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From: Me <jimmyjack@gmail.com>
In-Reply-To: <55A7BFF7.2050608@xylon.de>
Date: Thu, 16 Jul 2015 07:50:16 -0700
Message-Id: <57C28E34-7B1C-4501-BB9C-5727862023F3@gmail.com>
References: <24662b038abc45da7f3990e12a649b8a@airmail.cc>
	<55A7BFF7.2050608@xylon.de>
To: Arne Brutschy <abrutschy@xylon.de>
Cc: bitcoin-dev@lists.linuxfoundation.org
Subject: Re: [bitcoin-dev] Significant losses by double-spending unconfirmed
	transactions
Precedence: list


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> minrelaytxfee setting proposed in the 0.11.0 release notes

my guess, he is talking about this =
https://bitcoin.org/en/glossary/minimum-relay-fee =
<https://bitcoin.org/en/glossary/minimum-relay-fee> - slam dunk =
technique for doublespend



> Related: is there somewhere a chart that plots `estimatefee` over
> time? Would be interesting to see how the fee market evolved over
> these past weeks.

I find this useful
https://bitcoinfees.github.io/ <https://bitcoinfees.github.io/>





> On Jul 16, 2015, at 7:30 AM, Arne Brutschy via bitcoin-dev =
<bitcoin-dev@lists.linuxfoundation.org> wrote:
>=20
> Hello,
>=20
> What are these pre- and post-Hearn-relay drop rules you are speaking
> about? Can anybody shed some light on this? (I am aware of the
> minrelaytxfee setting proposed in the 0.11.0 release notes, I just
> don't see what this has to do with Mike Hearn, BitcoinXT, and whether
> there's a code change related to this that I missed).
>=20
> Related: is there somewhere a chart that plots `estimatefee` over
> time? Would be interesting to see how the fee market evolved over
> these past weeks.
>=20
> Regards
> Arne
>=20
> On 15/07/15 05:29, simongreen--- via bitcoin-dev wrote:
>> With my black hat on I recently performed numerous profitable=20
>> double-spend attacks against zeroconf accepting fools. With my
>> white hat on, I'm warning everyone. The strategy is simple:
>>=20
>> tx1: To merchant, but dust/low-fee/reused-address/large-size/etc.=20
>> anything that miners don't always accept.
>>=20
>> tx2: After merchant gives up valuable thing in return, normal tx
>> without triggering spam protections. (loltasticly a Mike Hearn
>> Bitcoin XT node was used to relay the double-spends)
>>=20
>> Example success story: tx1 paying Shapeshift.io with 6uBTC output
>> is not dust under post-Hearn-relay-drop rules, but is dust under=20
>> pre-Hearn-relay-drop rules, followed by tx2 w/o the output and not=20
>> paying Shapeshift.io. F2Pool/Eligius/BTCChina/AntPool etc. are all=20
>> miners who have reverted Hearn's 10x relay fee drop as recommended
>> by v0.11.0 release notes and accept these double-spends.
>> Shapeshift.io lost ~3 BTC this week in multiple txs. (they're no
>> longer accepting zeroconf)
>>=20
>> Example success story #2: tx1 with post-Hearn-relay drop fee,
>> followed by tx2 with higher fee. Such stupidly low fee txs just
>> don't get mined, so wait for a miner to mine tx2. Bought a silly
>> amount of reddit gold off Coinbase this way among other things. I'm
>> surprised that reddit didn't cancel the "fools-gold" after tx
>> reversal. (did Coinbase guarantee those txs?) Also found multiple
>> Bitcoin ATMs vulnerable to this attack. (but simulated attack with
>> tx2s still paying ATM because didn't want to go to trouble of good
>> phys opsec)
>>=20
>> Shoutouts to BitPay who did things right and notified merchant
>> properly when tx was reversed.
>>=20
>> In summary, every target depending on zeroconf vulnerable and lost=20
>> significant sums of money to totally trivial attacks with high=20
>> probability. No need for RBF to do this, just normal variations in
>> miner policy. Shapeshift claims to use Super Sophisticated Network
>> Sybil Attacking Monitoring from Blockcypher, but relay nodes !=3D
>> miner policy.
>>=20
>> Consider yourself warned! My hat is whiter than most, and my skills
>> not particularly good.
>>=20
>> What to do? Users: Listen to the experts and stop relying on
>> zeroconf. Black hats: Profit!
>>=20
>> _______________________________________________ bitcoin-dev mailing
>> list bitcoin-dev@lists.linuxfoundation.org=20
>> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>=20
> --=20
> Arne Brutschy <abrutschy@xylon.de>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev


