Abstract
Ethereum accelerates the transaction process through a quicker block creation design. Since the time interval between the generation of blocks is very short (about 15s), block propagation time in an inefficient network is not negligible compared with the block time interval. This lead to the production of a large number of orphan blocks. In order to solve the security problems that may be caused by the orphan block and improve the transaction processing efficiency, Ethereum introduces the uncle block mechanism, i.e., an orphan block may get part of minted reward if it gets a reference by a regular block. In this paper, we show the weakness of the uncle block mechanism. Firstly, we describe the specific differences of Ethereum selfish and stubborn mining in every state from the ones in Bitcoin. Secondly, we simulate possible attacks, and the results show that the Ethereum selfish and stubborn mining strategies not only increase the reward of an attacker but also decrease the security threshold. The security threshold refers to the proportion of the attacker's computational power that needs to be achieved in order to obtain a higher reward than he should. In a practical network congestion rate, the security threshold are weakened to 0.129 and 0.216 against the Lead stubborn mining strategy and the original selfish mining strategy, respectively. When the congestion rate is rising, the reward is increasing and the threshold is decreasing. Thirdly, possible strategies are evaluated to find out the optimal one in different settings. Fourthly, we also extend the evaluation by combining three eclipse attack strategies with selfish or stubborn mining. Most of combinations bring more advantages to an attacker than a single strategy.
Highlights
The innovation of Bitcoin reveals a new milestone era for E-cash [1], and decentralized cryptocurrencies have made a significant impact on financial systems
We describe the specific differences of Ethereum selfish and stubborn mining in every state from the ones in Bitcoin
We show that the uncle block mechanism decreases the security threshold against selfish and stubborn mining in a practical Ethereum network
Summary
The innovation of Bitcoin reveals a new milestone era for E-cash [1], and decentralized cryptocurrencies have made a significant impact on financial systems. Blockchain technology is being used more and more in various fields [2]. A. ETHEREUM BLOCKCHAIN Ethereum is the second generation cryptocurrency supporting smart contract coded by a Turing-complete language. Ethereum refines its proof-of-work based ancestor, Bitcoin, in several ways. Taking the structure of Ethereum block-chain as an example, The associate editor coordinating the review of this manuscript and approving it for publication was Malik Najmus Saqib
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