From: "Kenshiro []" <tensiam@hotmail.com>
To: "bitcoin-dev@lists.linuxfoundation.org"
	<bitcoin-dev@lists.linuxfoundation.org>
Thread-Topic: Add a moving checkpoint to the Bitcoin protocol
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Date: Wed, 31 Jul 2019 12:28:58 +0000
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Subject: [bitcoin-dev] Add a moving checkpoint to the Bitcoin protocol
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Hi all,

I would like to propose that a "moving checkpoint" is added to the Bitcoin =
protocol. It's a very simple rule already implemented in NXT coin:

- A node will ignore any new block under nodeBlockHeight - N, so the blockc=
hain becomes truly immutable after N blocks, even during a 51% attack which=
 thanks to the moving checkpoint can't rewrite history older than the last =
N blocks.

NXT coin has a N value of 720 blocks, like 12 hours of blocks.

To be more conservative, Bitcoin could have a N value of 144 blocks (like 2=
4 hours). So users and exchanges could plan their operations with big amoun=
ts of BTC knowing that only after 24 hours a transaction is truly immutable=
.

Maybe a 51% attack never happens but if it does it would be nice to be 100%=
 sure that history rewrite is limited to only 24 hours.

Regards,

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<html>
<head>
<meta http-equiv=3D"Content-Type" content=3D"text/html; charset=3Diso-8859-=
1">
<style type=3D"text/css" style=3D"display:none;"> P {margin-top:0;margin-bo=
ttom:0;} </style>
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<body dir=3D"ltr">
<div style=3D"font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;=
 color: rgb(0, 0, 0);">
Hi all,&nbsp;</div>
<div style=3D"font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;=
 color: rgb(0, 0, 0);">
<br>
</div>
<div style=3D"font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;=
 color: rgb(0, 0, 0);">
I would like to propose that a &quot;moving checkpoint&quot; is added to th=
e Bitcoin protocol. It's a very simple rule already implemented in NXT coin=
:&nbsp;</div>
<div style=3D"font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;=
 color: rgb(0, 0, 0);">
<br>
</div>
<div style=3D"font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;=
 color: rgb(0, 0, 0);">
-&nbsp;A node will ignore any new block under nodeBlockHeight - N, so the b=
lockchain becomes truly immutable after N blocks, even during a 51% attack =
which thanks to the moving checkpoint can't rewrite history older than the =
last N blocks.
</div>
<div style=3D"font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;=
 color: rgb(0, 0, 0);">
<br>
</div>
<div style=3D"font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;=
 color: rgb(0, 0, 0);">
NXT coin has a N value of 720 blocks, like 12 hours of blocks.&nbsp;</div>
<div style=3D"font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;=
 color: rgb(0, 0, 0);">
<br>
</div>
<div style=3D"font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;=
 color: rgb(0, 0, 0);">
To be more conservative, Bitcoin could have a N value of 144 blocks (like 2=
4 hours). So users and exchanges could plan their operations with big amoun=
ts of BTC knowing that only after 24 hours a transaction is truly immutable=
.&nbsp;</div>
<div style=3D"font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;=
 color: rgb(0, 0, 0);">
<br>
</div>
<div style=3D"font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;=
 color: rgb(0, 0, 0);">
Maybe a 51% attack never happens but if it does it would be nice to be 100%=
 sure that history rewrite is limited to only 24 hours.</div>
<div style=3D"font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;=
 color: rgb(0, 0, 0);">
<br>
</div>
<div style=3D"font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;=
 color: rgb(0, 0, 0);">
<span style=3D"color: rgb(0, 0, 0); font-family: Calibri, Helvetica, sans-s=
erif; font-size: 12pt;">Regards,</span><br>
</div>
</body>
</html>

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