Re: [bitcoin-dev] tx max fee

From: Andrew Baine <andrew.baine@gmail•com>
To: Kalle Rosenbaum <kalle@rosenbaum•se>,
	 Bitcoin Protocol Discussion
	<bitcoin-dev@lists•linuxfoundation.org>
Subject: Re: [bitcoin-dev] tx max fee
Date: Thu, 11 May 2023 11:20:43 -0400	[thread overview]
Message-ID: <CAJxsMutH_QN8pEQFv0y8771goJWuP0ZJiV9fWZX_SH1kdTf6Cg@mail.gmail.com> (raw)
In-Reply-To: <CAPswA9wXFzXmkVvczidt=2Eah0dNgRHdMwgvT22m=m6ffPxb9w@mail.gmail.com>

[-- Attachment #1: Type: text/plain, Size: 8144 bytes --]

Regardless of the submitter's rationale, it is easy to work around any rule
that denies mempool inclusion based on fee proportion: if you have plenty,
add inputs from your own wallet and return to yourself; if not, borrow them
and return to the lender, maybe with interest.

On Thu, May 11, 2023 at 9:27 AM Kalle Rosenbaum via bitcoin-dev <
bitcoin-dev@lists•linuxfoundation.org> wrote:

> Another use case for paying more fees than outputs is to incentivize
> honest mining when Bitcoin is under a state-level censorship attack.
> If it's really important to me that my transaction goes through, I
> might be willing to set a fee at 99x the output value. It's the only
> way bitcoin could work in an adversarial environment.
>
> /Kalle
>
> On Thu, 11 May 2023 at 13:55, vjudeu via bitcoin-dev
> <bitcoin-dev@lists•linuxfoundation.org> wrote:
> >
> > > confused.   the rule was "cannot pay a fee > sum of outputs with
> consideration of cpfp in the mempool"
> > > your example is of someone paying a fee "< sum"  which wouldn't be
> blocked
> >
> > Every transaction paying "fee > sum" can be replaced by N transactions
> paying "fee <= sum", where the sum of all fees will be the same. That
> means, someone will still do the same thing, but it will be just expanded
> into N transactions, so you will reach the same outcome, but splitted into
> more transactions. That means, mempool will be even more congested, because
> for example instead of 1kB transaction with huge fee, you will see 100 such
> transactions with smaller fees, that will add to the same amount, but will
> just consume more space.
> >
> > > show me how someone could move 1 btc and pay 2 btc as fees...
> >
> > In the previous example, I explained how someone could move 1k sats and
> pay almost 1 BTC as fees. But again, assuming that you have 3 BTC, and you
> move 1 BTC with 2 BTC fee, that will be rejected by your rules if and only
> if that will be done in a single transaction. But hey, the same owner can
> prepare N transactions upfront, and release them all at the same time,
> Segwit makes it possible without worrying about malleability.
> >
> > So, instead of:
> >
> > 3 BTC -> 1 BTC
> >
> > You can see this:
> >
> > 3 BTC -> 2 BTC -> 1 BTC
> >
> > If that second transaction will not pass CPFP, more outputs could be
> used:
> >
> > +--------------------+--------------------+--------------------+
> > | 3.0 BTC -> 0.5 BTC | 0.5 BTC -> 0.5 BTC | 0.5 BTC -> 0.5 BTC |
> > |            0.5 BTC | 0.5 BTC    0.5 BTC | 0.5 BTC            |
> > |            0.5 BTC | 0.5 BTC            +--------------------+
> > |                    +--------------------+
> > |            0.5 BTC | 0.5 BTC -> 0.5 BTC |
> > |            0.5 BTC | 0.5 BTC            |
> > +--------------------+--------------------+
> >
> > As you can see, there are four transactions, each paying 0.5 BTC fee, so
> the total fee is 2 BTC. However, even if you count it as CPFP, you will get
> 1.5 BTC in fees for the third transaction in the chain. Note that more
> outputs could be used, or they could be wired a bit differently, and then
> if you will look at the last transaction, the sum of all fees from 10 or 15
> transactions in that chain, could still pass your limits, but the whole
> tree will exceed that. If you have 1.5 BTC limit for that 3 BTC, then you
> could have 20 separate chains of transactions, each paying 0.1 BTC in fees,
> and it will still sum up to 2 BTC.
> >
> > > the only way around it is to maintain balances and use change
> addresses.   which would force nft and timestamp users to maintain these
> balances and would be a deterrent
> >
> > Not really, because you can prepare all of those transactions upfront,
