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Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] Long-term mining incentives
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Checkpoints will be replaced by compiled-in 'at THIS timestamp the main chai=
n had THIS much proof of work.'
That is enough information to prevent attacks and still allow optimizations l=
ike skipping signature checking for ancient transactions.
I don't think anybody is proposing replacing checkpoints with nothing.
--
Gavin Andresen
> On May 13, 2015, at 8:26 AM, Alex Mizrahi <alex.mizrahi@gmail.com> wrote:
>=20
> Let's consider a concrete example:
>=20
> 1. User wants to accept Bitcoin payments, as his customers want this.
> 2. He downloads a recent version of Bitcoin Core, checks hashes and so on.=
(Maybe even builds from source.)
> 3. Let's it to sync for several hours or days.
> 4. After wallet is synced, he gives his address to customer.
> 5. Customer pays.=20
> 6. User waits 10 confirmations and ships the goods. (Suppose it's somethin=
g very expensive.)
> 7. Some time later, user wants to convert some of his bitcoins to dollars.=
He sends his bitcoins to an exchange but they never arrive.
>=20
> He tries to investigate, and after some time discovers that his router (or=
his ISP's router) was hijacked. His Bitcoin node couldn't connect to any of=
the legitimate nodes, and thus got a complete fake chain from the attacker.=
> Bitcoins he received were totally fake.
>=20
> Bitcoin Core did a shitty job and confirmed some fake transactions.
> User doesn't care that if his network was not impaired, Bitcoin Core would=
have worked properly.
> The main duty of Bitcoin Core is to check whether transactions are confirm=
ed, and if it can be fooled by a simple router hack, then it does its job po=
orly.
>=20
> If you don't see it being a problem, you should't be allowed to develop an=
ything security-related.
>=20
>> If a node is connected to 99 dishonest nodes and 1 honest node, it can st=
ill sync with the main network.
>=20
> Yes, it is good against Sybil attack, but not good against a network-level=
attack.
> Attack on user's routers is a very realistic, plausible attack.
> Imagine if SSL could be hacked by hacking a router, would people still use=
it?
>=20
> Fucking no.
> =20
>> A 3 month reversal would be devastating, so the checkpoint isn't adding m=
uch extra security.
>=20
> WIthout checkpoints an attacker could prepare a fork for $10.
> With checkpoints, it would cost him at least $1000, but more likely upward=
s of $100000.
> That's quite a difference, no?
>=20
> I do not care what do you think about the reasons why checkpoints were add=
ed, but it is a fact that they make the attack scenario I describe above har=
d to impossible.
>=20
> Without checkpoints, you could perform this attack using a laptop.
> With checkpoints, you need access to significant amounts of mining ASICs.
>=20
> --------------------------------------------------------------------------=
----
> One dashboard for servers and applications across Physical-Virtual-Cloud=20=
> Widest out-of-the-box monitoring support with 50+ applications
> Performance metrics, stats and reports that give you Actionable Insights
> Deep dive visibility with transaction tracing using APM Insight.
> http://ad.doubleclick.net/ddm/clk/290420510;117567292;y
> _______________________________________________
> Bitcoin-development mailing list
> Bitcoin-development@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/bitcoin-development
--Apple-Mail-1D350ADE-A483-4CFC-A151-4F92256CF5F9
Content-Type: text/html;
charset=utf-8
Content-Transfer-Encoding: quoted-printable
<html><head><meta http-equiv=3D"content-type" content=3D"text/html; charset=3D=
utf-8"></head><body dir=3D"auto"><div>Checkpoints will be replaced by compil=
ed-in 'at THIS timestamp the main chain had THIS much proof of work.'</div><=
div><br></div><div>That is enough information to prevent attacks and still a=
llow optimizations like skipping signature checking for ancient transactions=
.</div><div><br></div><div>I don't think anybody is proposing replacing chec=
kpoints with nothing.<br><br>--<div>Gavin Andresen</div><div><br></div></div=
><div><br>On May 13, 2015, at 8:26 AM, Alex Mizrahi <<a href=3D"mailto:al=
ex.mizrahi@gmail.com">alex.mizrahi@gmail.com</a>> wrote:<br><br></div><bl=
