[Bitcoin-development] BIP - Selector Script

[Bitcoin-development] BIP - Selector Script

[Tier Nolan]

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This is a BIP to allow the spender to choose one of multiple standard
scripts to use for spending the output.

https://github.com/TierNolan/bips/blob/bip4x/bip-0045.mediawiki

This is required as part of the atomic cross chain transfer protocol.  It
is required so that outputs can be retrieved, if the process ends before
being committed.

https://bitcointalk.org/index.php?topic=193281.msg2224949#msg2224949

The script allows multiple standard scripts to be included in the
scriptPubKey.

When redeeming the script the spender indicates which of the standard
scripts to use.

Only one standard script is actually executed, so the only cost is the
extra storage required.

A more ambitious change would be a soft fork like P2SH, except the spender
is allowed to select from multiple hashes.  Effectively, it would be
"Multi-P2SH".

This gets much of the benefits of MAST, but it requires a formal soft fork
to implement.

If there is agreement, I can code up the reference implementation as a PR.
The multi-P2SH might actually be easier.

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Re: [Bitcoin-development] BIP - Selector Script

[Luke-Jr]

I believe you meant to link here instead?
    https://github.com/TierNolan/bips/blob/bip4x/bip-0046.mediawiki

This looks reasonable from a brief skim over, but does not define any use 
cases (it mentions "necessary for atomic cross chain transfers", but does not 
explain how it is useful for that - perhaps that belongs in another BIP you 
haven't written yet, though). IMO, it should also require P2SH.

Luke


On Friday, April 25, 2014 6:49:35 PM Tier Nolan wrote:
> This is a BIP to allow the spender to choose one of multiple standard
> scripts to use for spending the output.
> 
> https://github.com/TierNolan/bips/blob/bip4x/bip-0045.mediawiki
> 
> This is required as part of the atomic cross chain transfer protocol.  It
> is required so that outputs can be retrieved, if the process ends before
> being committed.
> 
> https://bitcointalk.org/index.php?topic=193281.msg2224949#msg2224949
> 
> The script allows multiple standard scripts to be included in the
> scriptPubKey.
> 
> When redeeming the script the spender indicates which of the standard
> scripts to use.
> 
> Only one standard script is actually executed, so the only cost is the
> extra storage required.
> 
> A more ambitious change would be a soft fork like P2SH, except the spender
> is allowed to select from multiple hashes.  Effectively, it would be
> "Multi-P2SH".
> 
> This gets much of the benefits of MAST, but it requires a formal soft fork
> to implement.
> 
> If there is agreement, I can code up the reference implementation as a PR.
> The multi-P2SH might actually be easier.

Re: [Bitcoin-development] BIP - Selector Script

[Peter Todd]

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On Fri, Apr 25, 2014 at 07:17:48PM +0000, Luke-Jr wrote:
> I believe you meant to link here instead?
>     https://github.com/TierNolan/bips/blob/bip4x/bip-0046.mediawiki
> 
> This looks reasonable from a brief skim over, but does not define any use 
> cases (it mentions "necessary for atomic cross chain transfers", but does not 
> explain how it is useful for that - perhaps that belongs in another BIP you 
> haven't written yet, though). IMO, it should also require P2SH.

Keep in mind that P2SH redeemScripts are limited to just 520 bytes;
there's going to be many cases where more complex transactions just
can't be encoded in P2SH at all.

-- 
'peter'[:-1]@petertodd.org
00000000000000006407c80d5d4506a4253b4b426e0c7702963f8bf91e7971aa

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Re: [Bitcoin-development] BIP - Selector Script

[Tier Nolan]

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On Fri, Apr 25, 2014 at 8:58 PM, Peter Todd <pete@petertodd.org> wrote:

> Keep in mind that P2SH redeemScripts are limited to just 520 bytes;
> there's going to be many cases where more complex transactions just
> can't be encoded in P2SH at all.
>

True.  Having said that, this is just a change to isStandard(), rather than
a protocol change.

These transactions can already be mined into blocks.


> --
> 'peter'[:-1]@petertodd.org
> 00000000000000006407c80d5d4506a4253b4b426e0c7702963f8bf91e7971aa
>
>
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Re: [Bitcoin-development] BIP - Selector Script

[Tier Nolan]

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On Fri, Apr 25, 2014 at 8:17 PM, Luke-Jr <luke@dashjr.org> wrote:

> I believe you meant to link here instead?
>     https://github.com/TierNolan/bips/blob/bip4x/bip-0046.mediawiki
>
> Yeah, sorry.


