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From: Damian Williamson <willtech@live.com.au>
To: oscar <petdog@gmail.com>, Bitcoin Protocol Discussion
	<bitcoin-dev@lists.linuxfoundation.org>
Thread-Topic: [bitcoin-dev] what do you think about having a maximum fee rate?
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Subject: [bitcoin-dev]  what do you think about having a maximum fee rate?
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If all transactions pay the proposed max then fee there are still going to =
be an awful lot of never confirming transactions once the transaction bandw=
idth limit is surpassed, as I suppose that it roughly is now:

https://bitinfocharts.com/comparison/bitcoin-transactions.html


This is what I have been working on as an alternative:

https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-December/01537=
1.html


There is a previous thread, linked later on in the linked thread.


Regards,

Damian Williamson


________________________________
From: bitcoin-dev-bounces@lists.linuxfoundation.org <bitcoin-dev-bounces@li=
sts.linuxfoundation.org> on behalf of oscar via bitcoin-dev <bitcoin-dev@li=
sts.linuxfoundation.org>
Sent: Friday, 22 December 2017 7:26:12 PM
To: bitcoin-dev@lists.linuxfoundation.org
Subject: [bitcoin-dev] what do you think about having a maximum fee rate?

Hello,
I'm not a bitcoin developer, but I'd like to receive feedback on what
I think is a serious problem. Hope I'm not wasting your time.
I'm also sure this was already discussed, but google doesn't give me
any good result.

Let me explain: I think that the current incentive system doesn't
really align with the way miners are distributed (not very
decentralized, due to pools and huge asic producers).
I think big miners are incentivized to spam the network with low(ish)
fee transactions, thereby forcing regular users into paying extremely
high fees to be able to get their transactions confirmed.

Obviously this is the result of insufficient mining decentralization,
but as I will try to show, such an attack could be profitable even if
you are controlling just 5-10% of the hashing power, which could
always be easy for a big player and with some collusion.

Let's look at some numbers: https://i.imgur.com/sCn4eDG.png

[https://i.imgur.com/sCn4eDG.png]


These are 10 blocks mined yesterday, and they all have rewards hugely
exceeding the normal 12.5 mining output. Even taking the lowest value
of 20, it's a nice 60% extra profit for the miner. Let's say you
control 10% of the hashing power, and you spam enough transactions to
fill 144 blocks (1 day's worth) at 50 satoshi/byte, losing just 72 BTC
in fees.

(blocksize-in-bytes * fee-per-byte * Nblocks)/satoshis-in-btc =3D> (1e6
* 50 * 144)/1e8 =3D> 72

At the same time you will discover about 144*0.1=3D14.4 blocks per day.
Assuming the situation we see in the previous screenshot is what
happens when you have a mempool bigger than one day's worth of blocks,
you would get 20-12.5=3D7.5 extra BTC per block, which is 14.4*7.5=3D108
BTC, given your investment of 72 to spam the mempool. 32 btc extra
profit.

The big assumption here is that spamming 1 day of backlog in the
50satoshi/b range will get people to compete enough to push 7.5 btc of
fees in each block, but:

* https://jochen-hoenicke.de/queue/#30d this seems to confirm that
[https://jochen-hoenicke.de/queue/mempool-20170608.png]<https://jochen-hoen=
icke.de/queue/#30d>

Johoe's Mempool Size Statistics - jochen-hoenicke.de/queue<https://jochen-h=
oenicke.de/queue/#30d>
jochen-hoenicke.de
This page displays the number and size of the unconfirmed bitcoin transacti=
ons, also known as the transactions in the mempool. It gives a real-time vi=
ew and shows how ...


about half the mempool is in the 50satoshi/b range or less.
* https://blockchain.info/pools there are miners that control more than 10%
Bitcoin Hashrate Distribution - Blockchain.info<https://blockchain.info/poo=
ls>
blockchain.info
A pie chart showing the hashrate distribution between the major bitcoin min=
ing pools - Blockchain


* if you get enough new real transactions, it's not necessary to spam
a full 144 blocks worth each day, probably just ~50 would be enough,
cutting the spam cost substantially
* other miners could be playing the same game, helping you spam and
further reduce the costs of the attack
* you actually get 10% of the fees back by avoiding mining your spam
transactions in your own blocks
* most of the spam transactions won't actually end up in blocks if
there is enough pressure coming from real usage

This seems to indicate that you would actually get much higher profit
margins than my estimates. **PLEASE** correct me if my calculations or
my assumptions are wrong.

