[Bitcoin-development] Pay to MultiScript hash:

[Jeremy]

* the general cost of any network-wide change, versus P2SH which is
already analyzed by devs, rolled out and working
* the cost of updating everybody to relay this new transaction type,
whereas P2SH Just Works already
fair -- I think that there may be a big benefit realizable with this kind
of system.

* cost of increasing rate of UTXO growth versus P2SH
This operation is similar in cost to multisig? Although I suppose there is
the proposal to make all multisigs p2sh

* the cost of P2SH output is predictable, versus less predictable outputs
 * "default public", versus P2SH's "default private"
-- Can you elaborate on these?

I think part of the problem is that there is low incentive for
development/cataloging  of these useful types of script because there isn't
a horizon on getting them broadcastable by nodes other than testnet? Even
with pay to script hash it is still currently relegated to a subset of
script types iirc (I think I'm wrong on this one maybe (hopefully) -- if
so, let's get writing!)?



Hmm... another idea... what about doing a p2sh with a switch statement, ie:

OP_HASH160 <script set hash> OP_EQUAL

payable by:

{signatures...} <scriptX> <<script1 hash>, <script2 hash>...<scriptN hash>
in sorted order> OP_DUP

And then executed like a normal p2sh transaction except before the
<scriptX> is run, the set of hashes is checked for set membership (can't
find a concise way to express this, but it should be doable within the
current framework of p2sh processing).

Which lets you select one of n scripts each 520 bytes long without bloating
the utxo pool more than a p2sh, the cost being purely on disk.

In theory, this could represent a space savings on disk longterm for
regular p2sh. ie, if I have two 2 of 3 groups I want to be able to spend,
this system would represent an overall space savings.


Adding some kind of "function-hash-pointer jump table / switch statement"
could be pretty cool in terms of space savings as well as allowing for more
complicated scripts to be built.



On Thu, Jul 17, 2014 at 2:21 AM, Jeff Garzik <jgarzik at bitpay.com> wrote:

> In a system like bitcoin, where the system has to keep running, you
> have to consider how to roll out upgrades, and the costs associated
> with that.
> * the general cost of any network-wide change, versus P2SH which is
> already analyzed by devs, rolled out and working
> * the cost of P2SH output is predictable, versus less predictable outputs
> * the cost of updating everybody to relay this new transaction type,
> whereas P2SH Just Works already
> * cost of increasing rate of UTXO growth versus P2SH
> * "default public", versus P2SH's "default private"
>
> It is true that publishing the script in the txout has the advantage
> of being easily audited by third parties scanning the blockchain, but
> in the interest of space efficiency you may accomplish the same thing
> by offering the script upon request out-of-band.  The script is
> hash-sealed by the P2SH address, enabling perfect proof.
>
> Don't have a transcript handy, but these things are usually logged and
> google-searchable.
>
> In any case, it would be nice to get together and start building a
> "cookbook" of useful scripts like the ones you've been describing.
> The power of bitcoin scripts is only beginning to be explored.  Use
> cases and examples are very helpful.
>
>
>
> On Thu, Jul 17, 2014 at 1:59 AM, Jeremy <jlrubin at mit.edu> wrote:
> > Additional costs would be in terms of A) chance of user error/application
> > error -- proposed method is much simpler, as well as extra bytes for
> control
> > flow ( 4 per script if I am counting right).
> >
> >
> > The costs on a normal script do seem slightly more friendly, except this
> > method allows for hidden-till-spent permission groups, as well as as
> smaller
> > blockchain bloat overall (if scriptSig script has to store the logic for
> all
> > the potential permission group, it will be a larger script  versus only
> > needing one permission group's script). An added benefit could also be in
> > blockchain analysis -- you can actively monitor the utxo pool for your
> known
> > associated scripts, whereas you couldn't for specialty scripts assembled
> per
> > group. Enables repeated spends with groups as a "cost object" w/o having
> to
> > recall all participants. ie, pay to the same perm groups as the other
> > employee did last time, but include me as a root this time.
> >
> >
> > Do you have a transcript of that chat by any chance? An interesting way
> to
> > do that would be to push the sigs onto the stack & have implicit orders,
> > then do expressions with their aliases, and then be able to assign
> "spending
> > groups".
> > ex:
> > code_sep
> > push script0
> > push script1
> > push script2
> > push script3
> > group_sep
> > mkgroup_2, 0,1      ; the id will be 4
> > mkgroup_3, 0,2,3   ; the id will be 5
> > mkUnionGroup_2, 4,5 ; the id will be 6
> > 2_of_3_group 0, 1, 2
> > mkIntersectionGroup_2 5, 6
> > complement_last  ; complements last group, mutation
> > del_group 1          ; deletes the group #1, groups then reindex after
> > deletion (maybe the group was useful base class).
> > etc...
> > multisig check perm groups (checks if any groups on stack are valid from
> > script)
> >
> >
> > or even something like adding a little SAT scripting language with an
> eval.
> >
> > push script0
> > push script1
> > push script2
> > push script3
> > push <a=(1 & 2 & 0), b=a-1, a | 3 | b >
> > eval
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > On Thu, Jul 17, 2014 at 12:52 AM, Jeff Garzik <jgarzik at bitpay.com>
> wrote:
> >>
> >> On Wed, Jul 16, 2014 at 1:56 PM, Jeremy <jlrubin at mit.edu> wrote:
> >> > Right now, this could be expressed multiple ways (ie, using an op_dup
> if
> >> > then else chain) , but all would incur additional costs in terms of
> >> > complicated control flows. Instead, I would propose:
> >>
> >> Can you quantify "additional costs in terms of complicated control
> flows"?
> >>
> >>
> >> > There is an implication in terms of increased utxo pool bloat, but
> also
> >> > an
> >> > implication in terms of increased txn complexity (each 20 byte hash
> >> > allows
> >> > for a 500 byte script, only one of the 500 byte scripts has to be
> >> > permanently stored on blockchain).
> >>
> >> When considering these costs, using a normal P2SH output + a script
> >> with OP_IF and friends seems more straightforward?
> >>
> >> Doing boolean logic with multisig groups is quite possible, e.g.
> >> "group AND group", "group OR (group AND group)" etc.  Definitely a
> >> valid use case.  I discussed how to do this on IRC with gmaxwell
> >> several months ago.  I call it "multi-multisig" for lack of a better
> >> name.
> >
> >
> >
> >
> > --
> > Jeremy Rubin
>
>
>
> --
> Jeff Garzik
> Bitcoin core developer and open source evangelist
> BitPay, Inc.      https://bitpay.com/
>



-- 
Jeremy Rubin
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