> This looks reasonable from a brief skim over, but does not define any use
> cases (it mentions "necessary for atomic cross chain transfers", but does
> not
> explain how it is useful for that - perhaps that belongs in another BIP you
> haven't written yet, though).


One use case should be enough.  The atomic cross chain proposal has been
discussed for a while.  It feels like bitcoin works on an "ask permission
first" basis.

It always stalls at the fact that non-standard transactions are hard to get
confirmed on other coins.  It is hard to find pools on other coins which
have weaker isStandard() checks.  The timeouts have to be set so that they
are long enough to guarantee that transactions are accepted before they
expire.

A testnet to testnet transfer is the best that would be possible at the
moment.

I don't think the cross chain system needs a BIP (except to justify this
one).

If cross chain transfer become popular, then it would be useful to ensure
that clients are interoperable, but first things first.  If the
transactions aren't accepted in any chains, then everything stalls.

Secure transfers require that the malleability issue is fixed, but that is
a separate issue.  I am assuming that will be fixed at some point in the
future, since micro-payment channels also requires that it is fixed.


> IMO, it should also require P2SH.
>

It could be restricted to only P2SH, I don't think there would be a loss in
doing that.

Personally, I would make it so that P2SH is mandatory after a certain
time.  It makes distributed verification of the block chain easier.
Everything needed to verify a script is present in the transaction (except
that the output actually exists).

A soft fork that expands P2SH functionality would be even better, but I
would rather not let the best be the enemy of the good.

>
>
> Luke
>
>
> On Friday, April 25, 2014 6:49:35 PM Tier Nolan wrote:
> > This is a BIP to allow the spender to choose one of multiple standard
> > scripts to use for spending the output.
> >
> > https://github.com/TierNolan/bips/blob/bip4x/bip-0045.mediawiki
> >
> > This is required as part of the atomic cross chain transfer protocol.  It
> > is required so that outputs can be retrieved, if the process ends before
> > being committed.
> >
> > https://bitcointalk.org/index.php?topic=193281.msg2224949#msg2224949
> >
> > The script allows multiple standard scripts to be included in the
> > scriptPubKey.
> >
> > When redeeming the script the spender indicates which of the standard
> > scripts to use.
> >
> > Only one standard script is actually executed, so the only cost is the
> > extra storage required.
> >
> > A more ambitious change would be a soft fork like P2SH, except the
> spender
> > is allowed to select from multiple hashes.  Effectively, it would be
> > "Multi-P2SH".
> >
> > This gets much of the benefits of MAST, but it requires a formal soft
> fork
> > to implement.
> >
> > If there is agreement, I can code up the reference implementation as a
> PR.
> > The multi-P2SH might actually be easier.
>
>
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Re: [Bitcoin-development] BIP - Selector Script

[Gregory Maxwell]

On Fri, Apr 25, 2014 at 1:02 PM, Tier Nolan <tier.nolan@gmail.com> wrote:
>> This looks reasonable from a brief skim over, but does not define any use
>> cases (it mentions "necessary for atomic cross chain transfers", but does
>> not
>> explain how it is useful for that - perhaps that belongs in another BIP
>> you
>> haven't written yet, though).
> One use case should be enough.  The atomic cross chain proposal has been
> discussed for a while.  It feels like bitcoin works on an "ask permission
> first" basis.

You're reading that response the wrong way. It isn't in any way
opposed to the specification, it's pointing out that the specification
is _unclear_ about the applications, it mentions one but doesn't
explain it and it wouldn't be apparent to all readers. Thats all.

It could be clarified by saying something like "allows spending to be
controlled by the publication of information, for example in another
transaction so that they can only be completed atomically [citation to
a revision of the contracts page]".

Re: [Bitcoin-development] BIP - Selector Script

[Luke-Jr]

On Friday, April 25, 2014 8:02:41 PM Tier Nolan wrote:
> I don't think the cross chain system needs a BIP (except to justify this
> one).
> 
> If cross chain transfer become popular, then it would be useful to ensure
> that clients are interoperable, but first things first.  If the
> transactions aren't accepted in any chains, then everything stalls.

I think you may be misunderstanding what BIPs are. They do not force nodes to 
take on any given relay/mining policy (thus, BIPs should never talk about 
IsStandard at all). They define standard for interoperability between 
software. So, if you want nodes to relay these transactions, you need to 
convince them, not merely write a BIP for the transaction format. Defining a 
BIP for cross-chain trading would be one way to do that.

> Secure transfers require that the malleability issue is fixed, but that is
> a separate issue.  I am assuming that will be fixed at some point in the
> future, since micro-payment channels also requires that it is fixed.

The malleability "issue" has been known for years.
I wouldn't expect any special effort made to fix it...

