Re: [bitcoin-dev] Selfish Mining Prevention

From: Moral Agent <ethan.scruples@gmail•com>
To: Andrew K <onelineproof@gmail•com>
Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists•linuxfoundation.org>
Subject: Re: [bitcoin-dev] Selfish Mining Prevention
Date: Fri, 14 Sep 2018 14:00:29 -0400	[thread overview]
Message-ID: <CACiOHGz7hFeGKLmUDvsEp-yjiiEfdCWBeKya0ZDVGCeO+1VgZg@mail.gmail.com> (raw)
In-Reply-To: <CAL8tG=kKwjbR4-rOn8K3-=myW5Nx6ugkyPWTTy9c+r0wrA6i0A@mail.gmail.com>

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Thank you, and my apologies. I should have sent that link just to you and
not put everyone on cc.

On Fri, Sep 14, 2018 at 1:30 PM Andrew <onelineproof@gmail•com> wrote:

> (reposting to whole list instead of just him) @Moral Agent:
> Interesting proposal though it introduces some elements
> of proof of stake so it would be more controversial in my view. Also,
> something needs to be explained about how this would not create an
> attack where difficulty is frequently dropping by 25%, and suddenly we
> find ourselves with a very low difficulty and PoW attacks can easily
> happen. I need to analyse your proposal more, but I prefer to discuss
> it on your blog instead of here just to limit the side topics and
> focus only on my proposal.
>
> No one has yet given me a good reason for why not to support my proposal...
>
> On Fri, Sep 14, 2018 at 2:49 PM, Moral Agent <ethan.scruples@gmail•com>
> wrote:
> > You might be interested in an idea I wrote about that is in a similar
> spirit
> > here:
> >
> >
> https://medium.com/coinmonks/taming-large-miners-with-helper-blocks-6ae67ac242f6
> >
> > From the article:
> >
> > When a block is solved, it randomly selects one satoshi from the utxo set
> > and gives whomever controls that satoshi the power to generate a “Helper
> > Block”. The Helper Block commits to a subset of transactions for
> inclusion
> > in the next block. A miner can accept the Helper Block by including the
> > suggested transactions and giving the associated transaction fees to a
> > payment address specified in the Helper Block. Miners who do not use a
> > Helper Block must satisfy a 25% higher difficulty.
> >
> > On Fri, Sep 14, 2018 at 9:56 AM Andrew via bitcoin-dev
> > <bitcoin-dev@lists•linuxfoundation.org> wrote:
> >>
> >> I discussed this more at bitcointalk:
> >> https://bitcointalk.org/index.php?topic=4998410.0
> >>
> >> The attacks I'm interested in preventing are not only selfish mining
> >> and collusion, but also more subtle attacks like block withholding,
> >> and in general anything that aims to drive out the competition in
> >> order to increase hashrate fraction. I also scrapped the idea of
> >> changing the block subsidies, and I am only focuses on fees.
> >>
> >> You can read more about the motivation and details in the bitcointalk
> >> thread, but my proposal in short would be to add the concept of
> >> "reserve fees". When a user makes a transaction, for each txout
> >> script, they can add parameters that specify the fraction of the total
> >> fee that is held in "reserve" and the time it is held in "reserve"
> >> (can set a limit of 2016 blocks). This "reserve" part of the fee will
> >> be paid to miners if the hashrate rises. So if hashrate is currently h
> >> and peak hashrate (from past year) is p, then for each period (1 day),
> >> a new hashrate is calculated h1, and if h1 > h, then the fraction
> >> (h1-h)/p from the reserve fees created in the past 2016 blocks will be
> >> released to miners for that period (spread out over the 144 blocks in
> >> that period). And this will keep happening as long as hashrate keeps
> >> rising, until the "contract" expires, and the leftover part can be
> >> used by the owner of the unspent output, but it can only be used for
> >> paying fees, not as inputs for future transactions (to save on block
> >> space).
> >>
> >> This should incentivize miners to not drive out the competition, since
> >> if they do, there will be less of these reserve fees given to miners.
> >> Yes in the end the miners will get all the fees, but with rising
> >> hashrate they get an unconditional subsidy that does not require
> >> transactions, thus more space for transactions with fees.
> >>
> >> I can make a formal BIP and pull request, but I need to know if there
> >> is interest in this. Now fees don't play such a large part of the
> >> block reward, but they will get more important, and this change
> >> wouldn't force anything (would be voluntary by each user), just miners
> >> have to agree to it with a soft fork (so they don't spend from the
> >> anyone-can-spend outputs used for reserve fees). Resource requirements
> >> for validation are quite small I believe.
> >>
> >> On Sat, Sep 1, 2018 at 12:11 AM, Andrew <onelineproof@gmail•com> wrote:
> >> > As I understand, selfish mining is an attack where miners collude to
> >> > mine at a lower hashrate then with all miners working independently.
> >> > What are the current strategies used to prevent this and what are the
> >> > future plans?
> >> >
> >> > One idea I have is to let the block reward get "modulated" according
> >> > to peak hashrate. Say p is the peak hashrate for 365 periods (1 year)
> >> > consisting of 144 blocks, h is the hashrate of the last 144 block (1
> >> > day) period, and r is the base subsidy (12.5 BTC currently). You can
> >> > then make the max block reward 0.5 r (1 + h/p). So if hashrate is at
> >> > peak you get the full reward. Otherwise you get less, down to a min of
> >> > 0.5 r.
> >> >
> >> > If miners were to collude to mine at a lower than peak hashrate, then
> >> > they may be able to do it profitably for 144 blocks, but after that,
> >> > the reward would get modulated and it wouldn't be so much in their
> >> > interest to continue mining at the lower hashrate.
> >> >
> >> > What flaws are there with this? I know it could be controversial due
> >> > to easier mining present for early miners, so maybe it would have to
> >> > be done in combination with a new more dynamic difficulty adjustment
> >> > algorithm. But I don't see how hashrate can continue rising
> >> > indefinitely, so a solution should be made for selfish mining.
> >> >
> >> > Also when subsidies stop and a fee market is needed, I guess a portion
> >> > of the fees can be withheld for later if hashrate is not at peak.
> >> >
> >> >
> >> > --
> >> > PGP: B6AC 822C 451D 6304 6A28  49E9 7DB7 011C D53B 5647
> >>
> >>
> >>
> >> --
> >> PGP: B6AC 822C 451D 6304 6A28  49E9 7DB7 011C D53B 5647
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>
>
>
> --
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>

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