Subject: Re: [bitcoin-dev] Drivechain RfD -- Follow Up

From: Paul Sztorc <[email-masked]>
Date: Wed, 12 Jul 2017 20:26:56 -0400

The confusion below stems from his conflation of several different ideas.

I will try to explicitly clarify a distinction between several types of
user (or, "modes" of use if you prefer):

[DC#0] -- Someone who does not upgrade their Bitcoin software (and is
running, say, 0.13). However, they experience the effects of the new
rules which miners add (as per the soft fork[s] to add drivechain
functionality and individual drivechains).
[DC#1] -- Someone who always upgrades to the latest version of the
Bitcoin software, but otherwise has no interest in running/using sidechains.
[DC#2] -- Someone who upgrades to the latest Bitcoin version, and
decides to also become a full node of one or more sidechains, but who
ever actually uses the sidechains.
[DC#3] -- Someone who upgrades their software, runs sidechain full
nodes, and actively moves money to and from these.

On 7/12/2017 6:43 PM, Tao Effect wrote:
>
> I am now looking closer again at step number 4 in the Drivechain
> specification [2]:
>
>     4. Everyone waits for a period of, say, 3 days. This gives
>     everyone an opportunity to make sure the same WT^ is in both the
>     Bitcoin coinbase and the Sidechain header. If they’re different,
>     everyone has plenty of time to contact each other, figure out what
>     is going on, and restart the process until its right.
>
> It seems to me that where our disagreement lies is in this point.
> The Drivechain spec seems to claim that its use of anyone-can-pay is
> the same as P2SH (and in later emails you reference SegWit as well).
> Is this really true?
FYI that document is nearly two years old, and although it is still
overwhelmingly accurate, new optimizations allow us (I think) to push
the waiting period to several weeks and the total ACK counting period up
to several months.

[DC#0] Yes
[DC#1] Yes
[DC#2] Yes
[DC#3] Yes

Because if a node doesn't have the sidechain's information, it will just
assume every withdrawal is valid. This is comparable to someone who
still hasn't upgraded to support P2SH, in cases [DC#0] and [#1].

(And this is the main advantage of DC over extension blocks).

> 2. Per the question in [1], it's my understanding that P2SH
> transactions contain all of the information within themselves for full
> nodes to act as a check on miners mishandling the anyone-can-spend
> nature of P2SH transactions. However, that does not seem to be the
> case with WT^ transactions.
[DC#0] They do.
[DC#1] They do.
[DC#2] They do.
[DC#3] They do.

Again, from the perspective of a mainchain user, every withdrawal is valid.

> In P2SH txns, there is no need for anyone to, as the Drivechain spec
> says, "to contact each other, figure out what is going on". Everything
> just automatically works.
There is no *need* to this in Drivechain, either, for [DC#0] or [DC#1].

[DC#2] and [DC#3] would certainly have an interest in understanding what
is going on, but that has absolutely nothing whatsoever to do with
Bitcoin Core and so is off-topic for this mailing list.

> If the security of WT^ transactions could be brought up to actually be
> in line with the security of P2SH and SegWit transactions, then I
> would have far less to object to.
Somehow I doubt it.

Paul