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Date: Thu, 10 Dec 2015 05:16:00 +0800
Message-ID: <CAJmQggBfYyk3cPAL57NZ3ecPG_ZxffjPftc0-EkTzKagjodgNQ@mail.gmail.com>
From: Loi Luu <loi.luuthe@gmail.com>
To: Akiva Lichtner <akiva.lichtner@gmail.com>
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Subject: Re: [bitcoin-dev] Scaling by Partitioning
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I guess the most basic question is how do you define a coin here?

Thanks,
Loi Luu
On 10 Dec 2015 2:26 a.m., "Akiva Lichtner" <akiva.lichtner@gmail.com> wrote:

> Thanks for giving serious consideration to my post.
>
> With regard to your question "if a transaction spends a "coin" that
> ends in "1" and creates a new coin that ends in "1", which partition
> should process the transaction?", I would answer that only one
> partition is involved. In other words, there are N independent block
> chains that never cross paths.
>
> With regard to your question "what is the prior data needed to
> validate that kind of TXs?" I do not understand what this means. If
> you can dumb it down a bit that would be good because there could be
> some interesting concern in this question.
>
> Since partitions are completely segregated, there is no need for a
> node to work on multiple partitions simultaneously. For attacks to be
> defeated a node needs to be able to work on multiple partitions in
> turn, not at the same time. The reason is because if the computing
> power of the good-faith nodes is unbalanced this gives attackers an
> unfair advantage.
>
> On 12/9/15, Loi Luu via bitcoin-dev
> <bitcoin-dev@lists.linuxfoundation.org> wrote:
> > Dear Akiva,
> >
> > Its Loi Luu, one of the authors of the SCP protocol (
> > http://eprint.iacr.org/2015/1168.pdf ).
> >
> > Before SCP, we had been thinking hard about how to do sharding
> efficiently
> > without degrading any security guarantee. A simple solution which splits
> > the coins, or TXs in to several partitions will just not work. You have
> to
> > answer more questions to have a good solutions. For example, I wonder in
> > your proposal, if a transaction spends a "coin" that ends in "1" and
> > creates a new coin that ends in "1", which partition should process the
> > transaction? What is the prior data needed to validate that kind of TXs?
> >
> > The problem with other proposals, and probably yours as well,  that we
> see
> > is that the amount of data that you need to broadcast immediately to the
> > network increases linearly with the number of TXs that the network can
> > process. Thus, sharding does not bring any advantage than simply using
> > other techniques to publish more blocks in one epoch (like Bitcoin-NG,
> > Ghost). The whole point of using sharding/ partition is to localize
> > the bandwidth used, and only broadcast only a minimal data to the
> network.
> >
> > Clearly we are able to localize the bandwidth used with our SCP protocol.
> > The cost is that now recipients need to  themselves verify whether a
> > transaction is double spending. However, we think that it is a reasonable
> > tradeoff, given the potential scalability that SCP can provides.
> >
> > Thanks,
> > Loi Luu.
> >
> > On Wed, Dec 9, 2015 at 12:27 AM, Akiva Lichtner via bitcoin-dev <
> > bitcoin-dev@lists.linuxfoundation.org> wrote:
> >
> >> Hello,
> >>
> >> I am seeking some expert feedback on an idea for scaling Bitcoin. As a
> >> brief introduction: I work in the payment industry and I have twenty
> >> years'
> >> experience in development. I have some experience with process groups
> and
> >> ordering protocols too. I think I understand Satoshi's paper but I admit
> >> I
> >> have not read the source code.
> >>
> >> The idea is to run more than one simultaneous chain, each chain
> defeating
> >> double spending on only part of the coin. The coin would be partitioned
> >> by
> >> radix (or modulus, not sure what to call it.) For example in order to
> >> multiply throughput by a factor of ten you could run ten parallel
> chains,
> >> one would work on coin that ends in "0", one on coin that ends in "1",
> >> and
> >> so on up to "9".
> >>
> >> The number of chains could increase automatically over time based on the
> >> moving average of transaction volume.
> >>
> >> Blocks would have to contain the number of the partition they belong to,
> >> and miners would have to round-robin through partitions so that an
> >> attacker
> >> would not have an unfair advantage working on just one partition.
> >>
> >> I don't think there is much impact to miners, but clients would have to
> >> send more than one message in order to spend money. Client messages will
> >> need to enumerate coin using some sort of compression, to save space.
> >> This
> >> seems okay to me since often in computing client software does have to
> >> break things up in equal parts (e.g. memory pages, file system blocks,)
> >> and
> >> the client software could hide the details.
> >>
> >> Best wishes for continued success to the project.
> >>
> >> Regards,
> >> Akiva
> >>
> >> P.S. I found a funny anagram for SATOSHI NAKAMOTO: "NSA IS OOOK AT MATH"
> >>
> >>
> >> _______________________________________________
> >> bitcoin-dev mailing list
> >> bitcoin-dev@lists.linuxfoundation.org
> >> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
> >>
> >>
> >
>