ockquote type=3D"cite"><div><div dir=3D"ltr">Let's consider a concrete examp=
le:<div><br></div><div>1. User wants to accept Bitcoin payments, as his cust=
omers want this.</div><div>2. He downloads a recent version of Bitcoin Core,=
checks hashes and so on. (Maybe even builds from source.)</div><div>3. Let'=
s it to sync for several hours or days.</div><div>4. After wallet is synced,=
he gives his address to customer.</div><div>5. Customer pays. </div><d=
iv>6. User waits 10 confirmations and ships the goods. (Suppose it's somethi=
ng very expensive.)</div><div>7. Some time later, user wants to convert some=
of his bitcoins to dollars. He sends his bitcoins to an exchange but they n=
ever arrive.</div><div><br></div><div>He tries to investigate, and after som=
e time discovers that his router (or his ISP's router) was hijacked. His Bit=
coin node couldn't connect to any of the legitimate nodes, and thus got a co=
mplete fake chain from the attacker.</div><div>Bitcoins he received were tot=
ally fake.</div><div><br></div><div>Bitcoin Core did a shitty job and confir=
med some fake transactions.</div><div>User doesn't care that <i>if </i>his n=
etwork was not impaired, Bitcoin Core <i>would have </i>worked properly.</di=
v><div>The main duty of Bitcoin Core is to check whether transactions are co=
nfirmed, and if it can be fooled by a simple router hack, then it does its j=
ob poorly.</div><div><br></div><div>If you don't see it being a problem, you=
should't be allowed to develop anything security-related.</div><div><br></d=
iv><div><div class=3D"gmail_extra"><div class=3D"gmail_quote"><blockquote cl=
ass=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;pa=
dding-left:1ex"><div dir=3D"ltr"><div class=3D"gmail_extra"><div class=3D"gm=
ail_quote"><div>If a node is connected to 99 dishonest nodes and 1 honest no=
de, it can still sync with the main network.<br></div></div></div></div></bl=
ockquote><div><br></div><div>Yes, it is good against Sybil attack, but not g=
ood against a network-level attack.</div><div>Attack on user's routers is a v=
ery realistic, plausible attack.</div><div>Imagine if SSL could be hacked by=
hacking a router, would people still use it?</div><div><br></div><div>Fucki=
ng no.</div><div> </div><blockquote class=3D"gmail_quote" style=3D=
"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir=3D"=
ltr"><div class=3D"gmail_extra"><div class=3D"gmail_quote"><div></div><div>A=
3 month reversal would be devastating, so the checkpoint isn't adding much e=
xtra security.<br></div></div></div></div></blockquote><div><br></div><div>W=
Ithout checkpoints an attacker could prepare a fork for $10.</div><div>With c=
heckpoints, it would cost him at least $1000, but more likely upwards of $10=
0000.</div><div>That's quite a difference, no?</div><div><br></div><div>I do=
not care what do you think about the reasons why checkpoints were added, bu=
t it is a fact that they make the attack scenario I describe above hard to i=
mpossible.</div><div><br></div><div>Without checkpoints, you could perform t=
his attack using a laptop.</div><div>With checkpoints, you need access to si=
gnificant amounts of mining ASICs.</div><div><br></div></div></div></div></d=
iv>
</div></blockquote><blockquote type=3D"cite"><div><span>--------------------=
----------------------------------------------------------</span><br><span>O=
ne dashboard for servers and applications across Physical-Virtual-Cloud </sp=
an><br><span>Widest out-of-the-box monitoring support with 50+ applications<=
/span><br><span>Performance metrics, stats and reports that give you Actiona=
ble Insights</span><br><span>Deep dive visibility with transaction tracing u=
sing APM Insight.</span><br><span><a href=3D"http://ad.doubleclick.net/ddm/c=
lk/290420510;117567292;y">http://ad.doubleclick.net/ddm/clk/290420510;117567=
292;y</a></span></div></blockquote><blockquote type=3D"cite"><div><span>____=
___________________________________________</span><br><span>Bitcoin-developm=
ent mailing list</span><br><span><a href=3D"mailto:Bitcoin-development@lists=
.sourceforge.net">Bitcoin-development@lists.sourceforge.net</a></span><br><s=
pan><a href=3D"https://lists.sourceforge.net/lists/listinfo/bitcoin-developm=
ent">https://lists.sourceforge.net/lists/listinfo/bitcoin-development</a></s=
pan><br></div></blockquote></body></html>=
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