> A soft fork that expands P2SH functionality would be even better, but I
> would rather not let the best be the enemy of the good.

There is some ongoing discussion of a softfork to basically redo the Script 
language entirely, but it will take quite a bit of time and development before 
we'll see it in the wild.

Luke

P.S. Did the BIP editor assign these numbers? If not, best to keep them 
numberless until assigned, to avoid confusion when people Google the real BIP 
44 and 45...

Re: [Bitcoin-development] BIP - Selector Script

[Tier Nolan]

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On Fri, Apr 25, 2014 at 9:26 PM, Luke-Jr <luke@dashjr.org> wrote:

> They define standard for interoperability between
> software. So, if you want nodes to relay these transactions, you need to
> convince them, not merely write a BIP for the transaction format.


I agree with you in theory, each miner could decide their inclusion rules
for themselves.

In practice, if the reference client is updated, then most miners will
accept those transactions.  In addition, it would eventually propagate to
alt-coins (or at least the supported ones).

I could simply submit the changes as a pull request for the reference
client, but I was hoping that by doing it this way, it would increase the
odds of it being accepted.


> Defining a BIP for cross-chain trading would be one way to do that.
>

I don't think it quite requires the same coordination in the short term.  I
could write up the sequence as an info BIP.

The malleability "issue" has been known for years.
> I wouldn't expect any special effort made to fix it...
>

It is possible to tweak the protocol so that it still works.  However, it
means that 3rd parties are required (that could go in the BIP too).


> There is some ongoing discussion of a softfork to basically redo the Script
> language entirely, but it will take quite a bit of time and development
> before
> we'll see it in the wild.
>

Implementing multi-P2SH gets a lot of the benefits of MAST, in terms of
efficiency.


>
> Luke
>
> P.S. Did the BIP editor assign these numbers? If not, best to keep them
> numberless until assigned, to avoid confusion when people Google the real
> BIP
> 44 and 45...
>

Not yet, but that is just my personal repo.  I did email gmaxwell, but he
said that they can't be assigned until some discussion has happened.

I take your point that the name appears in the link though, so could cause
issues with searching.


>
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Re: [Bitcoin-development] BIP - Selector Script

[Mark Friedenbach]

I think you're misunderstanding the point. The way you get IsStandard
changed is that you make an application-oriented BIP detailing the use
of some new standard transaction type (say, generalized hash-locked
transactions for atomic swaps). We then discuss that proposal for its
technical merits and reach consensus about the best way to do, for
example, cross-chain atomic swaps. It is then implemented.

So please, focus on some BIP(s) detailing applications of hash-locked
transactions, and we will engage more constructively -- I promise that I
will as cross-chain atomic swaps scratch my itch as well.

On 04/25/2014 01:48 PM, Tier Nolan wrote:
> On Fri, Apr 25, 2014 at 9:26 PM, Luke-Jr <luke@dashjr.org
> <mailto:luke@dashjr.org>> wrote:
> 
>     They define standard for interoperability between
>     software. So, if you want nodes to relay these transactions, you need to
>     convince them, not merely write a BIP for the transaction format.
> 
> 
> I agree with you in theory, each miner could decide their inclusion
> rules for themselves.
> 
> In practice, if the reference client is updated, then most miners will
> accept those transactions.  In addition, it would eventually propagate
> to alt-coins (or at least the supported ones).
> 
> I could simply submit the changes as a pull request for the reference
> client, but I was hoping that by doing it this way, it would increase
> the odds of it being accepted.
>  
> 
>     Defining a BIP for cross-chain trading would be one way to do that.
> 
> 
> I don't think it quite requires the same coordination in the short
> term.  I could write up the sequence as an info BIP.
> 
>     The malleability "issue" has been known for years.
>     I wouldn't expect any special effort made to fix it...
> 
> 
> It is possible to tweak the protocol so that it still works.  However,
> it means that 3rd parties are required (that could go in the BIP too).
>  
> 
>     There is some ongoing discussion of a softfork to basically redo the
>     Script
>     language entirely, but it will take quite a bit of time and
>     development before
>     we'll see it in the wild.
> 
> 
> Implementing multi-P2SH gets a lot of the benefits of MAST, in terms of
> efficiency.
>  
> 
> 
>     Luke
> 
>     P.S. Did the BIP editor assign these numbers? If not, best to keep them
>     numberless until assigned, to avoid confusion when people Google the
>     real BIP
>     44 and 45...
> 
> 
> Not yet, but that is just my personal repo.  I did email gmaxwell, but
> he said that they can't be assigned until some discussion has happened.
>  
> I take your point that the name appears in the link though, so could
> cause issues with searching.
> 
> 
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> 
> 
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