Post
Topic
Board Bitcoin Discussion
Re: Bitcoin 20MB Fork
by
DeathAndTaxes
on 13/02/2015, 17:55:23 UTC
Cryddit's scenario also only considers a neutral scenario where the two networks go their separate ways.  Users who have coins prior to the fork have the same coins on both sides of the fork as well.  If one believes that the minority fork will die and thus the coins on that fork have no value they could be used to pay txn fees to buy up all the block space and help that inevitability occur much quicker.

Pre-fork coins however are valid on both networks which would mean making worthless transactions would result in losing coins on both forks due to fees.  One would obviously want to ensure these high fee transactions are valid only on the minority network.  The first thing would be to get a single output which is only valid on one chain.  Either the majority or the minority works so lets just look at the minority network.  The newly mined coins after the fork are only valid that chain.  For example at say block height 400,000 there will be two blocks 400,000a and 400,000b.  The coins from the coinbase reward in 400,000a can't be spent on the b network because they don't exist.  Even a single satoshi of post-fork coins can be used to turn pre-fork coins into post-fork coins.  A transaction which has as its inputs any number of pre-fork inputs plus at least one post fork input will create outputs which are spendable only on one of the forks.

100 BTC of prefork coins + 1 satoshi of post fork minority coinbase coins = 100.00000001 BTC worth of minority only coins.

Since this transaction can't exist on the majority network any txns which occur 'downstream' from it also can't exist on the majority network.  You could now spend this 100 BTC in fees on the minority network and still have the 100 BTC on the majority network.

Cryddit assumes after the fork occurs some miners will abandon it but lets be generous and assume that the full 5% continue to use the original network (if more than 5% do not support the fork it won't happen).  Lets also be generous and assume all build nothing but 1MB blocks (something miners today don't even do).  That would be only 7.2MB per day in block space.  To create paying txns which use up the entire block would only be 0.72 BTC per day in fees.  So just keep creating txns sending coins back to yourself paying a fee and use ensure all blocks are full.  Legitimate users however can pay higher than the minimum fee so it is just a question of how high you want to push the fees.   If you make txns with 10x the normal fee then everyone else will need to pay more than 10x the normal fee to get confirmations and that would only cost 7.2 BTC per day in fees.  

In the "1MB is a great idea" post I pointed out that if txn demand exceeds block capacity by some significant margin it will occur off-chain on centralized systems and those centralized systems will eventually consume all the block space for settlement transactions.  Since they can outpay direct users in txns fees they will squeeze out the direct users.  The high fee txns is a good way to illustrate that at no cost on the minority fork.  I think someone in this thread said Bitcoin would be great even if it cost $5 per transaction.  If the average txn is 500 bytes then $5 per txn would be $10,000 per MB or 288 BTC spent in fees per day.  That might be much for a single user to do but a group of users working together could do it.  No legitimate txn would ever be confirmed no matter how long they waited unless they paid more.

DISCLAIMER: This is more an academic exercise than a practical suggestion.  Despite all the FUD I think when the fork happens the other chain will simply die off.  I would strongly discourage performing this unless you completely understand the concept of transaction validity across parallel forks.  If you think Bitcoin works on addresses and balances you will probably lose your Bitcoins on both forks by creating txns which are valid on both forks.