You might also say that doing this would force users out of the
system, decreasing the value of btc and disincentivizing miners from
continuing. On the other hand, a backlogged mempool could create the
impression of high(er) usage and increase scarcity by slowing down
movements, which could actually push the price upwards.

Of course, it's impossible to prove that this is happening. But the
fact that it is profitable makes me believe that it is happening.

I see some solutions to this, all with their own downsides:

- increasing block size every time there is sustained pressure
this attack wouldn't work, but the downsides have already been
discussed to death.

- change POW
Not clear it would fix this, aside from stimulating terrible
infighting. Controlling 5 to 10% of the hashing power seems too easy,
and I don't think it would be practical to change pow every time that
happens, as it would prevent the development of a solid POW support.

- protocol level MAX transaction fee
I personally think this would totally invalidate the attack by making
the spam more expensive than the fees you would recover.
There already is a minimum fee accepted by the nodes, at 1 satoshi per
byte. The maximum fee could be N times the minimum, maybe 100-200.
Meaning a maximum of 1-2btc in total fee rewards when the block size
is 1mb. Of course the actual values need more analysis, but 2btc -
together with the deflationary structure - seems enough to continue
motivating miners, without giving unfair advantage.

Yes, this would make it impossible to spend your way out of a
congested mempool. But if the mempool stays congested after this
change, you could have a bigger confidence that it's coming from real
usage or from someone willfully burning money, making a block size
increase much more justified.

Hope to hear your opinion,
have a nice day.

oscar
_______________________________________________
bitcoin-dev mailing list
bitcoin-dev@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
bitcoin-dev Info Page - Linux Foundation<https://lists.linuxfoundation.org/=
mailman/listinfo/bitcoin-dev>
lists.linuxfoundation.org
Bitcoin development and protocol discussion. This list is lightly moderated=
. - No offensive posts, no personal attacks. - Posts must concern developme=
nt of bitcoin ...



