Date: Sat, 26 Feb 2022 07:39:36 +0000
To: Paul Sztorc <truthcoin@gmail.com>,
 Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
From: ZmnSCPxj <ZmnSCPxj@protonmail.com>
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Cc: "lightning-dev\\\\@lists.linuxfoundation.org"
 <lightning-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] A Comparison Of LN and Drivechain Security In The
	Presence Of 51% Attackers
Precedence: list


Good morning Paul,


> I don't think I can stop people from being ignorant about Drivechain. But=
 I can at least allow the Drivechain-knowledgable to identify each other.
>
> So here below, I present a little "quiz". If you can answer all of these =
questions, then you basically understand Drivechain:
>
> 0. We could change DC to make miner-theft impossible, by making it a laye=
r1 consensus rule that miners never steal. Why is this cure worse than the =
disease?

Now miners are forced to look at all sideblocks, not optionally do so if it=
 is profitable for them.

> 1. If 100% hashrate wanted to steal coins from a DC sidechain *as quickly=
 as possible*, how long would this take (in blocks)?

13,150 (I think this is how you changed it after feedback from this list, I=
 think I remember it was ~3000 before or thereabouts.)

> 2. Per sidechain per year (ie, per 52560 blocks), how many DC withdrawals=
 can take place (maximum)? How many can be attempted?
>      (Ie, how does the 'train track metaphor' work, from ~1h5m in the "Ov=
erview and Misconceptions" video)?

I hate watching videos, I can read faster than anyone can talk (except mayb=
e Laolu, he speaks faster than I can process, never mind read).

~4 times (assuming 52560 block per year, which may vary due to new miners, =
hashrate drops, etc)

> 3. Only two types of people should ever be using the DC withdrawal system=
 at all.
>   3a. Which two?

a.  Miners destroying the sidechain because the sidechain is no longer viab=
le.
b.  Aggregators of sidechain-to-minechain transfers and large whales.

>   3b. How is everyone else, expected to move their coins from chain to ch=
ain?

Cross-system atomic swaps.
(I use "System" here since the same mechanism works for Lightning channels,=
 and channels are not blockchains.)

>   3c. (Obviously, this improves UX.) But why does it also improve securit=
y?

Drivechain-based pegged transfers are aggregates of many smaller transfers =
and thus every transfer out from the sidechain contributes its "fee" to the=
 security of the peg.

> --
> 4. What do the parameters b and m stand for (in the DC security model)?

m is how much people want to kill a sidechain, 0 =3D everybody would be sad=
 if it died and would rather burn all their BTC forever than continue livin=
g, 1 =3D do not care, > 1 people want to actively kill the sidechain.

b is how much profit a mainchain miner expects from supporting a sidechain =
(do not remember the unit though).
Something like u =3D a + b where a is the mainchain, b is the sidechain, u =
is the total profit.
Or fees?  Something like that.

> 5. How can m possibly be above 1? Give an example of a sidechain-attribut=
e which may cause this situation to arise.

The sidechain is a total scam.
A bug may be found in the sidechain that completely negates any security it=
 might have, thus removing any desire to protect the sidechain and potentia=
lly make users want to destroy it completely rather than let it continue.
People end up hating sidechains completely.

> 6. For which range of m, is DC designed to deter sc-theft?

m <=3D 1

> 7. If DC could be changed to magically deter theft across all ranges of m=
, why would that be bad for sidechain users in general?

Because the sidechain would already be part of mainchain consensus.

> --
> 8. If imminent victims of a DC-based theft, used a mainchain UASF to proh=
ibit the future theft-withdrawal, then how would this affect non-DC users?

If the non-DC users do not care, then they are unaffected.
If the non-DC users want to actively kill the sidechain, they will countera=
ttack with an opposite UASF and we have a chainsplit and sadness and mutual=
 destruction and death and a new subreddit.

> 9. In what ways might the BTC network one day become uncompetitive? And h=
ow is this different from caring about a sidechain's m and b?

If it does not enable scaling technology fast enough to actually be able to=
 enable hyperbitcoinization.

Sidechains are not a scaling solution, so caring about m and b is different=
 because your focus is not on scaling.

> --
> 10. If DC were successful, Altcoin-investors would be harmed. Two Maximal=
ist-groups would also be slightly harmed -- who are these?

Dunno!


Regards,
ZmnSCPxj