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
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
|
Received: from sog-mx-4.v43.ch3.sourceforge.com ([172.29.43.194]
helo=mx.sourceforge.net)
by sfs-ml-2.v29.ch3.sourceforge.com with esmtp (Exim 4.76)
(envelope-from <stanga@gmail.com>) id 1WhPU9-0002Ih-3l
for bitcoin-development@lists.sourceforge.net;
Mon, 05 May 2014 20:27:37 +0000
Received-SPF: pass (sog-mx-4.v43.ch3.sourceforge.com: domain of gmail.com
designates 209.85.215.48 as permitted sender)
client-ip=209.85.215.48; envelope-from=stanga@gmail.com;
helo=mail-la0-f48.google.com;
Received: from mail-la0-f48.google.com ([209.85.215.48])
by sog-mx-4.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128)
(Exim 4.76) id 1WhPU7-00034x-LM
for bitcoin-development@lists.sourceforge.net;
Mon, 05 May 2014 20:27:37 +0000
Received: by mail-la0-f48.google.com with SMTP id el20so3199639lab.7
for <bitcoin-development@lists.sourceforge.net>;
Mon, 05 May 2014 13:27:29 -0700 (PDT)
X-Received: by 10.152.20.137 with SMTP id n9mr3301455lae.39.1399321648899;
Mon, 05 May 2014 13:27:28 -0700 (PDT)
MIME-Version: 1.0
Sender: stanga@gmail.com
Received: by 10.112.46.203 with HTTP; Mon, 5 May 2014 13:27:08 -0700 (PDT)
In-Reply-To: <5367EA43.1090308@certimix.com>
References: <mailman.122233.1398039406.2207.bitcoin-development@lists.sourceforge.net>
<52CDA01B-13BF-4BB8-AC9A-5FBBB324FD15@sant.ox.ac.uk>
<20140423150555.GE19430@savin>
<CAOe4Ui=OaVLvh0vUnNv-1j41YB4B2x896DQ5b6xt4oUJ5oLPFg@mail.gmail.com>
<53638616.2030009@certimix.com> <536388F9.3040607@certimix.com>
<CAOe4UimBEe4t1Z41du3r8pQUOmzd_1V_aESizuiH2U6uvN9nFA@mail.gmail.com>
<5367EA43.1090308@certimix.com>
From: Ittay <ittay.eyal@cornell.edu>
Date: Mon, 5 May 2014 16:27:08 -0400
X-Google-Sender-Auth: nT0wjhzI6TpxQ9PiXStCeASjTR4
Message-ID: <CABT1wWkwLh8GVgE_0jgCJgm+rMwdKNMiVtSDQf28H8af0hci+w@mail.gmail.com>
To: Sergio Lerner <sergiolerner@certimix.com>
Content-Type: multipart/alternative; boundary=089e01493df6cf2daa04f8acf550
X-Spam-Score: -0.5 (/)
X-Spam-Report: Spam Filtering performed by mx.sourceforge.net.
See http://spamassassin.org/tag/ for more details.
-1.5 SPF_CHECK_PASS SPF reports sender host as permitted sender for
sender-domain
0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider
(stanga[at]gmail.com)
-0.0 SPF_PASS SPF: sender matches SPF record
1.0 HTML_MESSAGE BODY: HTML included in message
0.1 DKIM_SIGNED Message has a DKIM or DK signature,
not necessarily valid
-0.1 DKIM_VALID Message has at least one valid DKIM or DK signature
X-Headers-End: 1WhPU7-00034x-LM
Cc: bitcoin-research@lists.cs.princeton.edu,
"bitcoin-development@lists.sourceforge.net"
<bitcoin-development@lists.sourceforge.net>,
Joseph Bonneau <jbonneau@princeton.edu>,
=?UTF-8?Q?Emin_G=C3=BCn_Sirer?= <egs@systems.cs.cornell.edu>,
Ittay Eyal <ittay.eyal@cornell.edu>
Subject: Re: [Bitcoin-development] Block collision resolution using the
DECOR protocol and Bonneau's Kickbacks problem
X-BeenThere: bitcoin-development@lists.sourceforge.net
X-Mailman-Version: 2.1.9
Precedence: list
List-Id: <bitcoin-development.lists.sourceforge.net>
List-Unsubscribe: <https://lists.sourceforge.net/lists/listinfo/bitcoin-development>,
<mailto:bitcoin-development-request@lists.sourceforge.net?subject=unsubscribe>
List-Archive: <http://sourceforge.net/mailarchive/forum.php?forum_name=bitcoin-development>
List-Post: <mailto:bitcoin-development@lists.sourceforge.net>
List-Help: <mailto:bitcoin-development-request@lists.sourceforge.net?subject=help>
List-Subscribe: <https://lists.sourceforge.net/lists/listinfo/bitcoin-development>,
<mailto:bitcoin-development-request@lists.sourceforge.net?subject=subscribe>
X-List-Received-Date: Mon, 05 May 2014 20:27:37 -0000
--089e01493df6cf2daa04f8acf550
Content-Type: text/plain; charset=UTF-8
As far as I understand, the incentives Sergio suggests would work. So
we can assume that the pruned uncle blocks would still win their creators
at least partial revenue.
