Subject: Re: [bitcoindev] Re: Great Consensus Cleanup Revival

From: "'Antoine Poinsot' via Bitcoin Development Mailing List" <[email-masked]>
Date: Thu, 18 Apr 2024 10:04:18 +0000

> You are free to criticize Forward Blocks, but please do so by actually addressing the content of the proposal. Let's please hold a standard of intellectual excellence on this mailing list in which ideas are debated based on content-level arguments rather than repeating inaccurate takes from Reddit/Twitter.

You are the one being dishonest here. Look, i understand you came up with a fun hack exploiting bugs in Bitcoin and you are biased against fixing them. Yet, the cost of not fixing timewarp objectively far exceeds the cost of making "forward blocks" impossible.

As already addressed in the DelvingBitcoin post:

- The timewarp bug significantly changes the 51% attacker threat model. Without exploiting it a censoring miner needs to continuously keep more hashrate than the rest of the network combined for as long as he wants to prevent some people from using Bitcoin. By exploiting timewarp the attacker can prevent everybody from using Bitcoin within 40 days.
- The timewarp bug allows an attacking miner to force on full nodes more block data than they agreed to. This is actually the attack leveraged by your proposal. I believe this variant of the attack is more likely to happen, simply for the reason that all participants of the system have a short term incentive to exploit this (yay lower fees! yay more block subsidy!), at the expense of the long term health of the system. As the block subsidy exponentially decreases miners are likely to start playing more games and that's a particularly attractive one. Given the level of mining centralization we are witnessing [0] i believe this is particularly worrisome.
- I'm very skeptical of arguments about how "we" can stop an attack which requires "weeks of forewarning". Who's we? How do we proceed, all Bitcoin users coordinate and arbitrarily decide of the validity of a block? A few weeks is very little time if this is at all achievable. If you add on top of that the political implications of the previous point it gets particularly messy.

I've got better things to do than to play "you are being dishonest! -no it's you -no you" games. So unless you bring something new to the table this will be my last reply to your accusations.

Antoine

[0] https://x.com/0xB10C/status/1780611768081121700
On Thursday, April 18th, 2024 at 2:46 AM, Mark F <[email-masked]> wrote:

> On Wednesday, March 27, 2024 at 4:00:34 AM UTC-7 Antoine Poinsot wrote:
>
>>> The only beneficial case I can remember about the timewarp issue is "forwarding blocks" by maaku for on-chain scaling:
>>> http://freico.in/forward-blocks-scalingbitcoin-paper.pdf
>>
>> I would not qualify this hack of "beneficial". Besides the centralization pressure of an increased block frequency, leveraging the timewarp to achieve it would put the network constantly on the Brink of being seriously (fatally?) harmed. And this sets pernicious incentives too. Every individual user has a short-term incentive to get lower fees by the increased block space, at the expense of all users longer term. And every individual miner has an incentive to get more block reward at the expense of future miners. (And of course bigger miners benefit from an increased block frequency.)
>
> Every single concern mentioned here is addressed prominently in the paper/presentation for Forward Blocks:
>
> * Increased block frequency is only on the compatibility chain, where the content of blocks is deterministic anyway. There is no centralization pressure from the frequency of blocks on the compatibility chain, as the content of the blocks is not miner-editable in economically meaningful ways. Only the block frequency of the forward block chain matters, and here the block frequency is actually *reduced*, thereby decreasing centralization pressure.
>
> * The elastic block size adjustment mechanism proposed in the paper is purposefully constructed so that users or miners wanting to increase the block size beyond what is currently provided for will have to pay significantly (multiple orders of magnitude) more than they could possibly acquire from larger blocks, and the block size would re-adjust downward shortly after the cessation of that artificial fee pressure.
>
> * Increased block frequency of compatibility blocks has no effect on the total issuance, so miners are not rewarded by faster blocks.
>
> You are free to criticize Forward Blocks, but please do so by actually addressing the content of the proposal. Let's please hold a standard of intellectual excellence on this mailing list in which ideas are debated based on content-level arguments rather than repeating inaccurate takes from Reddit/Twitter.
>
> To the topic of the thread, disabling time-warp will close off an unlikely and difficult to pull off subsidy draining attack that to activate would necessarily require weeks of forewarning and could be easily countered in other ways, with the tradeoff of removing the only known mechanism for upgrading the bitcoin protocol to larger effective block sizes while staying 100% compatible with un-upgraded nodes (all nodes see all transactions).
>
> I think we should keep our options open.
>
> -Mark
>
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