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<html><head><meta http-equiv=3D"Content-Type" content=3D"text/html =
charset=3Dus-ascii"></head><body style=3D"word-wrap: break-word; =
-webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" =
class=3D""><div class=3D""><blockquote type=3D"cite" =
class=3D"">minrelaytxfee setting proposed in the 0.11.0 release =
notes</blockquote></div><div class=3D"">my guess, he is talking about =
this&nbsp;<a href=3D"https://bitcoin.org/en/glossary/minimum-relay-fee" =
class=3D"">https://bitcoin.org/en/glossary/minimum-relay-fee</a>&nbsp;- =
slam dunk technique for doublespend</div><div class=3D""><br =
class=3D""></div><div class=3D""><br class=3D""></div><div class=3D""><br =
class=3D""></div><div class=3D""><blockquote type=3D"cite" =
class=3D"">Related: is there somewhere a chart that plots `estimatefee` =
over<br class=3D"">time? Would be interesting to see how the fee market =
evolved over<br class=3D"">these past weeks.</blockquote><br =
class=3D""></div><div class=3D"">I find this useful</div><a =
href=3D"https://bitcoinfees.github.io/" =
class=3D"">https://bitcoinfees.github.io/</a><div class=3D""><br =
class=3D""></div><div class=3D""><br class=3D""></div><div class=3D""><br =
class=3D""></div><div class=3D""><br class=3D""></div><div class=3D""><br =
class=3D""><div><blockquote type=3D"cite" class=3D""><div class=3D"">On =
Jul 16, 2015, at 7:30 AM, Arne Brutschy via bitcoin-dev &lt;<a =
href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" =
class=3D"">bitcoin-dev@lists.linuxfoundation.org</a>&gt; wrote:</div><br =
class=3D"Apple-interchange-newline"><div class=3D""><div =
class=3D"">Hello,<br class=3D""><br class=3D"">What are these pre- and =
post-Hearn-relay drop rules you are speaking<br class=3D"">about? Can =
anybody shed some light on this? (I am aware of the<br =
class=3D"">minrelaytxfee setting proposed in the 0.11.0 release notes, I =
just<br class=3D"">don't see what this has to do with Mike Hearn, =
BitcoinXT, and whether<br class=3D"">there's a code change related to =
this that I missed).<br class=3D""><br class=3D"">Related: is there =
somewhere a chart that plots `estimatefee` over<br class=3D"">time? =
Would be interesting to see how the fee market evolved over<br =
class=3D"">these past weeks.<br class=3D""><br class=3D"">Regards<br =
class=3D"">Arne<br class=3D""><br class=3D"">On 15/07/15 05:29, =
simongreen--- via bitcoin-dev wrote:<br class=3D""><blockquote =
type=3D"cite" class=3D"">With my black hat on I recently performed =
numerous profitable <br class=3D"">double-spend attacks against zeroconf =
accepting fools. With my<br class=3D"">white hat on, I'm warning =
everyone. The strategy is simple:<br class=3D""><br class=3D"">tx1: To =
merchant, but dust/low-fee/reused-address/large-size/etc. <br =
class=3D"">anything that miners don't always accept.<br class=3D""><br =
class=3D"">tx2: After merchant gives up valuable thing in return, normal =
tx<br class=3D"">without triggering spam protections. (loltasticly a =
Mike Hearn<br class=3D"">Bitcoin XT node was used to relay the =
double-spends)<br class=3D""><br class=3D"">Example success story: tx1 =
paying <a href=3D"http://shapeshift.io" class=3D"">Shapeshift.io</a> =
with 6uBTC output<br class=3D"">is not dust under post-Hearn-relay-drop =
rules, but is dust under <br class=3D"">pre-Hearn-relay-drop rules, =
followed by tx2 w/o the output and not <br class=3D"">paying <a =
href=3D"http://shapeshift.io" class=3D"">Shapeshift.io</a>. =
F2Pool/Eligius/BTCChina/AntPool etc. are all <br class=3D"">miners who =
have reverted Hearn's 10x relay fee drop as recommended<br class=3D"">by =
v0.11.0 release notes and accept these double-spends.<br class=3D""><a =
href=3D"http://shapeshift.io" class=3D"">Shapeshift.io</a> lost ~3 BTC =
this week in multiple txs. (they're no<br class=3D"">longer accepting =
zeroconf)<br class=3D""><br class=3D"">Example success story #2: tx1 =
with post-Hearn-relay drop fee,<br class=3D"">followed by tx2 with =
higher fee. Such stupidly low fee txs just<br class=3D"">don't get =
mined, so wait for a miner to mine tx2. Bought a silly<br =
class=3D"">amount of reddit gold off Coinbase this way among other =
things. I'm<br class=3D"">surprised that reddit didn't cancel the =
"fools-gold" after tx<br class=3D"">reversal. (did Coinbase guarantee =
those txs?) Also found multiple<br class=3D"">Bitcoin ATMs vulnerable to =
this attack. (but simulated attack with<br class=3D"">tx2s still paying =
ATM because didn't want to go to trouble of good<br class=3D"">phys =
opsec)<br class=3D""><br class=3D"">Shoutouts to BitPay who did things =
right and notified merchant<br class=3D"">properly when tx was =
reversed.<br class=3D""><br class=3D"">In summary, every target =
depending on zeroconf vulnerable and lost <br class=3D"">significant =
sums of money to totally trivial attacks with high <br =
class=3D"">probability. No need for RBF to do this, just normal =
variations in<br class=3D"">miner policy. Shapeshift claims to use Super =
Sophisticated Network<br class=3D"">Sybil Attacking Monitoring from =
Blockcypher, but relay nodes !=3D<br class=3D"">miner policy.<br =
class=3D""><br class=3D"">Consider yourself warned! My hat is whiter =
than most, and my skills<br class=3D"">not particularly good.<br =
class=3D""><br class=3D"">What to do? Users: Listen to the experts and =
stop relying on<br class=3D"">zeroconf. Black hats: Profit!<br =
class=3D""><br class=3D"">_______________________________________________ =
bitcoin-dev mailing<br class=3D"">list <a =
href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" =
class=3D"">bitcoin-dev@lists.linuxfoundation.org</a> <br class=3D""><a =
href=3D"https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev" =
class=3D"">https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev<=
/a><br class=3D""></blockquote><br class=3D"">-- <br class=3D"">Arne =
Brutschy &lt;<a href=3D"mailto:abrutschy@xylon.de" =
class=3D"">abrutschy@xylon.de</a>&gt;<br =
class=3D"">_______________________________________________<br =
class=3D"">bitcoin-dev mailing list<br class=3D""><a =
href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" =
class=3D"">bitcoin-dev@lists.linuxfoundation.org</a><br =
class=3D"">https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev<=
br class=3D""></div></div></blockquote></div><br =
class=3D""></div></body></html>=

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