As for selfish mining - I'm not sure how GHOST affects it. I don't think it
does. The selfish miners just care about heaviest subtree rather than
longest chain. DECOR changes revenue collection significantly, so it
certainly affects selfish mining. I believe it changes the threshold at
which
selfish mining is profitable, but doesn't deter selfish mining completely:
Selfish miners can still cause others to reduce their revenue by having
them work on older blocks.
Ittay
On Mon, May 5, 2014 at 3:45 PM, Sergio Lerner <sergiolerner@certimix.com>wrote:
>
> On 02/05/2014 10:56 a.m., Joseph Bonneau wrote:
> > This is an interesting idea Sergio. I have two concerns:
> >
> > You mention "50% of the block reward" going to the uncle block. Does
> > this mean the parent gets 1, and the uncle 0.5, or both get 0.5? In
> > the first interpretation (which I assumed was the design), mining is
> > no longer a zero-sum game and this could have lots of unforeseen
> > implications. For example, selfish mining might be more profitable,
> > since you're less disincentivized to avoid conflicts.
> The second interpretation is the correct one.
> > In the second interpretation, there's pressure to have the next miner
> > ignore the uncle to not share the reward. This would encourage
> > kickback-style attacks and advantage large mining pools because they
> > can mine on their own blocks and ignore colliding uncles.
> Including an uncle can be done at any time before a coinbase matures
> (100 blocks) (of course the term "uncle" is misleading in those cases) .
> So, for example, the uncle can be included 50 blocks afterward. So it's
> very difficult that a miner prevents other miners from including the
> uncle and taking the reward given by uncle inclusion.
>
> Same ineffective attack:
> A big miner could try to bribe all other miners not to include the
> uncle, but this would be terribly costly. Suppose that I mine a block
> ignoring an uncle Z and then I publish this message: "Every miner from
> block number X to block number Y that does not include this uncle Z will
> be given Q Bitcoins". How much would Q be? Since by including the uncle
> the miner gets 5 BTC of reward (in the example case where block reward
> is 50 BTC), then each bribery payment would have to be higher than 5
> BTC, totaling 500 BTC ! much more than the 25 BTC the miner will loose
> by including the uncle.
>
> Just by sending a transaction with a lot of fees that depends on my
> block does not prevent subsequent miners from including the supposedly
> banned uncle.
>
> Then, I think there are no kickback-style attacks.
>
> >
> > Also, I think this came up in the Princeton meet-up, but it's not
> > ideal to just hash the blocks to decide the "winner" because this lets
> > you know in advance your block's likelihood of winning a collision by
> > looking at how high or low its hash is, in which case you can publish
> > a weak block right away or withhold a strong one and do selfish
> > mining. A better approach to break ties between blocks A and B is to
> > see if H(A||B) < H(B||A). That way neither block holder can find out
> > in advance if their block is likely to win a collision.
> >
> In the DECOR protocol, I think selfish miners cannot get any advantage,
> because the blocks that loose the latency race will come back as uncles
> and get their reward share anyway. Maybe Ittay Eyal and Emin Gun Sirer
> can say more about this...
>
> Best regards, Sergio.