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<head>
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1">
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n-bottom:0;} --></style>
</head>
<body dir=3D"ltr">
<div id=3D"divtagdefaultwrapper" style=3D"font-size:12pt;color:#000000;font=
-family:Calibri,Helvetica,sans-serif;" dir=3D"ltr">
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oe UI Symbol&quot;,&quot;Android Emoji&quot;,EmojiSymbols;" dir=3D"ltr">
<p style=3D"margin-top:0;margin-bottom:0">If all transactions pay the propo=
sed max then fee there are still going to be an awful lot of never confirmi=
ng transactions once the transaction bandwidth limit is surpassed, as I sup=
pose that it roughly is now:</p>
<p style=3D"margin-top:0;margin-bottom:0"><a href=3D"https://bitinfocharts.=
com/comparison/bitcoin-transactions.html" class=3D"OWAAutoLink" id=3D"LPlnk=
510700" previewremoved=3D"true">https://bitinfocharts.com/comparison/bitcoi=
n-transactions.html</a><br>
</p>
<p style=3D"margin-top:0;margin-bottom:0"><br>
</p>
<p style=3D"margin-top:0;margin-bottom:0">This is what I have been working =
on as an alternative:</p>
<p style=3D"margin-top:0;margin-bottom:0"><a href=3D"https://lists.linuxfou=
ndation.org/pipermail/bitcoin-dev/2017-December/015371.html" class=3D"OWAAu=
toLink" id=3D"LPlnk273833" previewremoved=3D"true">https://lists.linuxfound=
ation.org/pipermail/bitcoin-dev/2017-December/015371.html</a><br>
</p>
<p style=3D"margin-top:0;margin-bottom:0"><br>
</p>
<p style=3D"margin-top:0;margin-bottom:0">There is a previous thread, linke=
d later on in the linked thread.</p>
<p style=3D"margin-top:0;margin-bottom:0"><br>
</p>
<p style=3D"margin-top:0;margin-bottom:0">Regards,</p>
<p style=3D"margin-top:0;margin-bottom:0">Damian Williamson<br>
</p>
<p style=3D"margin-top:0;margin-bottom:0"><br>
</p>
</div>
<hr style=3D"display:inline-block;width:98%" tabindex=3D"-1">
<div id=3D"divRplyFwdMsg" dir=3D"ltr"><font style=3D"font-size:11pt" face=
=3D"Calibri, sans-serif" color=3D"#000000"><b>From:</b> bitcoin-dev-bounces=
@lists.linuxfoundation.org &lt;bitcoin-dev-bounces@lists.linuxfoundation.or=
g&gt; on behalf of oscar via bitcoin-dev &lt;bitcoin-dev@lists.linuxfoundat=
ion.org&gt;<br>
<b>Sent:</b> Friday, 22 December 2017 7:26:12 PM<br>
<b>To:</b> bitcoin-dev@lists.linuxfoundation.org<br>
<b>Subject:</b> [bitcoin-dev] what do you think about having a maximum fee =
rate?</font>
<div>&nbsp;</div>
</div>
<div class=3D"BodyFragment"><font size=3D"2"><span style=3D"font-size:11pt;=
">
<div class=3D"PlainText">Hello,<br>
I'm not a bitcoin developer, but I'd like to receive feedback on what<br>
I think is a serious problem. Hope I'm not wasting your time.<br>
I'm also sure this was already discussed, but google doesn't give me<br>
any good result.<br>
<br>
Let me explain: I think that the current incentive system doesn't<br>
really align with the way miners are distributed (not very<br>
decentralized, due to pools and huge asic producers).<br>
I think big miners are incentivized to spam the network with low(ish)<br>
fee transactions, thereby forcing regular users into paying extremely<br>
high fees to be able to get their transactions confirmed.<br>
<br>
Obviously this is the result of insufficient mining decentralization,<br>
but as I will try to show, such an attack could be profitable even if<br>
you are controlling just 5-10% of the hashing power, which could<br>
always be easy for a big player and with some collusion.<br>
<br>
Let's look at some numbers: <a href=3D"https://i.imgur.com/sCn4eDG.png" id=
=3D"LPlnk393353" previewremoved=3D"true">
https://i.imgur.com/sCn4eDG.png</a>
<p><img style=3D"max-width: 99.9%;" src=3D"https://i.imgur.com/sCn4eDG.png"=
></p>
<br>
<br>
These are 10 blocks mined yesterday, and they all have rewards hugely<br>
exceeding the normal 12.5 mining output. Even taking the lowest value<br>
of 20, it's a nice 60% extra profit for the miner. Let's say you<br>
control 10% of the hashing power, and you spam enough transactions to<br>
fill 144 blocks (1 day's worth) at 50 satoshi/byte, losing just 72 BTC<br>
in fees.<br>
<br>
(blocksize-in-bytes * fee-per-byte * Nblocks)/satoshis-in-btc =3D&gt; (1e6<=
br>
* 50 * 144)/1e8 =3D&gt; 72<br>
<br>
At the same time you will discover about 144*0.1=3D14.4 blocks per day.<br>
Assuming the situation we see in the previous screenshot is what<br>
happens when you have a mempool bigger than one day's worth of blocks,<br>
you would get 20-12.5=3D7.5 extra BTC per block, which is 14.4*7.5=3D108<br=
>
BTC, given your investment of 72 to spam the mempool. 32 btc extra<br>
