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[49.127.13.214]) by smtp.gmail.com with ESMTPSA id a2sm26091835pfg.90.2019.12.08.16.45.30 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 08 Dec 2019 16:45:31 -0800 (PST) From: Runchao Han Message-Id: <29C07E1A-DC6B-49F0-893B-A59E7BD8DB1C@monash.edu> Content-Type: multipart/alternative; boundary="Apple-Mail=_83A96B04-E5BD-42EE-8DF6-3D3076A186B7" Mime-Version: 1.0 (Mac OS X Mail 13.0 \(3601.0.4\)) Date: Mon, 9 Dec 2019 11:45:27 +1100 In-Reply-To: To: Cheng Wang References: X-Mailer: Apple Mail (2.3601.0.4) X-Mailman-Approved-At: Mon, 09 Dec 2019 05:36:26 +0000 Cc: bitcoin-dev@lists.linuxfoundation.org Subject: Re: [bitcoin-dev] Reducing energy consumption and increasing security at the same time X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Bitcoin Protocol Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 09 Dec 2019 02:30:15 -0000 --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 > To: bitcoin-dev@lists.linuxfoundation.org > Subject: [bitcoin-dev] Reducing energy consumption and increasing > security at the same time > Message-ID: > = > 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
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.gmai= l.com>
Content-Type: text/plain; charset=3D"utf-8"
Hi Everyone,

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.

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.

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.

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.

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.

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
It's inspired by the recent great paper of = Itay, Alexander, and Ittay:
https://arxiv.org/abs/1911.04124

Best,
Cheng Wang

= --Apple-Mail=_83A96B04-E5BD-42EE-8DF6-3D3076A186B7--