Subject: Re: [bitcoin-dev] Capacity increases for the Bitcoin system.

From: Mark Friedenbach <[email-masked]>
Date: Wed, 9 Dec 2015 16:46:31 +0800

My apologies for the apparent miscommunication earlier. It is of interest
to me that the soft-fork be done which is necessary to put a commitment in
the most efficient spot possible, in part because that commitment could be
used for other data such as the merged mining auxiliary blocks, which are
very sensitive to proof size.

Perhaps we have a different view of how the commitment transaction would be
generated. Just as GBT doesn't create the coinbase, it was my expectation
that it wouldn't generate the commitment transaction either -- but
generation of the commitment would be easy, requiring either the coinbase
txid 100 blocks back, or the commitment txid of the prior transaction (note
this impacts SPV mining). The truncation shouldn't be an issue because the
commitment txn would not be part of the list of transactions selected by
GBT, and in any case the truncation would change the witness data which
changes the commitment.

On Wed, Dec 9, 2015 at 4:03 PM, Gregory Maxwell via bitcoin-dev <
[email-masked]> wrote:

> On Wed, Dec 9, 2015 at 7:54 AM, Jorge Timón <[email-masked]> wrote:
> > From this question one could think that when you said "we can do the
> > cleanup hardfork later" earlier you didn't really meant it. And that
> > you will oppose to that hardfork later just like you are opposing to
> > it now.
> > As said I disagree that making a softfork first and then move the
> > commitment is less disruptive (because people will need to adapt their
> > software twice), but if the intention is to never do the second part
> > then of course I agree it would be less disruptive.
> > How long after the softfork would you like to do the hardfork?
> > 1 year after the softfork? 2 years? never?
>
> I think it would be logical to do as part of a hardfork that moved
> commitments generally; e.g. a better position for merged mining (such
> a hardfork was suggested in 2010 as something that could be done if
> merged mining was used), room for commitments to additional block
> back-references for compact SPV proofs, and/or UTXO set commitments.
> Part of the reason to not do it now is that the requirements for the
> other things that would be there are not yet well defined. For these
> other applications, the additional overhead is actually fairly
> meaningful; unlike the fraud proofs.
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