>
--089e01493df6cf2daa04f8acf550
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
<div dir=3D"ltr">As far as I understand, the incentives Sergio suggests wou=
ld work. So=C2=A0<div>we can assume that the pruned uncle blocks would stil=
l win their creators=C2=A0</div><div>at least partial revenue.=C2=A0</div><=
div><br></div>
<div>As for selfish mining - I'm not sure how GHOST affects it. I don&#=
39;t think it=C2=A0</div><div>does. The selfish miners just care about heav=
iest subtree rather than=C2=A0</div><div>longest chain. DECOR changes reven=
ue collection significantly, so it=C2=A0</div>
<div>certainly affects selfish mining. I believe it changes the threshold a=
t which=C2=A0</div><div>selfish mining is profitable, but doesn't deter=
selfish mining completely:=C2=A0</div><div>Selfish miners can still cause =
others to reduce their revenue by having=C2=A0</div>
<div>them work on older blocks.=C2=A0</div><div><br></div><div>Ittay=C2=A0<=
/div><div><br></div></div><div class=3D"gmail_extra"><br><br><div class=3D"=
gmail_quote">On Mon, May 5, 2014 at 3:45 PM, Sergio Lerner <span dir=3D"ltr=
"><<a href=3D"mailto:sergiolerner@certimix.com" target=3D"_blank">sergio=
lerner@certimix.com</a>></span> wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex"><div class=3D""><br>
On 02/05/2014 10:56 a.m., Joseph Bonneau wrote:<br>
> This is an interesting idea Sergio. I have two concerns:<br>
><br>
> You mention "50% of the block reward" going to the uncle blo=
ck. Does<br>
> this mean the parent gets 1, and the uncle 0.5, or both get 0.5? In<br=
>
> the first interpretation (which I assumed was the design), mining is<b=
r>
> no longer a zero-sum game and this could have lots of unforeseen<br>
> implications. For example, selfish mining might be more profitable,<br=
>
> since you're less disincentivized to avoid conflicts.<br>
</div>The second interpretation is the correct one.<br>
<div class=3D"">> In the second interpretation, there's pressure to =
have the next miner<br>
> ignore the uncle to not share the reward. This would encourage<br>
> kickback-style attacks and advantage large mining pools because they<b=
r>
> can mine on their own blocks and ignore colliding uncles.<br>
</div>Including an uncle can be done at any time before a coinbase matures<=
br>
(100 blocks) (of course the term "uncle" is misleading in those c=
ases) .<br>
So, for example, the uncle can be included 50 blocks afterward. So it's=
<br>
very difficult that a miner prevents other miners from including the<br>
uncle and taking the reward given by uncle inclusion.<br>
<br>
Same ineffective attack:<br>
A big miner could try to bribe all other miners not to include the<br>
uncle, but this would be terribly costly. Suppose that I mine a block<br>
ignoring an uncle Z and then I publish this message: "Every miner from=
<br>
block number X to block number Y that does not include this uncle Z will<br=
>
be given Q Bitcoins". How much would Q be? Since by including the uncl=
e<br>
the miner gets 5 BTC of reward (in the example case where block reward<br>
is 50 BTC), then each bribery payment would have to be higher than 5<br>
BTC, totaling 500 BTC ! much more than the 25 BTC the miner will loose<br>
by including the uncle.<br>
<br>
Just by sending a transaction with a lot of fees that depends on my<br>
block does not prevent subsequent miners from including the supposedly<br>
banned uncle.<br>
<br>
Then, I think there are no kickback-style attacks.<br>
<div class=3D""><br>
><br>
> Also, I think this came up in the Princeton meet-up, but it's not<=
br>
> ideal to just hash the blocks to decide the "winner" because=
this lets<br>
> you know in advance your block's likelihood of winning a collision=
by<br>
> looking at how high or low its hash is, in which case you can publish<=
br>
> a weak block right away or withhold a strong one and do selfish<br>
> mining. A better approach to break ties between blocks A and B is to<b=
r>
> see if H(A||B) < H(B||A). That way neither block holder can find ou=
t<br>
> in advance if their block is likely to win a collision.<br>
><br>
</div>In the DECOR protocol, I think selfish miners cannot get any advantag=
e,<br>
because the blocks that loose the latency race will come back as uncles<br>
and get their reward share anyway. Maybe Ittay Eyal and Emin Gun Sirer<br>
can say more about this...<br>
<br>
Best regards, Sergio.<br>
</blockquote></div><br></div>
--089e01493df6cf2daa04f8acf550--
|
