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authorRunchao Han <runchao.han@monash.edu>2019-12-09 11:45:27 +1100
committerbitcoindev <bitcoindev@gnusha.org>2019-12-09 02:30:15 +0000
commitd58e1f5ab49c5d52758d5eb66e228bd51589a032 (patch)
tree17192a5266d15fe854ccf53efc7da3067d241640
parent3c4c917d2f740817b7abeeba26e4d3408eac2687 (diff)
downloadpi-bitcoindev-d58e1f5ab49c5d52758d5eb66e228bd51589a032.tar.gz
pi-bitcoindev-d58e1f5ab49c5d52758d5eb66e228bd51589a032.zip
Re: [bitcoin-dev] Reducing energy consumption and increasing security at the same time
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+From: Runchao Han <runchao.han@monash.edu>
+Message-Id: <29C07E1A-DC6B-49F0-893B-A59E7BD8DB1C@monash.edu>
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+Date: Mon, 9 Dec 2019 11:45:27 +1100
+In-Reply-To: <mailman.3482.1575825776.25512.bitcoin-dev@lists.linuxfoundation.org>
+To: Cheng Wang <cheng@alephium.org>
+References: <mailman.3482.1575825776.25512.bitcoin-dev@lists.linuxfoundation.org>
+X-Mailer: Apple Mail (2.3601.0.4)
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+Cc: bitcoin-dev@lists.linuxfoundation.org
+Subject: Re: [bitcoin-dev] Reducing energy consumption and increasing
+ security at the same time
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+
+--Apple-Mail=_83A96B04-E5BD-42EE-8DF6-3D3076A186B7
+Content-Transfer-Encoding: quoted-printable
+Content-Type: text/plain;
+ charset=us-ascii
+
+Hi Cheng,
+
+This is an interesting proposal!
+While the incentive analysis is sound, I have two concerns:
+
+## What if a guy keeps mining easy blocks to launch 51% attacks?
+
+With PoLW, a miner can sacrifice the coinbase reward as much as possible =
+to mine blocks faster.
+If the blockchain follows the longest chain rule, PoLW may make 51% =
+attacks much easier.
+An easy way of fixing this is to choose the chain with most work rather =
+than most blocks.
+
+## What if the coinbase tx is no longer the majority of mining reward, =
+but the fx fee?
+
+This might happen in the future.
+A possible solution is to limit the number of txs for easy blocks.
+For example, if a miner chooses to mine blocks N times easier, he can =
+only include txs of which the total size is <=3D (block_size - =
+metadata_size) / N.
+
+Best regards,
+Runchao
+
+> Date: Sun, 8 Dec 2019 11:43:49 +0100
+> From: Cheng Wang <cheng@alephium.org>
+> To: bitcoin-dev@lists.linuxfoundation.org
+> Subject: [bitcoin-dev] Reducing energy consumption and increasing
+> security at the same time
+> Message-ID:
+> =
+<CAJgZxF4G_BjJ=3DOhuzhjfZtkePnEc2hz8DMZzFzWKBNh17XhBeQ@mail.gmail.com>
+> Content-Type: text/plain; charset=3D"utf-8"
+>=20
+> Hi Everyone,
+>=20
+> I would like to share my serious work on reducing the energy =
+consumption of
+> PoW without sacrificing security. My new type of algorithm is called =
+PoLW.
+> For a practical system where mining is profitable, PoLW could actually
+> improve the security of the system.
+>=20
+> The idea is to shift part of the external cost of mining in the =
+physical
+> world (mainly energy consumption) to the internal cost of the network. =
+In
+> PoLW, the miners are able to give up part of the coinbase reward so as =
+to
+> get weight (> 1) for the block hash they produce. The total cost of
+> generating a new block would still be equal to maximal coinbase reward =
+in
+> equilibrium.
+>=20
+> I analyzed two algorithms in the paper: linear PoLW and exponential =
+PoLW.
