Blockchain moderated by empty blocks to reduce the energetic impact of cryptomoneys Abstract   While cryptocurrencies and blockchain applications continue to gain popularity, their energy cost is evidently becoming unsustainable. In most instances, the main cost comes from the required amount of energy for the ProofofWork, and this cost is inherent to the design. In addition, useless costs from discarded work (e.g., the socalled Forks) and lack of scalability (in number of users and in rapid transactions) limit their practical effectiveness. In this paper, we present an innovative scheme which eliminates the nonce and thus the burden of the ProofofWork which is the main cause of the energy waste in cryptocurrencies such as Bitcoin. We prove that our scheme guarantees a tunable and bounded average number of simultaneous mining whatever the size of the population in competition, thus by making the use of noncebased techniques unnecessary, achieves scalability without the cost of consuming a large volume of energy. The technique used in the proof of our scheme is based on the analogy of the analysis of a green leader election. The additional difference with ProofofWork schemes (beyond the suppression of the nonce field that is triggering most of the waste), is the introduction of (what we denote as) xe2x80x9cempty blocksxe2x80x9d which aim are to call regular blocks following a staircase set of values. Our scheme reduces the risk of Forks and provides tunable scalability for the number of users and the speed of block generation. We also prove using game theoretical analysis that our scheme is resilient to unfair competitive investments (e.g., xe2x80x9d51 percentxe2x80x9d attack) and block nursing.

Pooled Mining is Driving Blockchains Toward Centralized Systems The decentralization property of blockchains stems from the fact that each miner accepts or refuses transactions and blocks based on its own verification results. However, pooled mining causes blockchains to evolve into centralized systems because pool participants delegate their decisionmaking rights to pool managers. In this paper, we established and validated a model for ProofofWork mining, introduced the concept of equivalent blocks, and quantitatively derived that pooling effectively lowers the income variance of miners. We also analyzed Bitcoin and Ethereum data to prove that pooled mining has become prevalent in the real world. The percentage of poolmined blocks increased from 49.91% to 91.12% within four months in Bitcoin and from 76.9% to 92.2% within five months in Ethereum. In July 2018, Bitcoin and Ethereum mining were dominated by only six and five pools respectively.