Subject: [bitcoin-dev] Proposal: rewarding fees to next block miner

From: Nathan Parker <[email-masked]>
Date: Sat, 27 Jan 2018 09:45:10 +0100

Miners can fill their blocks with transactions paying very high fees at no
cost because they get the fees back to themselves. They can do this for
different purposes, like trying to increase the recommended fee. Here I
propose a backwards-compatible solution to this problem.

The solution would be to reward the fees of the current block to the miner
of the next block (or X blocks after the current one). That way, if a miner
floods its own block with very high fee transactions, those fees are no
longer given back to itself, but to the miner of future blocks which could
potentially be anyone. Flooding blocks with fake txs is now discouraged.
However, filling blocks with real transactions paying real fees is still
encouraged because you could be the one to mine the block that would claim
this reward.

The way to implement this in a backwards-compatible fashion would be to
enforce miners to set an anyone-can-spend output in the coinbase
transaction of the block (by adding this as a rule for verifying new
blocks). The miner of 100 blocks after the current one can add a secondary
transaction spending this block's anyone-can-spend coinbase transaction
(due to the coinbase needing 100 blocks to mature) and thus claiming the
funds. This way, the block reward of a block X is always transferred to the
miner of block X+100.

Implementing this would require a soft-fork. Since that secondary
transaction needs no signature whatsoever, the overhead caused by that
extra transaction is negligible.

Possible Downside: When the fork is activated, the miners won’t get any
reward for mining blocks for a period of 100 blocks. They could choose to
power off the mining equipment for maintenance or to save power over that
period, so the hashrate could drop temporarily. However, if the hashrate
drops too much, blocks would take much longer to mine, and miners wouldn’t
want that either since they want to go through those 100 reward-less blocks
as soon as possible so they can start getting rewards from mining again.