+> Linear PoLW could reduce energy consumption by a factor close to 1/2 =
+in
+> equilibrium, while exponential PoLW could reduce energy consumption by =
+an
+> arbitrary factor in equilibrium.
+>=20
+> In a practical system, mining is usually (if not always) profitable. =
+If we
+> transition from PoW to PoLW, the external costs of mining would =
+decrease
+> and the internal costs will increase. However, the decrease in =
+external
+> costs would be less than the increase in internal costs since mining =
+is
+> profitable. The total cost of block generation would get higher, =
+therefore,
+> the security will increase.
+>=20
+> Of course, we could not decrease the external costs of any existing =
+system
+> by a factor close to zero immediately. There is a section in my paper
+> discussing this particularly. The principle of applying PoLW is that
+> keeping the absolute external cost increasing all the time, but the
+> percentage of external cost in the total cost gets lower eventually.
+>=20
+> This work is based on solid math calculation, and I am looking forward =
+to
+> feedback and discussions. My paper is available at:
+> https://github.com/alephium/research/raw/master/polw.pdf
+>=20
+> It's inspired by the recent great paper of Itay, Alexander, and Ittay:
+> https://arxiv.org/abs/1911.04124
+>=20
+> Best,
+> Cheng Wang
+
+
+--Apple-Mail=_83A96B04-E5BD-42EE-8DF6-3D3076A186B7
+Content-Transfer-Encoding: quoted-printable
+Content-Type: text/html;
+ charset=us-ascii
+
+<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; line-break: after-white-space;" class=3D""><div =
+class=3D"">Hi Cheng,</div><div class=3D""><br class=3D""></div>This is =
+an interesting proposal!<div class=3D"">While the incentive analysis is =
+sound, I have two concerns:</div><div class=3D""><br class=3D""></div><div=
+ class=3D"">##&nbsp;<span style=3D"font-family: &quot;Helvetica =
+Neue&quot;; font-size: 13px;" class=3D"">What if a guy keeps mining easy =
+blocks to launch 51% attacks?</span></div><div class=3D""><span =
+style=3D"font-family: &quot;Helvetica Neue&quot;; font-size: 13px;" =
+class=3D""><br class=3D""></span></div><div class=3D""><font =
+face=3D"Helvetica Neue" size=3D"2" class=3D"">With PoLW, a miner can =
+sacrifice the coinbase reward as much as possible to mine blocks =
+faster.</font></div><div class=3D""><font face=3D"Helvetica Neue" =
+size=3D"2" class=3D"">If the blockchain follows the&nbsp;longest chain =
+rule, PoLW may make 51%&nbsp;attacks much easier.</font></div><div =
+class=3D""><font face=3D"Helvetica Neue" size=3D"2" class=3D"">An easy =
+way of fixing this is to choose the chain with most work rather than =
+most blocks.</font></div><div class=3D""><br class=3D""></div><div =
+class=3D"">## What if the coinbase tx is no longer the majority of =
+mining reward, but the fx fee?</div><div class=3D""><br =
+class=3D""></div><div class=3D"">This might happen in the =
+future.</div><div class=3D"">A possible solution is to limit the number =
+of txs for easy blocks.</div><div class=3D"">For example, if a miner =
+chooses to mine blocks N times easier, he can only include txs of which =
+the total size is &lt;=3D (block_size - metadata_size) / N.</div><div =
+class=3D""><br class=3D""></div><div class=3D"">Best regards,</div><div =
+class=3D"">Runchao</div><div class=3D""><br class=3D""></div><div =
+class=3D""><div><blockquote type=3D"cite" class=3D""><div class=3D""><div =
+class=3D"">Date: Sun, 8 Dec 2019 11:43:49 +0100<br class=3D"">From: =
+Cheng Wang &lt;<a href=3D"mailto:cheng@alephium.org" =
+class=3D"">cheng@alephium.org</a>&gt;<br class=3D"">To: <a =
