Subject: Re: [bitcoindev] BIP 8.5: Flag day activation based on nlocktime signaling

From: "'Fabian' via Bitcoin Development Mailing List" <[email-masked]>
Date: Mon, 19 Aug 2024 13:16:48 +0000

Hi,

that would be a NACK from me. I think this idea has many issues, I am just listing the ones that came to my head first:

- Requiring users to make transactions in order to participate in order to signal is problematic because it comes with economic costs to them that depends a lot on their personal setup. What if they have their funds in a vault? Then they have to go through a lengthy and costly process to get them out. Or if they simply timelocked them for a number of years? Then they can not participate at all.
- Motivated spammers can, however, simulate support for low costs if they have the right setup. I would guess spammers have a few UTXOs laying around in hot wallets and would be willing to invest some money if it serves their interests.
- Depending on whether the users pay high or low fees in these signaling transactions, they can choose their own adventure of misaligned incentives...
- If the users pay high fees in these transactions some miners that don't care about this will just mine the transaction not because they want to signal but instead because it serves their economic interest. This means you would need buy-in from all miners (template builders) in the world for this to work on not get seemingly great signaling for these high fee transactions even though the miners just want to earn the fees and may not even know about a softfork proposal.
- If the miners pay low fees still all miners that offer out of band acceleration of transactions would need to buy-in and not allow these transactions to be boosted to prevent manipulation.
- The low fee transactions would still need to be kept in a mempool somewhere to prevent manipulation via eviction from mempools or the signaling transactions simply disappearing. Keeping a transaction in the mempool has many problems which is apparent from all the L2 research that is going into this topic.
- As far as I can tell there are some ordinal protocols that use the lock time field for something, how do you keep these two concepts apart?
- "Community can analyze these transactions" That won't work. What do you define as the lock-in mechanism? I suppose you would count the number of blocks that had at least one signaling transaction in them. Ok, that could work but that would mean that it's really not a lot of transactions that would need to get into blocks via one of the manipulation methods I mentioned above.
- Thinking more about the previous point: Users broadcasting their own transactions with signaling is really just an unnecessary misdirection. If a miner signals by including these transactions in a block it doesn't matter if they include one or 100 of these in a block. A block can just signal or not signal. So it would probably play out in a way that users wouldn't send any signaling transactions and miners would just include a single signaling self payment in their block template. Which then is just a worse way of doing the signaling with the version field.
- I also don't think that the readiness signaling mechanism is actually the reason why bip8/9 are controversial so I don't think your proposal really would make things better even if the signaling part would work well.

That was bit ramblin, so, to summarize the top 3 issues I could come up with off the top of my head why this wouldn't work:

- Miners may "signal" by including high fee transactions even though they don't know about the process at all
- Users (if they would even need/want to participate) would bare economic cost or may even have excluded themselves from the process already without knowing it
- Spammers have many avenues today to exploit this mechanism at minimal cost, all of these loop holes would need to be closed/defended

If you want to follow up please first take a look at the level of detail that BIP8 and BIP9 provide and try to get your proposal at least somewhere close to that level of detail if you want to have it taken serious as a BIP proposal. Otherwise, if this is just an idea or a question then maybe make it a Stack Exchange question or maybe a delving bitcoin post.

And please don't self-assign BIP numbers, it's irritating.

Best,
Fabian
On Monday, August 19th, 2024 at 7:08 AM, /dev /fd0 <[email-masked]> wrote:

> Hi Bitcoin Developers,
>
> I am proposing an alternative way to activate soft forks. Please let me know if you see any issues with this method.
>
> BIP: XXX
> Layer: Consensus (soft fork)
> Title: nLockTime signaling and flag day activation
> Author: /dev/fd0 <[email-masked]>
> Status: Draft
> Type: Standards Track
> Created: 2024-08-19
> License: Public Domain
>
> ## Abstract
>
> This document describes a process to activate soft forks using flag day after `nLockTime` signaling and discussion.
>
> ## Motivation
>
> BIP 8 and BIP 9 are controversial. This BIP is an alternative which addresses the problems with other activation methods.
>
> ## Specification
>
> - Assign numbers to different soft fork proposals or use their BIP numbers
> - Users can broadcast their transactions with one of these numbers used as `nLockTime` to show support
> - Miners inlcuding a transaction in block would signal readiness for a soft fork
> - Community can analyze these transactions after 3 months and prepare for a flag day activation of soft fork
>
> Example:
> Use 119 to signal support for OP_CHECKTEMPLATEVERIFY in `nLockTime`
>
> ## Reference implementation
>
> Activation: https://github.com/bitcoin/bitcoin/commit/ab91bf39b7c11e9c86bb2043c24f0f377f1cf514.diff
>
> Exclusion in relay or mining: https://github.com/bitcoinknots/bitcoin/commit/18cd7b0ef6eaeacd06678c6d192b6cacc9d7eee5.diff
>
> ---
>
> If a transaction does not get included in block for a long time, users can replace it with another transaction spending same inputs and use a different `nLockTime`.
>
> /dev/fd0
> floppy disk guy
>
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