[bitcoin-dev] Segregated Witness in the context of Scaling Bitcoin

Corey Haddad corey3 at gmail.com
Thu Dec 17 07:54:41 UTC 2015

A planned hardfork, similar to certain softforks, leaves users with some
reduction in security.  It does not leave them defenseless.  Consider the

1: Hard to be robbed on the basis of hashpower.

In reality the old chain will see mining all but stop, and blocks would be
hours to days apart even if a couple percentage points of hashpower failed
to switch over.  Six confirmations would certainly take days.  If the fork
can be scheduled at the beginning of a difficulty period, the old chain
would almost certainly not even ever make it to the next retargeting.

2: Hard to be robber on the basis of awareness.

Expect there to be fairly widespread coverage in the Bitcoin press, and as
the fork draws near, maybe coverage in business and tech publications.
Further, the alert keys will certainly be used, so node operators will get
the message directly.

3: There still needs to be a targeted attack by a fraudster on an unaware
node operator.

To fall victim, one needs to give up something of value to an attacker in
exchange for Bitcoins (on the old chain).  The typical uninitiated
full-node user (probably a small subset anyway) is typically going to be
buying bitcoin from a trusted source, and then saving or spending them, or
perhaps gambling.  They are not, typically, going to be providing a service
or selling goods in exchange for Bitcoin unless they are at least somewhat
aware of what is going on in the Bitcoin space.  It's possible, of course,
but we are talking about small numbers here of people who fit the above.

All three parts of the above would have to go perfectly wrong for someone
to loose out.  Someone somewhere will probably get scammed as a result of a
hardfork.  That stinks, and we should make reasonable efforts to help them
avoid that fate.  But at this point in Bitcoin's development, it is still
in beta, it's still an economic experiment, and we can't allow the software
to become hamstrung out of fear that some inattentive user might bungle
their security.  If they merely waited for 6 confirmations, as is the
standard advice, they would be waiting for days.  If that along doesn't
give them a hint that something is wrong, it might still be too early days
for them to be playing with Bitcoin for anything important.

I support a hardfork deployment that takes 80% of hashpower activate + a
4-month delay.

On Wed, Dec 16, 2015 at 9:32 PM, jl2012 via bitcoin-dev <
bitcoin-dev at lists.linuxfoundation.org> wrote:

> There are at least 2 proposals on the table:
> 1. SWSF (segwit soft fork) with 1MB virtual block limit, approximately
> equals to 2MB actual limit
> 2. BIP102: 2MB actual limit
> Since the actual limits for both proposals are approximately the same, it
> is not a determining factor in this discussion
> The biggest advantage of SWSF is its softfork nature. However, its
> complexity is not comparable with any previous softforks we had. It is
> reasonable to doubt if it could be ready in 6 months
> For BIP102, although it is a hardfork, it is a very simple one and could
> be deployed with ISM in less than a month. It is even simpler than BIP34,
> 66, and 65.
> So we have a very complicated softfork vs. a very simple hardfork. The
> only reason makes BIP102 not easy is the fact that it's a hardfork.
> The major criticism for a hardfork is requiring everyone to upgrade. Is
> that really a big problem?
> First of all, hardfork is not a totally unknown territory. BIP50 was a
> hardfork. The accident happened on 13 March 2013. Bitcoind 0.8.1 was
> released on 18 March, which only gave 2 months of grace period for everyone
> to upgrade. The actual hardfork happened on 16 August. Everything completed
> in 5 months without any panic or chaos. This experience strongly suggests
> that 5 months is already safe for a simple hardfork. (in terms of
> simplicity, I believe BIP102 is even simpler than BIP50)
> Another experience is from BIP66. The 0.10.0 was released on 16 Feb 2015,
> exactly 10 months ago. I analyze the data on https://bitnodes.21.co and
> found that 4600 out of 5090 nodes (90.4%) indicate BIP66 support.
> Considering this is a softfork, I consider this as very good adoption
> already.
> With the evidence from BIP50 and BIP66, I believe a 5 months
> pre-announcement is good enough for BIP102. As the vast majority of miners
> have declared their support for a 2MB solution, the legacy 1MB fork will
> certainly be abandoned and no one will get robbed.
> My primary proposal:
> Now - 15 Jan 2016: formally consult the major miners and merchants if they
> support an one-off rise to 2MB. I consider approximately 80% of mining
> power and 80% of trading volume would be good enough
> 16 - 31 Jan 2016: release 0.11.3 with BIP102 with ISM vote requiring 80%
> of hashing power
> 1 Jun 2016: the first day a 2MB block may be allowed
> Before 31 Dec 2016: release SWSF
> My secondary proposal:
> Now: Work on SWSF in a turbo mode and have a deadline of 1 Jun 2016
> 1 Jun 2016: release SWSF
> What if the deadline is not met? Maybe pushing an urgent BIP102 if things
> become really bad.
> In any case, I hope a clear decision and road map could be made now. This
> topic has been discussed to death. We are just bringing further uncertainty
> if we keep discussing.
> Matt Corallo via bitcoin-dev 於 2015-12-16 15:50 寫到:
>> A large part of your argument is that SW will take longer to deploy
>> than a hard fork, but I completely disagree. Though I do not agree
>> with some people claiming we can deploy SW significantly faster than a
>> hard fork, once the code is ready (probably a six month affair) we can
>> get it deployed very quickly. It's true the ecosystem may take some
>> time to upgrade, but I see that as a feature, not a bug - we can build
>> up some fee pressure with an immediate release valve available for
>> people to use if they want to pay fewer fees.
>>  On the other hand, a hard fork, while simpler for the ecosystem to
>> upgrade to, is a 1-2 year affair (after the code is shipped, so at
>> least 1.5-2.5 from today if we all put off heads down and work). One
>> thing that has concerned me greatly through this whole debate is how
>> quickly people seem to think we can roll out a hard fork. Go look at
>> the distribution of node versions on the network today and work
>> backwards to get nearly every node upgraded... Even with a year
>> between fork-version-release and fork-activation, we'd still kill a
>> bunch of nodes and instead of reducing their security model, lead them
>> to be outright robbed.
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