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From: Peter R <peter_r@gmx.com>
In-Reply-To: <f4849cef-3c40-31a4-e323-6a731bb52bc2@cannon-ciota.info>
Date: Sat, 25 Mar 2017 13:28:44 -0700
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References: <5b9ba6c4-6d8f-9c0b-2420-2be6c30f87b5@cannon-ciota.info>
	<35ba77db-f95a-4517-c960-8ad42a633ba0@gmail.com>
	<f4849cef-3c40-31a4-e323-6a731bb52bc2@cannon-ciota.info>
To: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Defending against empty or near empty blocks from
	malicious miner takeover?
Precedence: list

One of the purported benefits of a soft-forking change (a tightening of =
the consensus rule set) is the reduced risk of a blockchain split =
compared to a loosening of the consensus rule set.  The way this works =
is that miners who fail to upgrade to the new tighter ruleset will have =
their non-compliant blocks orphaned by the hash power majority.  This is =
a strong incentive to upgrade and has historically worked well.  If a =
minority subset of the network didn=E2=80=99t want to abide by the new =
restricted rule set, a reasonable solution would be for them to change =
the proof-of-work and start a spin-off from the existing Bitcoin ledger =
(https://bitcointalk.org/index.php?topic=3D563972.0).

In the case of the coming network upgrade to larger blocks, a primary =
concern of both business such as Coinbase and Bitpay, and most miners, =
is the possibility of a blockchain split and the associated confusion, =
replay risk, etc.  By applying techniques that are known to be =
successful for soft-forking changes, we can likewise benefit in a way =
that makes a split less likely as we move towards larger blocks.  Two =
proposed techniques to reduce the chances of a split are:

1. That miners begin to orphan the blocks of non-upgraded miners once a =
super-majority of the network hash power has upgraded. This would serve =
as an expensive-to-ignore reminder to upgrade.

2. That, in the case where a minority branch emerges (unlikely IMO), =
majority miners would continually re-org that minority branch with empty =
blocks to prevent transactions from confirming, thereby eliminating =
replay risk.

Just like after a soft forking change, a minority that does not want to =
abide by the current ruleset enforced by the majority could change the =
proof-of-work and start a spin-off from the existing Bitcoin ledger, as =
suggested by Emin. =20

Best regards,
Peter R


> On Mar 25, 2017, at 9:12 AM, CANNON via bitcoin-dev =
<bitcoin-dev@lists.linuxfoundation.org> wrote:
>=20
> On 03/24/2017 07:00 PM, Aymeric Vitte wrote:
>> I don't know what "Time is running short I fear" stands for and when =
50%
>> is supposed to be reached
>=20
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA512
>=20
> On 03/24/2017 07:00 PM, Aymeric Vitte wrote: > I don't know what
> "Time is running short I fear" stands for and when 50% > is supposed
> to be reached
>=20
> According to current hashrate distribution tracking site coin.dance,
> very likely within less than four weeks according to current hashrate
> takeover rate.
>=20
> While a fork is very likely, that I dont really fear because worst
> case scenario is that bitcoin still survives and the invalid chain
> becomes an alt.  My fear is the centralized mining power being used
> to attack the valid chain with intentions on killing it. [1]
>=20
> Shouldn't this 50% attack they are threatening be a concern? If it
> is a concern, what options are on the table. If it is not a concern
> please enlightent me as to why.
>=20
>=20
> [1] Source:
> =
https://www.reddit.com/r/Bitcoin/comments/6172s3/peter_rizun_tells_miners_=
to_force_a_hard_fork_by/
>=20
> Text:
>=20
> The attack quoted from his article:
> =
https://medium.com/@peter_r/on-the-emerging-consensus-regarding-bitcoins-b=
lock-size-limit-insights-from-my-visit-with-2348878a16d8
>=20
>    [Level 2] Anti-split protection=E2=80=8A=E2=80=8AMiners will orphan =
the
>    blocks of non-compliant miners prior to the first larger block
>    to serve as a reminder to upgrade. Simply due to the possibility
>    of having blocks orphaned, all miners would be motivated to
>    begin signalling for larger blocks once support definitively
>    passes 51%. If some miners hold out (e.g., they may not be
>    paying attention regarding the upgrade), then they will begin
>    to pay attention after losing approximately $15,000 of revenue
>    due to an orphaned block.
>=20
>    [Level 3] Anti-split protection=E2=80=8A=E2=80=8AIn the scenario =
where Levels
>    1 and 2 protection fails to entice all non-compliant miners to
>    upgrade, a small-block minority chain may emerge. To address the
>    risk of coins being spent on this chain (replay risk), majority
>    miners will deploy hash power as needed to ensure the minority
>    chain includes only empty blocks after the forking point. This
>    can easily be accomplished if the majority miners maintain a
>    secret chain of empty blocks=E2=80=8A=E2=80=8Abuilt off their last =
empty
>    block=E2=80=8A=E2=80=8Apublishing only as much of this chain as =
necessary
>    to orphan any non-empty blocks produced on the minority chain.
>=20
>=20
>=20
>=20
> - --
> Cannon
> PGP Fingerprint: 2BB5 15CD 66E7 4E28 45DC 6494 A5A2 2879 3F06 E832=20
> Email: cannon@cannon-ciota.info
>=20
> NOTICE: ALL EMAIL CORRESPONDENCE NOT SIGNED/ENCRYPTED WITH PGP SHOULD=20=

> BE CONSIDERED POTENTIALLY FORGED, AND NOT PRIVATE.=20
> If this matters to you, use PGP.
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>=20
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