--001a1142789ed8c55d05267d98a6
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: quoted-printable

<p dir=3D"ltr">I guess the most basic question is how do you define a coin =
here?</p>
<p dir=3D"ltr">Thanks,<br>
Loi Luu</p>
<div class=3D"gmail_quote">On 10 Dec 2015 2:26 a.m., &quot;Akiva Lichtner&q=
uot; &lt;<a href=3D"mailto:akiva.lichtner@gmail.com">akiva.lichtner@gmail.c=
om</a>&gt; wrote:<br type=3D"attribution"><blockquote class=3D"gmail_quote"=
 style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Th=
anks for giving serious consideration to my post.<br>
<br>
With regard to your question &quot;if a transaction spends a &quot;coin&quo=
t; that<br>
ends in &quot;1&quot; and creates a new coin that ends in &quot;1&quot;, wh=
ich partition<br>
should process the transaction?&quot;, I would answer that only one<br>
partition is involved. In other words, there are N independent block<br>
chains that never cross paths.<br>
<br>
With regard to your question &quot;what is the prior data needed to<br>
validate that kind of TXs?&quot; I do not understand what this means. If<br=
>
you can dumb it down a bit that would be good because there could be<br>
some interesting concern in this question.<br>
<br>
Since partitions are completely segregated, there is no need for a<br>
node to work on multiple partitions simultaneously. For attacks to be<br>
defeated a node needs to be able to work on multiple partitions in<br>
turn, not at the same time. The reason is because if the computing<br>
power of the good-faith nodes is unbalanced this gives attackers an<br>
unfair advantage.<br>
<br>
On 12/9/15, Loi Luu via bitcoin-dev<br>
&lt;<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org">bitcoin-dev@li=
sts.linuxfoundation.org</a>&gt; wrote:<br>
&gt; Dear Akiva,<br>
&gt;<br>
&gt; Its Loi Luu, one of the authors of the SCP protocol (<br>
&gt; <a href=3D"http://eprint.iacr.org/2015/1168.pdf" rel=3D"noreferrer" ta=
rget=3D"_blank">http://eprint.iacr.org/2015/1168.pdf</a> ).<br>
&gt;<br>
&gt; Before SCP, we had been thinking hard about how to do sharding efficie=
ntly<br>
&gt; without degrading any security guarantee. A simple solution which spli=
ts<br>
&gt; the coins, or TXs in to several partitions will just not work. You hav=
e to<br>
&gt; answer more questions to have a good solutions. For example, I wonder =
in<br>
&gt; your proposal, if a transaction spends a &quot;coin&quot; that ends in=
 &quot;1&quot; and<br>
&gt; creates a new coin that ends in &quot;1&quot;, which partition should =
process the<br>
&gt; transaction? What is the prior data needed to validate that kind of TX=
s?<br>
&gt;<br>
&gt; The problem with other proposals, and probably yours as well,=C2=A0 th=
at we see<br>
&gt; is that the amount of data that you need to broadcast immediately to t=
he<br>
&gt; network increases linearly with the number of TXs that the network can=
<br>
&gt; process. Thus, sharding does not bring any advantage than simply using=
<br>
&gt; other techniques to publish more blocks in one epoch (like Bitcoin-NG,=
<br>
&gt; Ghost). The whole point of using sharding/ partition is to localize<br=
>
&gt; the bandwidth used, and only broadcast only a minimal data to the netw=
ork.<br>
&gt;<br>
&gt; Clearly we are able to localize the bandwidth used with our SCP protoc=
