs showing feasible execution metrics.
• This approach offers potential benefits like democratizing blockchain mining by lowering the hardware barrier, improving economic efficiency, and addressing sustainability concerns associated with ASICs.

Assessing "HashCore: Proof-of-Work Functions for General Purpose Processors"

The paper "HashCore: Proof-of-Work Functions for General Purpose Processors" by Yanni Georghiades et al. presents a novel approach within blockchain systems, emphasizing the development of a Proof-of-Work (PoW) function optimized for pre-existing general-purpose processors (GPPs) rather than custom Application Specific Integrated Circuits (ASICs). This method proposes a shift from the traditional emphasis on hardware specialization towards leveraging ubiquitous computational resources.

Core Contributions

The authors introduce HashCore, a PoW function that utilizes "widgets," which are pseudo-randomly generated at runtime. These widgets execute sequences of GPP instructions, similar to workload profiles for which GPPs are inherently optimized. The distinctive aspect of this work is the adoption of what is termed "inverted benchmarking", where the widgets mimic benchmark workloads like those found in SPEC CPU 2017. The primary assertion is that general-purpose processors, widely available, become the natural ASIC for this mining approach, democratizing access to mining capabilities.

Technical Examination and Results

The paper provides a collision-resistance proof for HashCore, a critical property ensuring blockchain integrity. Assuming the base hash functions like SHA-256 are collision-resistant, the authors offer a reduction-based proof that this property is maintained. The experimental validation was performed on a Dell PowerEdge R320 server, using SPEC CPU benchmarks, providing quantitative insights into performance profiles. Here, the processors exhibit similar execution metrics compared to typical computational loads, validating the feasibility of HashCore from a computational efficiency standpoint.

Implications and Future Directions

This research invokes several important implications for blockchain mining:

1. Democratized Mining: The approach would ostensibly lower the financial barrier of entry into mining by allowing existing general computational hardware to mine effectively. This broadens participation across individuals possessing consumer-grade GPPs, fostering a more decentralized network structure.
2. Economic Efficiency: The feasibility of mining on non-specialized hardware could introduce efficiency into the blockchain ecosystem, as GPPs can be repurposed when not mining, reducing financial risk.
3. Sustainability Considerations: By capitalizing on general-purpose computational capabilities, the model could reduce wastefulness attributed to mining-specific ASICs that lack alternative utility.
4. Platform Versatility: While the paper focuses on x86 architectures, the mechanism could potentially adapt to ARM or other architectures, showcasing HashCore’s adaptability.

Future Work

The paper suggests several avenues for further exploration. Ensuring provable optimality of HashCore within various architectures remains an open challenge. Additionally, the exploration of integrating socially beneficial computational tasks (e.g., scientific computations) into PoW mining, without compromising security, could enhance blockchain's societal value. Moreover, deeper assessments of economic dynamics in mining with HashCore and possibilities for preventing centralized control due to energy or hardware monopolies are crucial for practical deployments.

In conclusion, Georghiades et al. present a compelling case for re-evaluating PoW strategies. By targeting existing GPPs, they propose a potentially transformative approach within the cryptocurrency mining landscape to encourage greater inclusivity and equitable resource deployment. While alternative PoW strategies have surfaced, HashCore’s modular and adaptable framework positions it uniquely in facilitating blockchain's sustained viability and growth.