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From: Lloyd Fournier <lloyd.fourn@gmail.com>
Date: Tue, 15 Jun 2021 10:59:12 +1000
Message-ID: <CAH5Bsr1NxM6WcpagwpmFC=Nn3tzK+H8n-Vx1_ObMGEejnD4SjA@mail.gmail.com>
To: Antoine Riard <antoine.riard@gmail.com>
Content-Type: multipart/alternative; boundary="00000000000009019105c4c37d55"
Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] A Stroll through Fee-Bumping Techniques :
 Input-Based vs Child-Pay-For-Parent
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On Tue, 15 Jun 2021 at 02:47, Antoine Riard <antoine.riard@gmail.com> wrote:

> > This makes a lot of sense as it matches the semantics of what we are
> trying
> to achieve: allow the owner of an output (whether an individual or group)
> to reduce that output's value to pay a higher fee.
>
> Note, I think you're still struggling with some trust issue that anchor
> upgrade is at least eliminating for LN, namely the pre-agreement among a
> group of signers about the effective feerate to use at some unknown time
> point in the future. If you authorize your counterparty for a broadcast at
> feerate X, how do you prevent a broadcast at feerate Y, where Y is far
> under X, thus maliciously burning a lot of your fee-bumping reserve ?
>
> Of course, one mitigation is to make a contribution to a common
> fee-bumping output reserve proportional to what has been contributed as a
> funding collateral. Thus disincentivizing misuse of the common fee-bumping
> reserve in a game-theoretical way. But if you take the example of a LN
> channel, you're now running into another issue. Off-chain balances might
> fluctuate in a way that most of the time, your fee-bumping reserve
> contribution is out-of-proportion with your balance amounts to protect ?
> And as such enduring some significant timevalue bleeding on your
> fee-bumping reserve.
>
> Single-party managed fee-bumping reserve doesn't seem to suffer from this
> drawback ?
>

I claim that what I am suggesting is a single-party managed fee-bumping
system that solves all fee-bumping requirements of lightning without
needing external utxos and without additional interaction or fee
pre-agreement between parties. On the commit tx you have your balance going
exclusively towards you which you can unilaterally reduce to increase the
fee up to whatever threshold you want. With a HTLC or PTLC you also always
have a tx with an output that you can unilaterally drain to bump fee
(either the hltc-success or htlc-timeout). Are you saying that there are
protocols where this would require pre-arrangement or are you saying that
it would require pre-arrangement in lightning for some reason I don't see?

To further emphasise the generality of this idea you can easily imagine a
world where this is enabled on all Bitcoin transactions (of course you have
to stomach tx malleability -- a bit more palatable with ANYPREVOUT
everywhere). Even for a normal wallet-to-wallet payment the receiver could
efficiently increase the tx fee by making a signature under the key of
their output and replacing the original tx without interacting with the
sender who actually provided the funds for the payment.

Cheers,

LL

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<div dir=3D"ltr"><div dir=3D"ltr"><br></div><br><div class=3D"gmail_quote">=
<div dir=3D"ltr" class=3D"gmail_attr">On Tue, 15 Jun 2021 at 02:47, Antoine=
 Riard &lt;<a href=3D"mailto:antoine.riard@gmail.com" target=3D"_blank">ant=
oine.riard@gmail.com</a>&gt; wrote:<br></div><blockquote class=3D"gmail_quo=
te" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204=
);padding-left:1ex"><div dir=3D"ltr">&gt; This makes a lot of sense as it m=
atches the semantics of what we are trying<br>to achieve: allow the owner o=
f an output (whether an individual or group)<br>to reduce that output&#39;s=
 value to pay a higher fee.<br><br>Note, I think you&#39;re still strugglin=
g with some trust issue that anchor upgrade is at least eliminating for LN,=
 namely the pre-agreement among a group of signers about the effective feer=
ate to use at some unknown time point in the future. If you authorize your =
counterparty for a broadcast at feerate X, how do you prevent a broadcast a=
t feerate Y, where Y is far under X, thus maliciously burning a lot of your=
 fee-bumping reserve ?<br><br>Of course, one mitigation is to make a contri=
bution to a common fee-bumping output reserve proportional to what has been=
 contributed as a funding collateral. Thus disincentivizing misuse of the c=
ommon fee-bumping reserve in a game-theoretical way. But if you take the ex=
ample of a LN channel, you&#39;re now running into another issue. Off-chain=
 balances might fluctuate in a way that most of the time, your fee-bumping =
reserve contribution is out-of-proportion with your balance amounts to prot=
ect ? And as such enduring some significant timevalue bleeding on your fee-=
bumping reserve.<br><br>Single-party managed fee-bumping reserve doesn&#39;=
t seem to suffer from this drawback ?<br></div></blockquote><br></div><div =
class=3D"gmail_quote">I claim that what I am suggesting is a single-party m=
anaged fee-bumping system=20
that solves all fee-bumping requirements of lightning without needing exter=
nal utxos and without additional interaction or fee pre-agreement between p=
arties. On the commit tx you have your balance going exclusively towards yo=
u which you can unilaterally reduce to increase the fee up to whatever thre=
shold you want. With a HTLC or PTLC you also always have a tx with an outpu=
t that you can unilaterally drain to bump fee (either the hltc-success or h=
tlc-timeout). Are you saying that there are protocols where this would requ=
ire pre-arrangement or are you saying that it would require pre-arrangement=
 in lightning for some reason I don&#39;t see?<div><div><br></div><div>To f=
urther emphasise the generality of this idea you can easily imagine a world=
 where this is enabled on all Bitcoin transactions (of course you have to s=
tomach tx malleability -- a bit more palatable with ANYPREVOUT everywhere).=
 Even for a normal wallet-to-wallet payment the receiver could efficiently =
increase the tx fee by making a signature under the key of their output and=
 replacing the original tx without interacting with the sender who actually=
 provided the funds for the payment.<br></div><div><br></div><div>Cheers,</=
div><div><br></div><div>LL</div>

</div><div>=C2=A0</div></div></div>

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