<p dir="ltr"><br>
On Aug 11, 2015 12:11 AM, "Sergio Demian Lerner" <<a href="mailto:sergio.d.lerner@gmail.com">sergio.d.lerner@gmail.com</a>> wrote:<br>
> What I'm saying is that this ratio may have improved 20x since miners began using the TheBlueMatt relay network, so deteriorating the ratio 2x does not put miners in a unknown future, but in an future which is far better than the state they were a year ago.</p>
<p dir="ltr">It's still worse than doubling the block size, which was your main argument.</p>
<p dir="ltr">> But SPV mining has improved the ratio another 2x (because headers can be pushed even faster, fit in a single network packet, and can do without inv/getdata round-trips because they basically "pay" for the bandwidth usage by its own proof of work). <br>
> With a better wire protocol you can "propagate" a 10 MB block faster that the time it takes currently to propagate an empty block. <br>
> So 10x deterioration of the ratio would be still something acceptable.</p>
<p dir="ltr">So yes, better relay protocols (whether you consider "SPV mining" a form of that or not) reduce the effect of the block size. That does not give any benefit for reduced interblock times.</p>
<p dir="ltr">Your argument seems to be "centralization pressure is not bad now, because it already improved a lot... so we can make it worse again by reducing interblock time"? I disagree that it is not bad, and shorter blocks have other downsides which were already mentioned.</p>
<p dir="ltr">>> Also, you seem to consider SPV mining a good thing?<br>
><br>
> I'm not saying it's a good thing. I'm saying that it's impossible to avoid. It's a real incentive. It must exists so Bitcoin is incentive compatible. We can talk for hours and hours and we won't prevent miners from doing it. I predicted it back in 2013, without even being a miner myself. It's here to stay. Forever. It's a pity Greg chose that awful name of "SPV" mining instead some cool name like "Instant" mining that we could market as Bitcoin latest feature :)</p>
<p dir="ltr">>> It requires trust between miners that know eachother, and fundamentally breaks the security assumption of SPV clients...<br>
><br>
> No is does not.</p>
<p dir="ltr">The SPV security assumption is that no hashrate majority will collude in order to make my transactions incorrectly look confirmed.</p>
<p dir="ltr">With validation-less mining, even a 0.1% hashrate that is part of a group with 60% hashrate is enough to make that happen.</p>
<p dir="ltr">Of course they won't intentionally do that. No other miner would agree to do validation-less mining with them again, making it harder for them to compete. So it is not permissionless: you get higher profitability by making an agreement with the largest hashrate. I think that is a much worse centralization effect than having an optional centralized relay network available... there could even be multiple such networks.</p>
<p dir="ltr">> The incentive follows directly from the cheating cost (the subsidy). Even if I don't know you, I know you wouldn't waste 25 BTC to try to cheat me for 25 BTC with a probability of 1/100, that's for sure. On average, you loose 24.75 BTC per cheat attempt.</p>
<p dir="ltr">Per cheat attempt, or per bug.</p>
<p dir="ltr">> SPV mining incentive will stay until there is no subsidy, as many other incentives. SPV mining also must be there to prevent malicious actors from DoS-ing the relay network. If it's there, then the DoS incentive disappears.<br>
><br>
> Let's code "instant" mining into Bitcoin Core, and do it right.</p>
<p dir="ltr">I thought about this too. Since headers-first it would be trivial to do: if our best header is ahead of our best block, hand out an empty template in createblocktemplate, and we're done.</p>
<p dir="ltr">Unfortunately, Greg Maxwell pointed out that this (even with a time limit) amplifies selfish mining, since I can propagate headers before propagating blocks, in order to make others temporarily work on top of my chain.</p>
<p dir="ltr">> Also as Michael Rudy points out, higher block rate means lower variance, and that's good for miners. Last, as I already said, having a lower average block interval strengthens Bitcoin value proposition, so miners would be delighted that their bitcoins are more worthy.</p>
<p dir="ltr">Only a small constant factor, but yes.</p>
<p dir="ltr">-- <br>
Pieter<br>
</p>