profit.<br>
<br>
The big assumption here is that spamming 1 day of backlog in the<br>
50satoshi/b range will get people to compete enough to push 7.5 btc of<br>
fees in each block, but:<br>
<br>
* <a href=3D"https://jochen-hoenicke.de/queue/#30d" id=3D"LPlnk430045" prev=
iewremoved=3D"true">
https://jochen-hoenicke.de/queue/#30d</a> this seems to confirm that
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t;wf_segoe-ui_light&quot;,&quot;Segoe UI Light&quot;,&quot;Segoe WP Light&q=
uot;,&quot;Segoe UI&quot;,&quot;Segoe WP&quot;,Tahoma,Arial,sans-serif; lin=
e-height: 21px;">
<a id=3D"LPUrlAnchor_15140779397670.5020064760957874" style=3D"text-decorat=
ion: none;" href=3D"https://jochen-hoenicke.de/queue/#30d" target=3D"_blank=
">Johoe's Mempool Size Statistics - jochen-hoenicke.de/queue</a></div>
<div id=3D"LPMetadata_15140779397680.9085170575351131" style=3D"margin: 10p=
x 0px 16px; color: rgb(102, 102, 102); font-weight: 400; font-family: &quot=
;wf_segoe-ui_normal&quot;,&quot;Segoe UI&quot;,&quot;Segoe WP&quot;,Tahoma,=
Arial,sans-serif; font-size: 14px; line-height: 14px;">
jochen-hoenicke.de</div>
<div id=3D"LPDescription_15140779397690.7955075301785695" style=3D"display:=
 block; color: rgb(102, 102, 102); font-weight: 400; font-family: &quot;wf_=
segoe-ui_normal&quot;,&quot;Segoe UI&quot;,&quot;Segoe WP&quot;,Tahoma,Aria=
l,sans-serif; font-size: 14px; line-height: 20px; max-height: 100px; overfl=
ow: hidden;" altdesc=3D"This server has a mempool limit of 500 MB. The memp=
ool is currently full and low fee transactions are evicted. =0A=
This page displays the number and size of the unconfirmed bitcoin transacti=
ons, also known as the transactions in the mempool. It gives a real-time vi=
ew and shows how the mempool evolves over the time.&lt;br/&gt;&lt;br/&gt;Th=
e transactions are colored by the amount of fee they pay per byte. The data=
 is generated from my full node and is updated every minute. Note that in b=
itcoin there is no global mempool; every node keeps its own set of unconfir=
med transactions that it has seen. The mempool is also cleared when I reboo=
t my node.&lt;br/&gt;&lt;br/&gt;The data is separated into different fee le=
vels given in satoshi per bytes. The lowest colored stripe is for transacti=
ons that pay the lowest fee. Higher fee transactions are stacked on top of =
it. Since miners prefer high fee transactions, a new block usually only rem=
oves the top 1000 kB from the queue.">
This page displays the number and size of the unconfirmed bitcoin transacti=
ons, also known as the transactions in the mempool. It gives a real-time vi=
ew and shows how ...</div>
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<br>
about half the mempool is in the 50satoshi/b range or less.<br>
* <a href=3D"https://blockchain.info/pools" id=3D"LPlnk885015" previewremov=
ed=3D"true">
https://blockchain.info/pools</a> there are miners that control more than 1=
0%
<div id=3D"LPBorder_GT_15140779717770.7357731221258164" style=3D"margin-bot=
tom: 20px; overflow: auto; width: 100%; text-indent: 0px;">
<table id=3D"LPContainer_15140779717690.5380671833139536" style=3D"width: 9=
0%; background-color: rgb(255, 255, 255); position: relative; overflow: aut=
o; padding-top: 20px; padding-bottom: 20px; margin-top: 20px; border-top: 1=
px dotted rgb(200, 200, 200); border-bottom: 1px dotted rgb(200, 200, 200);=
" role=3D"presentation" cellspacing=3D"0">
<tbody>
<tr style=3D"border-spacing: 0px;" valign=3D"top">
<td id=3D"TextCell_15140779717700.9245115839792243" style=3D"vertical-align=
: top; position: relative; padding: 0px; display: table-cell;" colspan=3D"2=
">
<div id=3D"LPRemovePreviewContainer_15140779717700.9573351890057202"></div>
<div id=3D"LPExpandDescriptionContainer_15140779717700.8834056602335468"></=
div>
<div id=3D"LPTitle_15140779717700.5524442635790349" style=3D"top: 0px; colo=
r: rgb(0, 120, 215); font-weight: 400; font-size: 21px; font-family: &quot;=
wf_segoe-ui_light&quot;,&quot;Segoe UI Light&quot;,&quot;Segoe WP Light&quo=
t;,&quot;Segoe UI&quot;,&quot;Segoe WP&quot;,Tahoma,Arial,sans-serif; line-=
height: 21px;">
<a id=3D"LPUrlAnchor_15140779717710.8920784365342228" style=3D"text-decorat=
ion: none;" href=3D"https://blockchain.info/pools" target=3D"_blank">Bitcoi=
n Hashrate Distribution - Blockchain.info</a></div>
<div id=3D"LPMetadata_15140779717710.701833965588494" style=3D"margin: 10px=
 0px 16px; color: rgb(102, 102, 102); font-weight: 400; font-family: &quot;=
wf_segoe-ui_normal&quot;,&quot;Segoe UI&quot;,&quot;Segoe WP&quot;,Tahoma,A=
