Re: [bitcoin-dev] Is it possible for there to be two chains after a hard fork?

From: Mark Friedenbach <mark@friedenbach•org>
To: "Jonathan Toomim (Toomim Bros)" <j@toom•im>
Cc: Bitcoin Dev <bitcoin-dev@lists•linuxfoundation.org>
Subject: Re: [bitcoin-dev] Is it possible for there to be two chains after a hard fork?
Date: Tue, 29 Sep 2015 07:59:46 -0700	[thread overview]
Message-ID: <CAOG=w-tdUx_ms=V5L4Zv35b5DdPkdHQLw=B0c4uoOtZw2jS+Hw@mail.gmail.com> (raw)
In-Reply-To: <0DCA91F5-E6D3-49CB-B473-D1AE1D3D9885@toom.im>

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You don't need to appeal to human psychology. At 75% threshold, it takes
only 25.01% of the hashpower to report but not actually enforce the fork to
cause the majority hashpower to remain on the old chain, but for upgraded
clients to start rejecting the old chain. With 95% the same problem exists
but with a threshold of 45.01%. BIP 66 showed this not to be a hypothetical
concern.

On Tue, Sep 29, 2015 at 7:17 AM, Jonathan Toomim (Toomim Bros) via
bitcoin-dev <bitcoin-dev@lists•linuxfoundation.org> wrote:

> At the 95% threshold, I don't think it would happen unless there was a
> very strong motivating factor, like a small group believing that CLTV was a
> conspiracy run by the NSA agent John Titor to contaminate our precious
> bodily fluids with time-traveling traveler's cheques.
>
> At the 75% threshold, I think it could happen with mostly rational users,
> but even then it's not very likely with most forks. With the blocksize
> issue, there are some people who get very religious about things like
> decentralization or fee markets and think that even 1 MB is too large; I
> could see them making financial sacrifices in order to try to make a
> small-block parallel fork a reality, one that is true to their vision of
> what's needed to make Bitcoin true and pure, or whatever.
>
>
>
>
> On Sep 29, 2015, at 7:04 AM, Gavin Andresen <gavinandresen@gmail•com>
> wrote:
>
> I keep seeing statements like this:
>
> On Tue, Sep 29, 2015 at 9:30 AM, Jonathan Toomim (Toomim Bros) via
> bitcoin-dev <bitcoin-dev@lists•linuxfoundation.org> wrote:
>
>> As a further benefit to hard forks, anybody who is ideologically opposed
>> to the change can continue to use the old version successfully, as long as
>> there are enough miners to keep the fork alive.
>
>
> ... but I can't see how that would work.
>
> Lets say there is a hard fork, and 5% of miners stubbornly refuse to go
> along with the 95% majority (for this thought experiment, it doesn't matter
> if the old rules or new rules 'win').
>
> Lets further imagine that some exchange decides to support that 5% and
> lets people trade coins from that fork (one of the small altcoin exchanges
> would definitely do this if they think they can make a profit).
>
> Now, lets say I've got a lot of pre-fork bitcoin; they're valid on both
> sides of the fork. I support the 95% chain (because I'm not insane), but
> I'm happy to take people's money if they're stupid enough to give it to me.
>
> So, I do the following:
>
> 1) Create a send-to-self transaction on the 95% fork that is ONLY valid on
> the 95% fork (maybe I CoinJoin with a post-fork coinbase transaction, or
> just move my coins into then out of an exchange's very active hot wallet so
> I get coins with a long transaction history on the 95% side of the fork).
>
> 2) Transfer  those same coins to the 5% exchange and sell them for
> whatever price I can get (I don't care how low, it is free money to me-- I
> will still own the coins on the 95% fork).
>
> I have to do step (1) to prevent the exchange from taking the
> transfer-to-exchange transaction and replaying it on the 95% chain.
>
> I don't see any way of preventing EVERYBODY who has coins on the 95% side
> of the fork from doing that. The result would be a huge free-fall in price
> as I, and everybody else, rushes to get some free money from anybody
> willing to pay us to remain idealogically pure.
>
> Does anybody think something else would happen, and do you think that
> ANYBODY would stick to the 5% fork in the face of enormously long
> transaction confirmation times (~3 hours), a huge transaction backlog as
> lots of the 95%'ers try to sell their coins before the price drops, and a
> massive price drop for coins on the 5% fork.
>
> --
> --
> Gavin Andresen
>
>
>
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>

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