Hi Cheng, This is an interesting proposal! While the incentive analysis is sound, I have two concerns:
## What if a guy keeps mining easy blocks to launch 51% attacks? With PoLW, a miner can sacrifice the coinbase reward as much as possible to mine blocks faster. If the blockchain follows the longest chain rule, PoLW may make 51% attacks much easier. An easy way of fixing this is to choose the chain with most work rather than most blocks. ## What if the coinbase tx is no longer the majority of mining reward, but the fx fee? This might happen in the future. A possible solution is to limit the number of txs for easy blocks. For example, if a miner chooses to mine blocks N times easier, he can only include txs of which the total size is <= (block_size - metadata_size) / N. Best regards, Runchao > Date: Sun, 8 Dec 2019 11:43:49 +0100 > From: Cheng Wang <ch...@alephium.org> > To: bitcoin-dev@lists.linuxfoundation.org > Subject: [bitcoin-dev] Reducing energy consumption and increasing > security at the same time > Message-ID: > <CAJgZxF4G_BjJ=ohuzhjfztkepnec2hz8dmzzfzwkbnh17xh...@mail.gmail.com> > Content-Type: text/plain; charset="utf-8" > > Hi Everyone, > > I would like to share my serious work on reducing the energy consumption of > PoW without sacrificing security. My new type of algorithm is called PoLW. > For a practical system where mining is profitable, PoLW could actually > improve the security of the system. > > The idea is to shift part of the external cost of mining in the physical > world (mainly energy consumption) to the internal cost of the network. In > PoLW, the miners are able to give up part of the coinbase reward so as to > get weight (> 1) for the block hash they produce. The total cost of > generating a new block would still be equal to maximal coinbase reward in > equilibrium. > > I analyzed two algorithms in the paper: linear PoLW and exponential PoLW. > Linear PoLW could reduce energy consumption by a factor close to 1/2 in > equilibrium, while exponential PoLW could reduce energy consumption by an > arbitrary factor in equilibrium. > > In a practical system, mining is usually (if not always) profitable. If we > transition from PoW to PoLW, the external costs of mining would decrease > and the internal costs will increase. However, the decrease in external > costs would be less than the increase in internal costs since mining is > profitable. The total cost of block generation would get higher, therefore, > the security will increase. > > Of course, we could not decrease the external costs of any existing system > by a factor close to zero immediately. There is a section in my paper > discussing this particularly. The principle of applying PoLW is that > keeping the absolute external cost increasing all the time, but the > percentage of external cost in the total cost gets lower eventually. > > This work is based on solid math calculation, and I am looking forward to > feedback and discussions. My paper is available at: > https://github.com/alephium/research/raw/master/polw.pdf > > It's inspired by the recent great paper of Itay, Alexander, and Ittay: > https://arxiv.org/abs/1911.04124 > > Best, > Cheng Wang
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