> as the part of your protocol, and release all of them at once. You don't
> have to maintain all UTXOs in between, you can create the whole transaction
> tree first, sign it, and broadcast everything at once. More than that: if
> you have HD wallet, you only need to store a single key, and generate all
> addresses in-between on-the-fly, as needed. Or even use some algorithm to
> deterministically recreate the whole transaction tree.
> >
> >
> >
> > On 2023-05-10 19:42:49 user Erik Aronesty <erik@q32•com> wrote:
> > confused.   the rule was "cannot pay a fee > sum of outputs with
> consideration of cpfp in the mempool"
> >
> >
> > your example is of someone paying a fee "< sum"  which wouldn't be
> blocked
> >
> >
> > note: again, i'm not a fan of this, i like the discussion of "bitcoin as
> money only" and using fee as a lever to do that
> >
> >
> > show me how someone could move 1 btc and pay 2 btc as fees... i think we
> can block it at the network or even the consensus layer, and leave anything
> but "non-monetary use cases" intact.   the only way around it is to
> maintain balances and use change addresses.   which would force nft and
> timestamp users to maintain these balances and would be a deterrent
> >
> >
> > im am much more in favor of doing something like op_ctv which allows
> many users to pool fees and essentially "share" a single utxo.
> > .
> >
> >
> >
> > On Wed, May 10, 2023 at 12:19 PM <vjudeu@gazeta•pl> wrote:
> >
> > > possible to change tx "max fee"  to output amounts?
> >
> > Is it possible? Yes. Should we do that? My first thought was "maybe",
> but after thinking more about it, I would say "no", here is why:
> >
> > Starting point: 1 BTC on some output.
> > Current situation: A single transaction moving 0.99999000 BTC as fees,
> and creating 1000 satoshis as some output (I know, allowed dust values are
> lower and depend on address type, but let's say it is 1k sats to make
> things simpler).
> >
> > And then, there is a room for other solutions, for example your rule,
> mentioned in other posts, like this one:
> https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2023-May/021626.html
> >
> > > probably easier just to reject any transaction where the fee is higher
> than the sum of the outputs
> >
> > Possible situation after introducing your proposal, step-by-step:
> >
> > 1) Someone wants to move 1 BTC, and someone wants to pay 0.99999000 BTC
> as fees. Assuming your rules are on consensus level, the first transaction
> creates 0.5 BTC output and 0.5 BTC fee.
> > 2) That person still wants to move 0.5 remaining BTC, and still is
> willing to pay 0.49999000 BTC as fees. Guess what will happen: you will see
> another transaction, creating 0.25 BTC output, and paying 0.25 BTC fee.
> > ...
> > N) Your proposal replaced one transaction, consuming maybe one kilobyte,
> with a lot of transactions, doing exactly the same, but where fees are
> distributed between many transactions.
> >
> > Before thinking about improving that system, consider one simple thing:
> is it possible to avoid "max fee rule", no matter in what way it will be
> defined? Because as shown above, the answer seems to be "yes", because you
> can always replace a single transaction moving 1 BTC as fees with multiple
> transactions, each paying one satoshi per virtual byte, and then instead of
> consuming around one kilobyte, it would consume around 1 MvB per 0.01 BTC,
> so 100 MvB per 1 BTC mentioned in the example above.
> >
> >
> >
> > On 2023-05-08 13:55:18 user Erik Aronesty via bitcoin-dev <
> bitcoin-dev@lists•linuxfoundation.org> wrote:
> > possible to change tx "max fee"  to output amounts?
> >
> >
> > seems like the only use case that would support such a tx is spam/dos
> type stuff that satoshi warned about
> >
> >
> > its not a fix for everything, but it seems could help a bit with certain
> attacks
> >
> >
> >
> >
> > _______________________________________________
> > bitcoin-dev mailing list
> > bitcoin-dev@lists•linuxfoundation.org
> > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists•linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>

[-- Attachment #2: Type: text/html, Size: 9869 bytes --]