Subject: Re: [Bitcoin-development] Scaling Bitcoin with Subchains

From: Peter Todd <[email-masked]>
Date: Tue, 16 Jun 2015 19:17:24 +0100

On Mon, Jun 15, 2015 at 01:15:14PM -0400, Jeff Garzik wrote:
> On Mon, Jun 15, 2015 at 1:09 PM, Pieter Wuille <[email-masked]>
> wrote:
> 
> > It's simple: either you care about validation, and you must validate
> > everything, or you don't, and you don't validate anything. Sidechains do
> > not offer you a useful compromise here, as well as adding huge delays and
> > conplexity.
> >
> 
> As noted to Adam last night - although I agree it adds complexity - side
> chains are one solution that will indeed help with scaling long term.
> Similar to the graph you see with git repos and merges, having aggregation
> chains that arbitrarily fork and then rejoin the main chain are both
> feasible and useful.
> 
> That code & future is a ways away from production, so doesn't help us
> here.  Still, let's not dismiss it as a solution either.

To be clear, it depends on what kind of sidechain.

My off-chain transaction notions are federated sidechains with an
economic incentive to not commit fraud using fidelity bonds; they were
definitely proposed as a scaling solution.

Merge-mined sidechains are not a scaling solution any more than SPV is a
scaling solution because they don't solve the scaling problem for
miners.

Some kind of treechain like sidechain / subchains where what part of the
tree miners can mine is constrained to preserve fairness could be both a
scaling solution, and decentralized, but no-one has come up with a solid
design yet that's ready for production. (my treechains don't qualify for
transactions yet; maybe for other proof-of-publication uses)

Keep in mind that other than preserving mining
decentralization/resisting censorship, we've known how to scale up
blockchains for ages w/ things like (U)TXO commitments and fraud proofs.

-- 
'peter'[:-1]@petertodd.org
0000000000000000127ab1d576dc851f374424f1269c4700ccaba2c42d97e778