Date: Wed, 30 Sep 2020 23:44:59 +0000
To: Mike Brooks <m@ib.tc>
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Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>,
 Mike Brooks <f@in.st.capital>
Subject: Re: [bitcoin-dev] Floating-Point Nakamoto Consensus
Precedence: list

Good morning Mike,

An observation to be made is that the current "first seen" is more incentiv=
e-compatible than floating-point Nakamoto consensus.

If a miner A mines a block at height N, then obviously the first block it h=
as seen is that block.

If due to propagation delays on the network, another miner B mines an alter=
native block (let us say with more fitness score, regardless of the details=
 of the fitness metric you use) at height N, miner A has no incentive to re=
ject its own version of that block and mine on top of the miner B alternati=
ve version, even if floating-point Nakamoto consensus is deployed by most n=
odes.

Even if the rest of the mining network is now mining on top of the miner B =
version, if miner A chances on another new block at N+1 built on top of its=
 own version of block N, then it would still win both blocks and earn the b=
lock subsidy and fees of two blocks.
And since block height, as I understand it, trumps over floating-point Naka=
moto consensus, the B version will be reorganized out anyway in that case.
If miner A had switched to mining on top of the miner B block, then if it w=
on another block at height N+1, it would have lost the block subsidy+fees o=
f the lower-scoring miner A block at height N.


Thus, floating-point Nakamoto consensus is not incentive-compatible, so I d=
oubt it would have any kind of adoption.


The problems with stability you mention can be fixed, fairly trivially, by =
simply waiting for 3 confirmations rather than just 1 confirmation.


In a relativistic universe, information cannot propagate faster than light-=
speed, and thus there will always be a communications network delay in prop=
agating data.
As I see it, floating-point Nakamoto consensus cannot fix this issue, as it=
 cannot change underlying laws of the universe.

If your goal is "stability" of some kind, then there is still always a poss=
ibility that two miners on opposite sides of the Earth will create blocks a=
t the same height outside of the light cones of each other.
In a relativistic universe, this cannot be eliminated unless all miners occ=
upy the same physical location, i.e. have centralized in the same mining ha=
rdware.

One of those two blocks created will, with high probability, have a lower s=
core, and thus any nodes in the light cone of the miner of the lower-scored=
 block will still experience a reorg, as they will first see one block, the=
n switch to the higher-scored block when it arrives to them.

Thus, floating-point Nakamoto consensus cannot provide complete stability o=
f the network, still, as the universe we operate in does not have instantan=
eous information transfer.

A wise designer of automated systems will ***still*** wait for 3 confirmati=
ons before doing anything, and by then, the effects of floating-point Nakam=
oto consensus will be literally a thing of the past.


Regards,
ZmnSCPxj