Subject: Re: [bitcoin-dev] Reasons to add sync flags to Bitcoin

From: Tier Nolan <[email-masked]>
Date: Tue, 26 Jul 2016 22:45:14 +0100

On Tue, Jul 26, 2016 at 9:58 PM, Martijn Meijering via bitcoin-dev <
[email-masked]> wrote:

> Is there a reason miners would be more likely to engage in selfish
> mining of sync flags than they are now with ordinary blocks?
>

This proposal has the same effect as adding mandatory empty blocks.

POW targeted at 2 minutes means that the POW for the flag is 25% of the
block POW.  That gives a flag every 2 minutes and a block every 8 minutes.

It has the feature that the conversion rate from hashing power to reward is
the same for the flags and the blocks.  A flag get 25% of the reward for
25% of the effort.

A soft fork to add this rule would have a disadvantage relative to a
competing chain.  It would divert 20% of its hashing power to the flag
blocks, which would be ignored by legacy nodes.  The soft fork would need
55% of the hashing power to win the race.

This isn't that big a deal if a 75% activation threshold is used.  It might
be worth bumping it up to 80% in that case.

This rule would mean that headers first clients would have to download more
information to verify the longest chain.  If they only download the
headers, they are missing 20% of the POW.