1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
|
Return-Path: <pete@petertodd.org>
Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org
[172.17.192.35])
by mail.linuxfoundation.org (Postfix) with ESMTPS id 35EE8E37
for <bitcoin-dev@lists.linuxfoundation.org>;
Sat, 19 Dec 2015 18:42:47 +0000 (UTC)
X-Greylist: from auto-whitelisted by SQLgrey-1.7.6
Received: from outmail149081.authsmtp.net (outmail149081.authsmtp.net
[62.13.149.81])
by smtp1.linuxfoundation.org (Postfix) with ESMTP id 63589159
for <bitcoin-dev@lists.linuxfoundation.org>;
Sat, 19 Dec 2015 18:42:46 +0000 (UTC)
Received: from mail-c247.authsmtp.com (mail-c247.authsmtp.com [62.13.128.247])
by punt23.authsmtp.com (8.14.2/8.14.2/) with ESMTP id tBJIgjeU092018
for <bitcoin-dev@lists.linuxfoundation.org>;
Sat, 19 Dec 2015 18:42:45 GMT
Received: from muck (S0106e091f5827ad2.ok.shawcable.net [24.71.232.17])
(authenticated bits=128)
by mail.authsmtp.com (8.14.2/8.14.2/) with ESMTP id tBJIgfHQ069562
(version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO)
for <bitcoin-dev@lists.linuxfoundation.org>;
Sat, 19 Dec 2015 18:42:44 GMT
Date: Sat, 19 Dec 2015 10:42:40 -0800
From: Peter Todd <pete@petertodd.org>
To: bitcoin-dev@lists.linuxfoundation.org
Message-ID: <20151219184240.GB12893@muck>
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha256;
protocol="application/pgp-signature"; boundary="8GpibOaaTibBMecb"
Content-Disposition: inline
X-Server-Quench: 4aca2f52-a680-11e5-bcde-0015176ca198
X-AuthReport-Spam: If SPAM / abuse - report it at:
http://www.authsmtp.com/abuse
X-AuthRoute: OCd2Yg0TA1ZNQRgX IjsJECJaVQIpKltL GxAVJwpGK10IU0Fd
P1hyKltILEZaQVBf Ri5dBBEKBAw1ADwr dVUTOktca1U6ClZ1
UkhIR0JTHA9sAxYF AlAcVgd1dhtEe3xu ZEF9W3hcQ0U0MTQH
OxkCbQwGY25lbmJR U0NRcU1QIVAbfElA aE0uUnsNfGQGM399
FQQ/MnVpZWwCcXsL SQhUfAIEfktDGDMx S1geGn0hHF1NWyU+
ZxYiLVUfVFkQLkUy Nl8tWFQXexYOFgRV HCkA
X-Authentic-SMTP: 61633532353630.1038:706
X-AuthFastPath: 0 (Was 255)
X-AuthSMTP-Origin: 24.71.232.17/587
X-AuthVirus-Status: No virus detected - but ensure you scan with your own
anti-virus system.
X-Spam-Status: No, score=-2.6 required=5.0 tests=BAYES_00,RCVD_IN_DNSWL_LOW
autolearn=ham version=3.3.1
X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on
smtp1.linux-foundation.org
Subject: [bitcoin-dev] We need to fix the block withholding attack
X-BeenThere: bitcoin-dev@lists.linuxfoundation.org
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: Bitcoin Development Discussion <bitcoin-dev.lists.linuxfoundation.org>
List-Unsubscribe: <https://lists.linuxfoundation.org/mailman/options/bitcoin-dev>,
<mailto:bitcoin-dev-request@lists.linuxfoundation.org?subject=unsubscribe>
List-Archive: <http://lists.linuxfoundation.org/pipermail/bitcoin-dev/>
List-Post: <mailto:bitcoin-dev@lists.linuxfoundation.org>
List-Help: <mailto:bitcoin-dev-request@lists.linuxfoundation.org?subject=help>
List-Subscribe: <https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev>,
<mailto:bitcoin-dev-request@lists.linuxfoundation.org?subject=subscribe>
X-List-Received-Date: Sat, 19 Dec 2015 18:42:47 -0000
--8GpibOaaTibBMecb
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable
At the recent Scaling Bitcoin conference in Hong Kong we had a chatham
house rules workshop session attending by representitives of a super
majority of the Bitcoin hashing power.
One of the issues raised by the pools present was block withholding
attacks, which they said are a real issue for them. In particular, pools
are receiving legitimate threats by bad actors threatening to use block
withholding attacks against them. Pools offering their services to the
general public without anti-privacy Know-Your-Customer have little
defense against such attacks, which in turn is a threat to the
decentralization of hashing power: without pools only fairly large
hashing power installations are profitable as variance is a very real
business expense. P2Pool is often brought up as a replacement for pools,
but it itself is still relatively vulnerable to block withholding, and
in any case has many other vulnerabilities and technical issues that has
prevented widespread adoption of P2Pool.
Fixing block withholding is relatively simple, but (so far) requires a
SPV-visible hardfork. (Luke-Jr's two-stage target mechanism) We should
do this hard-fork in conjunction with any blocksize increase, which will
have the desirable side effect of clearly show consent by the entire
ecosystem, SPV clients included.
Note that Ittay Eyal and Emin Gun Sirer have argued(1) that block
witholding attacks are a good thing, as in their model they can be used
by small pools against larger pools, disincentivising large pools.
However this argument is academic and not applicable to the real world,
as a much simpler defense against block withholding attacks is to use
anti-privacy KYC and the legal system combined with the variety of
withholding detection mechanisms only practical for large pools.
Equally, large hashing power installations - a dangerous thing for
decentralization - have no block withholding attack vulnerabilities.
1) http://hackingdistributed.com/2014/12/03/the-miners-dilemma/
--=20
'peter'[:-1]@petertodd.org
00000000000000000188b6321da7feae60d74c7b0becbdab3b1a0bd57f10947d
--8GpibOaaTibBMecb
Content-Type: application/pgp-signature; name="signature.asc"
Content-Description: Digital signature
-----BEGIN PGP SIGNATURE-----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==
=JwQ/
-----END PGP SIGNATURE-----
--8GpibOaaTibBMecb--
|
