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	<20140820125901.CB71CE043A5@quidecco.de>
Date: Wed, 20 Aug 2014 16:41:03 +0200
Message-ID: <CANEZrP1RzLmSB74xdFZbePAE9nxjR-_hSCGQhNH81vRKSji2AQ@mail.gmail.com>
From: Mike Hearn <mike@plan99.net>
To: Isidor Zeuner <cryptocurrencies@quidecco.de>
Content-Type: multipart/alternative; boundary=001a11332c8ee746630501109728
Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>,
	Ivan Pustogarov <ivan.pustogarov@uni.lu>
Subject: Re: [Bitcoin-development] Proposal: PoW-based throttling of
 addresses (was: Outbound connections rotation)
Precedence: list

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>
> Misbehaving addresses can have their connecting difficulty
> scaled up, which should make it uneconomic to try to DoS the usage of
> Tor exit nodes for connecting to Bitcoin.
>

You can't solve DoS by requiring all clients to do complicated work, all
that means is that weak clients (like users mobile phones and tablets) are
successfully DoSd whereas the attackers botnet of stolen computers sit
there solving PoWs.

The correct way to solve DoS is by having work prioritisation and queueing
mechanisms, then finding ways to distinguish "good" clients from "bad"
clients. Doing this whilst preserving privacy is hard. Long term the only
way to solve it may be to require clients to present some kind of cookie
during resource exhaustion events that prove they've been around for a
while, thus allowing them to jump the queue.

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Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr"><div class=3D"gmail_extra"><div class=3D"gmail_quote"><blo=
ckquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #c=
cc solid;padding-left:1ex">Misbehaving addresses can have their connecting =
difficulty<br>

scaled up, which should make it uneconomic to try to DoS the usage of<br>
Tor exit nodes for connecting to Bitcoin.<br></blockquote><div><br></div><d=
iv>You can&#39;t solve DoS by requiring all clients to do complicated work,=
 all that means is that weak clients (like users mobile phones and tablets)=
 are successfully DoSd whereas the attackers botnet of stolen computers sit=
 there solving PoWs.</div>
<div><br></div><div>The correct way to solve DoS is by having work prioriti=
sation and queueing mechanisms, then finding ways to distinguish &quot;good=
&quot; clients from &quot;bad&quot; clients. Doing this whilst preserving p=
rivacy is hard. Long term the only way to solve it may be to require client=
s to present some kind of cookie during resource exhaustion events that pro=
ve they&#39;ve been around for a while, thus allowing them to jump the queu=
e.</div>
</div></div></div>

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