Bitcoin Chainsplit: Segwit2x, Replay Protection, and Security Risks
[Chris Ellis] What follows is an informal chat about the
upcoming Bitcoin chainsplit in November, .. most commonly referred to as “SegWit2x.”
In this conversation, Gibus, MrHodl, and others .. ask Bitcoin Core developer
Luke-Jr (@LukeDashjr) for his opinion .. about replay protection and
the possible security risks. The content found herein should be taken
as open-minded conversation. Cryptocurrency is an emerging topic of research and
you’re encouraged to carry out your own due-diligence. We’d love to get your feedback. If you have any corrections,
please post them in the comments below. [Gibus] I’m just a little more worried than
MrHodl about this SegWit2x thinking, that if we have 95% of the miners switch over,
without replay protection, we’d just end up .. with two chains, where one is basically
confirming and the other one is just having .. a more and more clogged up memepool.
As you can’t split the coins (in my understanding), .. then really there’s just a ‘functional’
and a ‘non-functional’ chain. It would be really, really hard to get
people to just wait with 5% hashrate. We’re talking like 40 weeks for difficulty re-target.
I’m scared that people will just go with the 2x chain. As this time, the market can’t just dump one and hold
the other, you know? Did you get any of that, Luke? [LukeDashjr] Yeah, I think so.
You can split the coins, however. [Gibus] You can? [LukeDashjr] Yes, it’s just not
automatic on the fork day. [Gibus] How would you go about this?
Is there a way to… [LukeDashjr] The locktime check should work. [Chris Ellis] Ah, you put an nLockTime on it.
[Gibus] Hmm. [Chris Ellis] That’s interesting. [MrHodl] I didn’t think of that. [Chris Ellis] Yeah.
[davyd] Haha, you’re like “Luke, help me!” [davyd] And then he helped! [Chris Ellis] The smart person
comes in and schools us all. [Gibus] So nLockTime.. wait,
how would that not go into two chains? [LukeDashjr] First you send the one for
the chain that’s further, with more blocks, .. with the nLockTimes that will
only confirm on that chain. Then you double-spend it with
replace-by-fee (RBF) on the other chain. [Gibus] Okay. How could that not be
replayed on the original? Okay, yeah. It’s got confirmed on the first one. [LukeDashjr] You don’t even need RBF, really. The locktime will prevent it from getting
mined on the slower chain anyway. [MrHodl] Holy shit, so you could split
coins with no replay protection? [Gibus] Yeah. [LukeDashjr] Yes, you just
need to actually make an effort to do it. [MrHodl] Until somebody automates it,
until somebody sets something up, right? [Gibus] How would you do it without
replace-by-fee though, because… .. I got the first way, but the
second way I’m not sure. [LukeDashjr] Well, say that the faster blockchain
is 200 blocks further than the slower blockchain… [Gibus] Yup. [LukeDashjr] .. then you
use the lock and you say: “The block height has to
be block #200,” for example.” The faster blockchain will confirm that
immediately and the slower blockchain… .. won’t even relay the transaction until
it gets to that block, which could be- [MrHodl] Ah! [Gibus] Great. Thank you.
[MrHodl] Haha… [Gibus] That’s a good one. [Gibus] So it takes some time, but it’s
pretty easy after this. Okay. [LukeDashjr] Yeah. I mean, if you don’t have-
I guess in this case there’s no chance… .. of reorg, but in other cases if the faster
blockchain wasn’t significantly faster, .. it would get wiped out by
the other chain anyway. [Gibus] I hear you. Thanks for clearing that up.
That’s already a pretty important aspect, .. it reassures me of it. But we still have the
problem that… Okay, it’s a big “if,” but… .. if they have 90-95% and are sticking with it,
if this is really a grand plan to force us, it’s still going to be a very long battle. [LukeDashjr] There’s no reason to think
that they have that much hashrate anyway. [MrHodl] That’s what I said! Just like what I said. [Gibus] Yeah, we’re just trying to see,
we’re theorising the worst case scenarios. But what do you think? Do you have anything to share
on this? How do you think this is going to play out? Close to Bcash? Very low support?
Can you hear me, Luke? [LukeDashjr] Yeah, I thought you were
asking someone else something. [Gibus] No, I was wondering what your
thoughts were, if you had a rough prediction… .. of how this is going to go?
Do you have any idea? [davyd] Haven’t you seen his fork? [davyd] It’s the only one he-
[LukeDashjr] Well, if we learned anything from UASF, .. miners just won’t do it.
[Gibus] Hopefully, yeah. But they hadn’t signed for Bcash.
We all know the New York Agreement .. and when they signed it is kind of bullshit,
because they didn’t even sign for code. Some of them didn’t know the exact details.
But theoretically they’re saying they still have… .. a majority of the hashrate moving over.
Not to take- It probably won’t happen that way, but you’re not worried at all?
[LukeDashjr] Bcash changed the difficulty adjustment… .. so that it would adjust down to meet the lower
difficulty, whereas 2x – if they split off – they’re going… .. to just have a close-to-zero price and
they’re not going to be making the money… .. they need to pay their electric bill.
[MrHodl] It all comes back down to the market, man. That’s what we were saying earlier.
Maybe some could mine at a loss longer than others, but as time goes on, less and less will be
able to mine at a loss. It’s only a matter of time… .. before everyone turns back.
[LukeDashjr] The only reason Bcash isn’t at a loss .. right now is because they adjusted the difficulty down.
[MrHodl] They’re still running at a loss. [LukeDashjr] Not significant.
[MrHodl] Yeah, not as bad as this would be. All right Luke, thanks!
That was our only concern. Thank you. [Gibus] Yeah, thanks Luke! [ALL] Thanks!