rial,sans-serif; font-size: 14px; line-height: 14px;">
blockchain.info</div>
<div id=3D"LPDescription_15140779717720.47547707574858455" style=3D"display=
: block; color: rgb(102, 102, 102); font-weight: 400; font-family: &quot;wf=
_segoe-ui_normal&quot;,&quot;Segoe UI&quot;,&quot;Segoe WP&quot;,Tahoma,Ari=
al,sans-serif; font-size: 14px; line-height: 20px; max-height: 100px; overf=
low: hidden;" altdesc=3D"The graph below shows the market share of the most=
 popular bitcoin mining pools. It should only be used as a rough estimate a=
nd for various reasons will not be 100% accurate. A large portion of Unknow=
n blocks does not mean an attack on the network, it simply means we have be=
en unable to determine the origin.">
A pie chart showing the hashrate distribution between the major bitcoin min=
ing pools - Blockchain</div>
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<br>
* if you get enough new real transactions, it's not necessary to spam<br>
a full 144 blocks worth each day, probably just ~50 would be enough,<br>
cutting the spam cost substantially<br>
* other miners could be playing the same game, helping you spam and<br>
further reduce the costs of the attack<br>
* you actually get 10% of the fees back by avoiding mining your spam<br>
transactions in your own blocks<br>
* most of the spam transactions won't actually end up in blocks if<br>
there is enough pressure coming from real usage<br>
<br>
This seems to indicate that you would actually get much higher profit<br>
margins than my estimates. **PLEASE** correct me if my calculations or<br>
my assumptions are wrong.<br>
<br>
You might also say that doing this would force users out of the<br>
system, decreasing the value of btc and disincentivizing miners from<br>
continuing. On the other hand, a backlogged mempool could create the<br>
impression of high(er) usage and increase scarcity by slowing down<br>
movements, which could actually push the price upwards.<br>
<br>
Of course, it's impossible to prove that this is happening. But the<br>
fact that it is profitable makes me believe that it is happening.<br>
<br>
I see some solutions to this, all with their own downsides:<br>
<br>
- increasing block size every time there is sustained pressure<br>
this attack wouldn't work, but the downsides have already been<br>
discussed to death.<br>
<br>
- change POW<br>
Not clear it would fix this, aside from stimulating terrible<br>
infighting. Controlling 5 to 10% of the hashing power seems too easy,<br>
and I don't think it would be practical to change pow every time that<br>
happens, as it would prevent the development of a solid POW support.<br>
<br>
- protocol level MAX transaction fee<br>
I personally think this would totally invalidate the attack by making<br>
the spam more expensive than the fees you would recover.<br>
There already is a minimum fee accepted by the nodes, at 1 satoshi per<br>
byte. The maximum fee could be N times the minimum, maybe 100-200.<br>
Meaning a maximum of 1-2btc in total fee rewards when the block size<br>
is 1mb. Of course the actual values need more analysis, but 2btc -<br>
together with the deflationary structure - seems enough to continue<br>
motivating miners, without giving unfair advantage.<br>
<br>
Yes, this would make it impossible to spend your way out of a<br>
congested mempool. But if the mempool stays congested after this<br>
change, you could have a bigger confidence that it's coming from real<br>
usage or from someone willfully burning money, making a block size<br>
increase much more justified.<br>
<br>
Hope to hear your opinion,<br>
have a nice day.<br>
<br>
oscar<br>
_______________________________________________<br>
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lists.linuxfoundation.org</div>
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 block; color: rgb(102, 102, 102); font-weight: 400; font-family: &quot;wf_=
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l,sans-serif; font-size: 14px; line-height: 20px; max-height: 100px; overfl=
ow: hidden;" altdesc=3D"- Generally encouraged: patches, notification of pu=
ll requests, BIP proposals, academic paper announcements. And discussions t=
hat follow. =0A=
- Generally discouraged: shower thoughts, wild speculation, jokes, &#43;1s,=
 non-technical bitcoin issues, rehashing settled topics without new data, m=
oderation concerns.&lt;br/&gt;&lt;br/&gt;Subscribe to bitcoin-dev by fillin=
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Bitcoin development and protocol discussion. This list is lightly moderated=
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