From: Gavin Andresen <gavinandresen@gmail•com>
To: Gregory Maxwell <gmaxwell@gmail•com>
Cc: Bitcoin Dev <bitcoin-dev@lists•linuxfoundation.org>
Subject: Re: [bitcoin-dev] Weak block thoughts...
Date: Wed, 23 Sep 2015 17:37:25 -0400 [thread overview]
Message-ID: <CABsx9T3NFRO5nw3z=jrs0Hu3caVNkkTTTb1ibqR7LMWsoou9RQ@mail.gmail.com> (raw)
In-Reply-To: <CAAS2fgTr-OuL3T6mXX-4xFC_LHnAiogTTcPMbcjsM7WtRisQEQ@mail.gmail.com>
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On Wed, Sep 23, 2015 at 3:24 PM, Gregory Maxwell <gmaxwell@gmail•com> wrote:
> On Wed, Sep 23, 2015 at 3:43 PM, Gavin Andresen via bitcoin-dev
> <bitcoin-dev@lists•linuxfoundation.org> wrote:
> [...]
> > A miner could try to avoid validation work by just taking a weak block
> > announced by somebody else, replacing the coinbase and re-computing the
> > merkle root, and then mining. They will be at a slight disadvantage to
> fully
>
> Take care, here-- if a scheme is used where e.g. the full solution had
> to be exactly identical to a prior weak block then the result would be
> making mining not progress free because bigger miners would have
> disproportionately more access to the weak/strong one/two punch. I
> think what you're thinking here is okay, but it wasn't clear to me if
> you'd caught that particular potential issue.
>
I'm assuming the optimized protocol would be forward-error-coded (e.g.
using IBLTs) and NOT require the full solution (or follow-on weak blocks)
to be exactly the same.
> Avoiding this is why I've always previously described this idea as
> merged mined block DAG (with blocks of arbitrary strength) which are
> always efficiently deferentially coded against prior state. A new
> solution (regardless of who creates it) can still be efficiently
> transmitted even if it differs in arbitrary ways (though the
> efficiency is less the more different it is).
>
Yup, although I don't get the 'merge mined' bit; the weak blocks are
ephemeral, probably purged out of memory as soon as a few full blocks are
found...
> I'm unsure of what approach to take for incentive compatibility
> analysis. In the worst case this approach class has no better delays
> (and higher bandwidth); but it doesn't seem to me to give rise to any
> immediate incrementally strategic behavior (or at least none worse
> than you'd get from just privately using the same scheme).
>
I don't see any incentive problems, either. Worst case is more miners
decide to skip validation and just mine a variation of the
highest-fee-paying weak block they've seen, but that's not a disaster--
invalid blocks will still get rejected by all the non-miners running full
nodes.
If we did see that behavior, I bet it would be a good strategy for a big
hashrate miner to dedicate some of their hashrate to announcing invalid
weak blocks; if you can get your lazy competitors to mine it, then you
win....
--
--
Gavin Andresen
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next prev parent reply other threads:[~2015-09-23 21:37 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-23 15:43 Gavin Andresen
2015-09-23 16:07 ` Bryan Bishop
2015-09-23 19:24 ` Gregory Maxwell
2015-09-23 21:37 ` Gavin Andresen [this message]
2015-09-23 22:16 ` Jonathan Toomim (Toomim Bros)
2015-09-24 1:11 ` Rusty Russell
2015-09-27 1:39 ` Gregory Maxwell
2015-09-27 9:42 ` Tier Nolan
2015-09-27 15:10 ` Kalle Rosenbaum
2015-09-27 19:50 ` Gregory Maxwell
2015-09-28 8:30 ` Kalle Rosenbaum
2015-09-28 13:30 ` Jonathan Toomim (Toomim Bros)
2015-09-23 16:07 ` Btc Drak
2015-09-23 16:28 ` Peter R
2015-09-23 17:40 ` Gavin
2015-09-23 17:49 ` Peter R
2015-09-23 18:48 ` Tier Nolan
2015-09-24 1:32 ` Rusty Russell
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