+href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" =
+class=3D"">bitcoin-dev@lists.linuxfoundation.org</a><br =
+class=3D"">Subject: [bitcoin-dev] Reducing energy consumption and =
+increasing<br class=3D""><span class=3D"Apple-tab-span" =
+style=3D"white-space:pre"> </span>security<span =
+class=3D"Apple-tab-span" style=3D"white-space:pre"> </span>at the =
+same time<br class=3D"">Message-ID:<br class=3D""><span =
+class=3D"Apple-tab-span" style=3D"white-space:pre"> </span>&lt;<a =
+href=3D"mailto:CAJgZxF4G_BjJ=3DOhuzhjfZtkePnEc2hz8DMZzFzWKBNh17XhBeQ@mail.=
+gmail.com" =
+class=3D"">CAJgZxF4G_BjJ=3DOhuzhjfZtkePnEc2hz8DMZzFzWKBNh17XhBeQ@mail.gmai=
+l.com</a>&gt;<br class=3D"">Content-Type: text/plain; charset=3D"utf-8"<br=
+ class=3D""><br class=3D"">Hi Everyone,<br class=3D""><br class=3D"">I =
+would like to share my serious work on reducing the energy consumption =
+of<br class=3D"">PoW without sacrificing security. My new type of =
+algorithm is called PoLW.<br class=3D"">For a practical system where =
+mining is profitable, PoLW could actually<br class=3D"">improve the =
+security of the system.<br class=3D""><br class=3D"">The idea is to =
+shift part of the external cost of mining in the physical<br =
+class=3D"">world (mainly energy consumption) to the internal cost of the =
+network. In<br class=3D"">PoLW, the miners are able to give up part of =
+the coinbase reward so as to<br class=3D"">get weight (&gt; 1) for the =
+block hash they produce. The total cost of<br class=3D"">generating a =
+new block would still be equal to maximal coinbase reward in<br =
+class=3D"">equilibrium.<br class=3D""><br class=3D"">I analyzed two =
+algorithms in the paper: linear PoLW and exponential PoLW.<br =
+class=3D"">Linear PoLW could reduce energy consumption by a factor close =
+to 1/2 in<br class=3D"">equilibrium, while exponential PoLW could reduce =
+energy consumption by an<br class=3D"">arbitrary factor in =
+equilibrium.<br class=3D""><br class=3D"">In a practical system, mining =
+is usually (if not always) profitable. If we<br class=3D"">transition =
+from PoW to PoLW, the external costs of mining would decrease<br =
+class=3D"">and the internal costs will increase. However, the decrease =
+in external<br class=3D"">costs would be less than the increase in =
+internal costs since mining is<br class=3D"">profitable. The total cost =
+of block generation would get higher, therefore,<br class=3D"">the =
+security will increase.<br class=3D""><br class=3D"">Of course, we could =
+not decrease the external costs of any existing system<br class=3D"">by =
+a factor close to zero immediately. There is a section in my paper<br =
+class=3D"">discussing this particularly. The principle of applying PoLW =
+is that<br class=3D"">keeping the absolute external cost increasing all =
+the time, but the<br class=3D"">percentage of external cost in the total =
+cost gets lower eventually.<br class=3D""><br class=3D"">This work is =
+based on solid math calculation, and I am looking forward to<br =
+class=3D"">feedback and discussions. My paper is available at:<br =
+class=3D""><a =
+href=3D"https://github.com/alephium/research/raw/master/polw.pdf" =
+class=3D"">https://github.com/alephium/research/raw/master/polw.pdf</a><br=
+ class=3D""><br class=3D"">It's inspired by the recent great paper of =
+Itay, Alexander, and Ittay:<br =
+class=3D"">https://arxiv.org/abs/1911.04124<br class=3D""><br =
+class=3D"">Best,<br class=3D"">Cheng Wang<br =
+class=3D""></div></div></blockquote></div><br =
+class=3D""></div></body></html>=
+
+--Apple-Mail=_83A96B04-E5BD-42EE-8DF6-3D3076A186B7--
+