Re: [bitcoin-dev] Segregated Witness features wish list

2015-12-10 Thread Tamas Blummer via bitcoin-dev
Note that the unused space in coin base input script allows us to soft-fork an 
additional SW Merkle tree root into the design,
therefore please make sure the new SW data structure also has a new slot for 
future extension.

Tamas Blummer

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Re: [bitcoin-dev] Segregated Witness features wish list

2015-12-10 Thread Gregory Maxwell via bitcoin-dev
On Thu, Dec 10, 2015 at 6:47 AM, jl2012--- via bitcoin-dev
 wrote:
> 4. Sum of fee, sigopcount, size etc as part of the witness hash tree: for

I should have also commented on this: the block can indicate how many
sum criteria there are; and then additional ones could be soft-forked
in. Haven't tried implementing it yet, but there you go. :)
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Re: [bitcoin-dev] Segregated Witness features wish list

2015-12-10 Thread Bryan Bishop via bitcoin-dev
On Thu, Dec 10, 2015 at 12:47 AM, jl2012 wrote:
> 3. SIGHASH_WITHINPUTVALUE [1]: there are many SIGHASH proposals but this one
> has the highest priority as it makes offline signing much easier.

nhashtype proposal:
https://github.com/scmorse/bitcoin-misc/blob/master/sighash_proposal.md

OP_CODESEPARATOR:
http://lists.linuxfoundation.org/pipermail/bitcoin-dev/2015-April/007802.html

summary email about sighash type proposals (which IIRC you saw, so
leaving this link here is mainly for the benefit of others):
https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2015-August/010759.html

- Bryan
http://heybryan.org/
1 512 203 0507
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Re: [bitcoin-dev] Segregated Witness features wish list

2015-12-10 Thread Gregory Maxwell via bitcoin-dev
On Thu, Dec 10, 2015 at 6:47 AM, jl2012--- via bitcoin-dev
 wrote:
> It seems the current consensus is to implement Segregated Witness. SW opens
> many new possibilities but we need a balance between new features and
> deployment time frame. I'm listing by my priority:

> 2. Deployment time frame: I prefer as soon as possible, even if none of the 
> following new features are implemented.

Thanks, I agree there.

A point to keep in mind:  Segregated Witness was specifically designed
to make script changes / improvements / additions / total rewrites no
harder to do _after_ SW then they would be do do along with it.  For
many people the "ah ha! lets do this" was realizing it could be a
pretty clean soft-fork.  For me, it was realizing that we could
structure Segwit in a way that radically simply future script updates
... and in doing so avoid a getting trapped by a rush to put in every
script update someone wants.

This is achieved by having the 'version' byte(s) at the start of the
witness program. If the witness program prefix is unrecognized it
means RETURN TRUE.  This recaptures the behavior that seems to have
been intended by OP_VER in the earliest versions of the software, but
actually works instead of giving every user the power to hardfork the
system at any time. :)  This escapes much of the risk in script
changes, as we no longer need to worry about negation, or other
interactions potentially breaking things.  A new version flag can have
its whole design crafted as if it were being created on a clean slate.

Optimizing layout and such I think makes sense, but I think we should
consider any script enhancements completely off the table for SW;
otherwise the binding will delay deployment and increase complexity. I
want most of those things too (a couple I disagree with) and a few of
them we could do quite quickly-- but no need to bind them up; post SW
and esp with version bits we could deploy them quite rapidly and on
their own timeframes.


> Multiplication and division may still considered to be risky and not very 
> useful?

Operations like these make sense with fixed with types, when they are
over arbitrary bignums, they're a complexity nightmare...  as
demonstrated by Bitcoin. :)


RE: OP_DUPTOALTSTACK  yea, I've wanted that several times (really I've
been sad that there isn't just a stack flag on every manipulation
instruction).
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