ol.<br>
&gt; The cost is that now recipients need to=C2=A0 themselves verify whethe=
r a<br>
&gt; transaction is double spending. However, we think that it is a reasona=
ble<br>
&gt; tradeoff, given the potential scalability that SCP can provides.<br>
&gt;<br>
&gt; Thanks,<br>
&gt; Loi Luu.<br>
&gt;<br>
&gt; On Wed, Dec 9, 2015 at 12:27 AM, Akiva Lichtner via bitcoin-dev &lt;<b=
r>
&gt; <a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org">bitcoin-dev@l=
ists.linuxfoundation.org</a>&gt; wrote:<br>
&gt;<br>
&gt;&gt; Hello,<br>
&gt;&gt;<br>
&gt;&gt; I am seeking some expert feedback on an idea for scaling Bitcoin. =
As a<br>
&gt;&gt; brief introduction: I work in the payment industry and I have twen=
ty<br>
&gt;&gt; years&#39;<br>
&gt;&gt; experience in development. I have some experience with process gro=
ups and<br>
&gt;&gt; ordering protocols too. I think I understand Satoshi&#39;s paper b=
ut I admit<br>
&gt;&gt; I<br>
&gt;&gt; have not read the source code.<br>
&gt;&gt;<br>
&gt;&gt; The idea is to run more than one simultaneous chain, each chain de=
feating<br>
&gt;&gt; double spending on only part of the coin. The coin would be partit=
ioned<br>
&gt;&gt; by<br>
&gt;&gt; radix (or modulus, not sure what to call it.) For example in order=
 to<br>
&gt;&gt; multiply throughput by a factor of ten you could run ten parallel =
chains,<br>
&gt;&gt; one would work on coin that ends in &quot;0&quot;, one on coin tha=
t ends in &quot;1&quot;,<br>
&gt;&gt; and<br>
&gt;&gt; so on up to &quot;9&quot;.<br>
&gt;&gt;<br>
&gt;&gt; The number of chains could increase automatically over time based =
on the<br>
&gt;&gt; moving average of transaction volume.<br>
&gt;&gt;<br>
&gt;&gt; Blocks would have to contain the number of the partition they belo=
ng to,<br>
&gt;&gt; and miners would have to round-robin through partitions so that an=
<br>
&gt;&gt; attacker<br>
&gt;&gt; would not have an unfair advantage working on just one partition.<=
br>
&gt;&gt;<br>
&gt;&gt; I don&#39;t think there is much impact to miners, but clients woul=
d have to<br>
&gt;&gt; send more than one message in order to spend money. Client message=
s will<br>
&gt;&gt; need to enumerate coin using some sort of compression, to save spa=
ce.<br>
&gt;&gt; This<br>
&gt;&gt; seems okay to me since often in computing client software does hav=
e to<br>
&gt;&gt; break things up in equal parts (e.g. memory pages, file system blo=
cks,)<br>
&gt;&gt; and<br>
&gt;&gt; the client software could hide the details.<br>
&gt;&gt;<br>
&gt;&gt; Best wishes for continued success to the project.<br>
&gt;&gt;<br>
&gt;&gt; Regards,<br>
&gt;&gt; Akiva<br>
&gt;&gt;<br>
&gt;&gt; P.S. I found a funny anagram for SATOSHI NAKAMOTO: &quot;NSA IS OO=
OK AT MATH&quot;<br>
&gt;&gt;<br>
&gt;&gt;<br>
&gt;&gt; _______________________________________________<br>
&gt;&gt; bitcoin-dev mailing list<br>
&gt;&gt; <a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org">bitcoin-d=
ev@lists.linuxfoundation.org</a><br>
&gt;&gt; <a href=3D"https://lists.linuxfoundation.org/mailman/listinfo/bitc=
oin-dev" rel=3D"noreferrer" target=3D"_blank">https://lists.linuxfoundation=
.org/mailman/listinfo/bitcoin-dev</a><br>
&gt;&gt;<br>
&gt;&gt;<br>
&gt;<br>
</blockquote></div>

--001a1142789ed8c55d05267d98a6--