Subject: [bitcoin-dev] Bitcoin Days Destroyed as block selection heuristic

From: Dave Scotese <[email-masked]>
Date: Fri, 11 Sep 2015 09:27:25 -0700

Rather than (promising to, and when they don't actually, at least
pretending to) use the first-seen block, I propose that a more
sophisticated method of choosing which of two block solutions to accept.
Essentially, a miner receiving two solutions at the same height would
compute a weighted sum of bitcoin-days-destroyed (transactions received
earlier get higher weights) of whatever transactions are in a block *and
also* were in the miner's mempool *before* the first solution arrived.
Whichever block has more wins.

This strategy avoids allowing miners to use private transactions to mess
with the blockchain.  It also makes an empty block far less attractive
because it is easily replaced, all the way until the next block locks it
in.  Any block-selection heuristic can be gamed, but I believe that using a
weighted sum of BTCDD is harder to game than using block propagation timing.

I asked Can Bitcoin Days Destroyed be a better resolution mechanism for
competing blocks?
<http://bitcoin.stackexchange.com/questions/39226/can-bitcoin-days-destroyed-be-a-better-resolution-mechanism-for-competing-blocks>
on the stackexchange bitcoin site in order to collect objections to and
problems with this idea, and have not found any that I haven't addressed.
The best objection is that *maybe* empty blocks and selfish mining are
either good for bitcoin, or else they are so minimally bad that no effort
ought to be expended in preventing them.

If anyone here thinks this is a good idea, and no one can offer reasons
it's a bad idea, I will probably start working on an implementation.  I'm
really slow though, so ping me if it looks like fun to you.

notplato