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From: "Russell O'Connor" <roconnor@blockstream.io>
Date: Tue, 11 Dec 2018 10:36:59 -0500
Message-ID: <CAMZUoKnnEJ9=w3Q2a__WEd2gMWDxT55G7omRM5DTuaoEdm1H7Q@mail.gmail.com>
To: dave@dtrt.org
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Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Safer sighashes and more granular SIGHASH_NOINPUT
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I don't believe that the default RBF policy works that way.  My
understanding is that current policy requires an absolute fee increase (by
an amount related to incrementalrelayfee).  There have been proposals to
change default RBF policy, however even my proposal <
https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2018-February/015717.html>
still requires a minimal amount of absolute fee increase as a DoS defense.

(I'm reading your comment as attempting to rebroadcast the original
transaction with the same fee amount, with its relatively higher fee-rate).

On Mon, Dec 10, 2018 at 10:00 AM David A. Harding <dave@dtrt.org> wrote:

> On Thu, Dec 06, 2018 at 11:57:09AM -0500, Russell O'Connor via bitcoin-dev
> wrote:
> > One more item to consider is "signature covers witness weight".
> >
> > While signing the witness weight doesn't completely eliminate witness
> > malleability (of the kind that can cause grief for compact blocks), it
> does
> > eliminate the worst kind of witness malleability from the user's
> > perspective, the kind where malicious relay nodes increase the amount of
> > witness data and therefore reduce the overall fee-rate of the
> transaction.
>
> To what degree is this an actual problem?  If the mutated transaction
> pays a feerate at least incremental-relay-fee[1] below the original
> transaction, then the original transaction can be rebroadcast as an RBF
> replacement of the mutated transaction (unless the mutated version has
> been pinned[2]).
>
> -Dave
>
> [1] $ bitcoind -help-debug | grep -A2 incremental
>   -incrementalrelayfee=<amt>
>        Fee rate (in BTC/kB) used to define cost of relay, used for mempool
>        limiting and BIP 125 replacement. (default: 0.00001)
>
> [2]
> https://bitcoin.stackexchange.com/questions/80803/what-is-meant-by-transaction-pinning
>
>

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<div dir=3D"ltr"><div dir=3D"ltr">I don&#39;t believe that the default RBF =
policy works that way.=C2=A0 My understanding is that current policy requir=
es an absolute fee increase (by an amount related to incrementalrelayfee).=
=C2=A0 There have been proposals to change default RBF policy, however even=
 my proposal &lt;<a href=3D"https://lists.linuxfoundation.org/pipermail/bit=
coin-dev/2018-February/015717.html">https://lists.linuxfoundation.org/piper=
mail/bitcoin-dev/2018-February/015717.html</a>&gt; still requires a minimal=
 amount of absolute fee increase as a DoS defense.</div><div dir=3D"ltr"><b=
r></div><div>(I&#39;m reading your comment as attempting to rebroadcast the=
 original transaction with the same fee amount, with its relatively higher =
fee-rate).<br></div><div dir=3D"ltr"><div><br><div class=3D"gmail_quote"><d=
iv dir=3D"ltr">On Mon, Dec 10, 2018 at 10:00 AM David A. Harding &lt;<a hre=
f=3D"mailto:dave@dtrt.org">dave@dtrt.org</a>&gt; wrote:<br></div><blockquot=
e class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px s=
olid rgb(204,204,204);padding-left:1ex">On Thu, Dec 06, 2018 at 11:57:09AM =
-0500, Russell O&#39;Connor via bitcoin-dev wrote:<br>
&gt; One more item to consider is &quot;signature covers witness weight&quo=
t;.<br>
&gt; <br>
&gt; While signing the witness weight doesn&#39;t completely eliminate witn=
ess<br>
&gt; malleability (of the kind that can cause grief for compact blocks), it=
 does<br>
&gt; eliminate the worst kind of witness malleability from the user&#39;s<b=
r>
&gt; perspective, the kind where malicious relay nodes increase the amount =
of<br>
&gt; witness data and therefore reduce the overall fee-rate of the transact=
ion.<br>
<br>
To what degree is this an actual problem?=C2=A0 If the mutated transaction<=
br>
pays a feerate at least incremental-relay-fee[1] below the original<br>
transaction, then the original transaction can be rebroadcast as an RBF<br>
replacement of the mutated transaction (unless the mutated version has<br>
been pinned[2]).<br>
<br>
-Dave<br>
<br>
[1] $ bitcoind -help-debug | grep -A2 incremental<br>
=C2=A0 -incrementalrelayfee=3D&lt;amt&gt;<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0Fee rate (in BTC/kB) used to define cost of rela=
y, used for mempool<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0limiting and BIP 125 replacement. (default: 0.00=
001)<br>
<br>
[2] <a href=3D"https://bitcoin.stackexchange.com/questions/80803/what-is-me=
ant-by-transaction-pinning" rel=3D"noreferrer" target=3D"_blank">https://bi=
tcoin.stackexchange.com/questions/80803/what-is-meant-by-transaction-pinnin=
g</a><br>
<br>
</blockquote></div></div></div></div>

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