[bitcoin-dev] Introducing a POW through a soft-fork
c1.bitcoin at niftybox.net
Mon Nov 6 22:39:02 UTC 2017
Hi Peter, thank you for the review. See below
On Mon, Nov 6, 2017 at 11:50 AM Peter Todd <pete at petertodd.org> wrote:
> On Wed, Nov 01, 2017 at 05:48:27AM +0000, Devrandom via bitcoin-dev wrote:
> Some quick thoughts...
> > Hi all,
> > Feedback is welcome on the draft below. In particular, I want to see if
> > there is interest in further development of the idea and also interested
> > any attack vectors or undesirable dynamics.
> > (Formatted version available here:
> > https://github.com/devrandom/btc-papers/blob/master/aux-pow.md )
> > # Soft-fork Introduction of a New POW
> First of all, I don't think you can really call this a soft-fork; I'd call
> it a
> My reasoning being that after implementation, a chain with less total work
> the main chain - but more total SHA256^2 work than the main chain - might
> followed by non-supporting clients. It's got some properties of a
> but it's security model is definitely different.
The interesting thing is that the cost of attack varies smoothly as you
vary the POW weights.
To attack non-upgraded nodes, you still have to "51%" the original POW.
The reward going to that POW will vary smoothly between 1.0 * block_reward
target value (e.g. 0.5 * block_reward) and the difficulty of attack will
tend to be proportional to that.
In a real hard-fork, your software just breaks at the fork point. In this
case, it's just the non-upgraded
node security level declining from 100% to 50% over a long period of time.
I envision the transition of POW weights will be over 1-3 years, which
leaves plenty of time to
upgrade after the fork activates.
> > ### Aux POW intermediate block
> > Auxiliary POW blocks are introduced between normal blocks - i.e. the
> > alternates between the two POWs.
> > Each aux-POW block points to the previous normal block and contains
> > transactions just like a normal block.
> > Each normal block points to the previous aux-POW block and must contain
> > transactions from the aux-POW block.
> Note how you're basically proposing for the block interval to be decreased,
> which has security implications due to increased orphan rates.
Note that the total transaction rate and block size don't materially
change, so I don't
see why the orphan rate will change. Normal blocks are constrained to have
all of the txs of the aux blocks, so propagation time should stay the
same. Am I missing
> > ### Heaviest chain rule change
> > This is a semi-hard change, because non-upgraded nodes can get on the
> > chain in case of attack. However,
> Exactly! Not really a soft-fork.
"smooth-fork" perhaps? :)
> https://petertodd.org 'peter'[:-1]@petertodd.org
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