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1. Dynamic power control for rational cryptocurrency mining

   https://doi.org/10.1145/3410699.3413797  

   Chang, Sang-Yoon; Wuthier, Simeon (September 2020, the 3rd Workshop on Cryptocurrencies and Blockchains for Distributed Systems)

   In blockchain and cryptocurrency, miners participate in a proof-of-work-based distributed consensus protocol to find and generate a valid block, process transactions, and earn the corresponding reward. Because cryptocurrency is designed to adapt to the dynamic miner network size, a miner's participation affects the block difficulty which sets the expected amount of work to find a valid block. We study the dependency between the mining power control and the block difficulty and study a rational miner utilizing such dependency to dynamically control its mining power over a longer horizon than just the impending block. More specifically, we introduce I-O Mining strategy where a miner takes advantage of the block difficulty adjustment rule and toggles between mining with full power and power off between the difficulty adjustments. In I-O Mining, the miner influences the block difficulty and mines only when the difficulty is low, gaming and violating the design integrity of the mining protocol for its profit gain. We analyze the I-O Mining's incentive/profit gain over the static-mining strategies and its negative impact on the rest of the blockchain mining network in the block/transaction scalability. Our results show that I-O Mining becomes even more effective and profitable as there are greater competitions for mining and the reward and the cost difference becomes smaller, which are the trends in cryptocurrencies. 

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2. Blockumulus: A Scalable Framework for Smart Contracts on the Cloud

   https://doi.org/10.1109/ICDCS51616.2021.00064  

   Ivanov, Nikolay; Yan, Qiben; Wang, Qingyang (July 2021, 2021 IEEE 41st International Conference on Distributed Computing Systems (ICDCS))

   Public blockchains have spurred the growing popularity of decentralized transactions and smart contracts, especially on the financial market. However, public blockchains exhibit their limitations on the transaction throughput, storage availability, and compute capacity. To avoid transaction gridlock, public blockchains impose large fees and per-block resource limits, making it difficult to accommodate the ever-growing high transaction demand. Previous research endeavors to improve the scalability and performance of blockchain through various technologies, such as side-chaining, sharding, secured off-chain computation, communication network optimizations, and efficient consensus protocols. However, these approaches have not attained a widespread adoption due to their inability in delivering a cloud-like performance, in terms of the scalability in transaction throughput, storage, and compute capacity. In this work, we determine that the major obstacle to public blockchain scalability is their underlying unstructured P2P networks. We further show that a centralized network can support the deployment of decentralized smart contracts. We propose a novel approach for achieving scalable decentralization: instead of trying to make blockchain scalable, we deliver decentralization to already scalable cloud by using an Ethereum smart contract. We introduce Blockumulus, a framework that can deploy decentralized cloud smart contract environments using a novel technique called overlay consensus. Through experiments, we demonstrate that Blockumulus is scalable in all three dimensions: computation, data storage, and transaction throughput. Besides eliminating the current code execution and storage restrictions, Blockumulus delivers a transaction latency between 2 and 5 seconds under normal load. Moreover, the stress test of our prototype reveals the ability to execute 20,000 simultaneous transactions under 26 seconds, which is on par with the average throughput of worldwide credit card transactions. 

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3. On Sharding Permissioned Blockchains.

   Mohammad Javad Amiri, Divyakant Agrawal (July 2019, IEEE International Conference on Blockchain)

   Permissioned Blockchain systems rely mainly on Byzantine fault-tolerant protocols to establish consensus on the order of transactions. While Byzantine fault-tolerant protocols mostly guarantee consistency (safety) in an asynchronous network using 3f+1 machines to overcome the simultaneous malicious failure of any f nodes, in many systems, e.g., blockchain systems, the number of available nodes (resources) is much more than 3f + 1. To utilize such extra resources, in this paper we introduce a model that leverages transaction parallelism by partitioning the nodes into clusters (partitions) and processing independent transactions on different partitions simultaneously. The model also shards the blockchain ledger, assigns different shards of the blockchain ledger to different clusters, and includes both intra-shard and cross-shard transactions. Since more than one cluster is involved in each cross-shard transaction, the ledger is formed as a directed acyclic graph. 

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4. MoneyMorph : Censorship Resistant Rendezvous using Permissionless Cryptocurrencies

   https://doi.org/10.2478/popets-2020-0058  

   Minaei, Mohsen; Moreno-Sanchez, Pedro; Kate, Aniket (July 2020, Proceedings on Privacy Enhancing Technologies)

   null (Ed.)

   Abstract Cryptocurrencies play a major role in the global financial ecosystem. Their presence across different geopolitical corridors, including in repressive regimes, has been one of their striking features. In this work, we leverage this feature for bootstrapping Censorship Resistant communication. We conceptualize the notion of stego-bootstrapping scheme and its security in terms of rareness and security against chosencovertext attacks. We present MoneyMorph , a provably secure stego-bootstrapping scheme using cryptocurrencies. MoneyMorph allows a censored user to interact with a decoder entity outside the censored region, through blockchain transactions as rendezvous, to obtain bootstrapping information such as a censorshipresistant proxy and its public key. Unlike the usual bootstrapping approaches (e.g., emailing) with heuristic security, if any, MoneyMorph employs public-key steganography over blockchain transactions to ensure provable cryptographic security. We design rendezvous over Bitcoin, Zcash, Monero, and Ethereum, and analyze their effectiveness in terms of available bandwidth and transaction cost. With its highly cryptographic structure, we show that Zcash provides 1148 byte bandwidth per transaction costing less than 0.01 USD as fee. 

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5. Proof of X: Experimental Insights on Blockchain Consensus Algorithms in Energy Markets

   https://doi.org/10.1109/ISGT49243.2021.9372194  

   Machacek, Travis; Biswal, Milan; Misra, Satyajayant (February 2021, 2021 IEEE Power & Energy Society Innovative Smart Grid Technologies Conference (ISGT))

   null (Ed.)

   The current centralized model of the electricity market is not efficient in performing distributed energy transactions required for the transactive smart grid. One of the prominent solutions to this issue is to integrate blockchain technologies, which promise transparent, tamper-proof, and secure transaction systems specifically suitable for the decentralized and distributed energy markets. Blockchain has already been shown to successfully operate in a microgrid peer-to-peer (P2P) energy market. The prime determinant of different blockchain implementations is the consensus algorithm they use to reach consensus on which blocks/transactions to accept as valid in a distributed environment. Although different blockchain implementations have been proposed independently for P2P energy market in the microgrid, quantitative experimental analyses and comparison of the consensus algorithms that the different blockchains may use for energy markets, has not been studied. Identifying the right consensus algorithm to use is essential for scalability and operation of the energy market. To this end, we evaluate three popular consensus algorithms: (i) proof of work (PoW), (ii) proof of authority (PoA), and (iii) Istanbul Byzantine fault tolerance (IBFT), running them on a network of nodes set up using a network of docker nodes to form a microgrid energy market. Using a series of double auctions, we assess each algorithm's viability using different metrics, such as time to reach consensus and scalability. The results indicate that PoA is the most efficient and scalable consensus algorithm to hold double auctions in the smart grid. We also identified the minimum hardware specification necessary for devices such as smart meters, which may run these consensus algorithms 

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