[bitcoin-dev] [BIP Draft] Allow zero value OP_RETURN in Payment Protocol

[bitcoin-dev] [BIP Draft] Allow zero value OP_RETURN in Payment Protocol

[Toby Padilla]

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Hi all,

I'm submitting a new BIP draft for consideration and discussion. I've put a
pull request up on Github that implements this BIP (with discussion from
the Core team):

https://github.com/bitcoin/bitcoin/pull/7376

My original discussion of this issue:

https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2015-December/011874.html

BIP draft as follows...

--

```
Title: Allow zero value OP_RETURN in Payment Protocol
Author: Toby Padilla <tobypadilla@gmail.com>
```

## Abstract

This BIP alters the Payment Protocol to allow for zero value OP_RETURN
outputs in serialized PaymentRequests.

## Motivation

The Payment Protocol (defined in BIP70) gives merchants a way to build
sophisticated transactions by serializing one or more outputs in the form
of a PaymentRequest. The PaymentRequest is then served over http/https to a
customer's wallet where the serialized transaction can be executed.

While the Payment Protocol allows for any valid script in its outputs, it
also ignores outputs with zero value. This means BIP70 implementations can
encode an OP_RETURN script but must provide a greater than dust value for
that output. The end result is a successful PaymentRequest transaction with
an OP_RETURN but the value assigned to that output is lost forever.

This BIP allows for zero value OP_RETURN outputs in serialized
PaymentRequests. The change means that OP_RETURN scripts will work as they
were originally intended from within PaymentRequests without permanently
destroying Bitcoin value. Zero value non-OP_RETURN scripts should continue
to be ignored and positive value OP_RETURN outputs should now be rejected.

In addition to fixing the issue of destroyed value, this change opens up
new use cases that were previously impossible.

While storing data on the blockchain is controversial, when used
responsibly OP_RETURN provides a powerful mechanism for attaching metadata
to a transaction. This BIP effectively decouples the creation of
transactions containing OP_RETURN data from the execution of those
transactions. The result are positive benefits for both merchants and
wallets/customers.

By supporting this BIP, wallets can participate in current and future,
unforeseen use cases that benefit from metadata stored in OP_RETURN. Until
now OP_RETURN transactions have typically been created and submitted by
custom software. If a wallet can process a PaymentRequest with OP_RETURN
data as proposed by this BIP, it will support potentially sophisticated
Bitcoin applications without the wallet developer having to have prior
knowledge of that application.

An example might be a merchant that adds the hash of a plain text invoice
to the checkout transaction. The merchant could construct the
PaymentRequest with the invoice hash in an OP_RETURN and pass it to the
customer's wallet. The wallet could then submit the transaction, including
the invoice hash from the PaymentRequest. The wallet will have encoded a
proof of purchase to the blockchain without the wallet developer having to
coordinate with the merchant software or add features beyond this BIP.

Merchants and Bitcoin application developers benefit from this BIP because
they can now construct transactions that include OP_RETURN data in a
keyless environment. Again, prior to this BIP, transactions that used
OP_RETURN (with zero value) needed to be constructed and executed in the
same software. By separating the two concerns, this BIP allows merchant
software to create transactions with OP_RETURN metadata on a server without
storing public or private Bitcoin keys. This greatly enhances security
where OP_RETURN applications currently need access to a private key to sign
transactions.

## Specification

The specification for this BIP is straightforward. BIP70 should be fully
implemented with two changes:

1. Outputs where the script is an OP_RETURN and the value is zero should be
accepted by the wallet.
2. Outputs where the script is an OP_RETURN and the value is greater than
zero should be rejected.

This is a change from the BIP70 requirement that all zero value outputs be
ignored.

## Rationale

As with the discussion around vanilla OP_RETURN, the practice of storing
data on the blockchain is controversial. While blockchain and network bloat
is an undeniable issue, the benefits that come from attaching metadata to
transactions has proven to be too powerful to dismiss entirely. In the
absence of OP_RETURN support the Bitcoin ecosystem has seen alternative,
less elegant and more wasteful methods employed for Blockchain data storage.

As it exists today, BIP70 allows for OP_RETURN data storage at the expense
of permanently destroyed Bitcoin. Even fully removing support for OP_RETURN
values in the Payment Protocol would still leave the door open to
suboptimal data encoding via burning a larger than dust value to an output
with a false address designed to encode data.

This BIP offers all of the same benefits that come from the OP_RETURN
compromise. Mainly that OP_RETURN scripts are provably unspendable and thus
can be pruned from the UTXO pool. Without supporting this BIP, wallets that
support BIP70 will allow for wasteful data storage.

## Compatibility

While not in widespread use, existing BIP70 PaymentRequest outputs that
have a greater than zero value with an OP_RETURN script (burning Bitcoin)
will need to have their values changed to zero or they will be rejected by
wallets implementing this BIP.

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Re: [bitcoin-dev] [BIP Draft] Allow zero value OP_RETURN in Payment Protocol

[Luke Dashjr]

This is a bad idea. OP_RETURN attachments are tolerated (not encouraged!) for 
the sake of the network, since the spam cannot be outright stopped. If it 
could be outright stopped, it would not be reasonable to allow OP_RETURN. When 
it comes to the payment protocol, however, changing the current behaviour has 
literally no benefit to the network at all, and the changes proposed herein 
are clearly detrimental since it would both encourage spam, and potentially 
make users unwilling (maybe even unaware) participants in it. For these 
reasons, *I highly advise against publishing or implementing this BIP, even if 
the later mentioned issues are fixed.*

On Tuesday, January 26, 2016 1:02:44 AM Toby Padilla wrote:
> An example might be a merchant that adds the hash of a plain text invoice
> to the checkout transaction. The merchant could construct the
> PaymentRequest with the invoice hash in an OP_RETURN and pass it to the
> customer's wallet. The wallet could then submit the transaction, including
> the invoice hash from the PaymentRequest. The wallet will have encoded a
> proof of purchase to the blockchain without the wallet developer having to
> coordinate with the merchant software or add features beyond this BIP.

Such a "proof" is useless without wallet support. Even if you argue it could 
be implemented later on, it stands to reason that a scammer will simply encode 
garbage if the wallet is not checking the proof-of-purchase upfront. To check 
it, you would also need further protocol extensions which are not included in 
this draft.

> Merchants and Bitcoin application developers benefit from this BIP because
> they can now construct transactions that include OP_RETURN data in a
> keyless environment. Again, prior to this BIP, transactions that used
> OP_RETURN (with zero value) needed to be constructed and executed in the
> same software. By separating the two concerns, this BIP allows merchant
> software to create transactions with OP_RETURN metadata on a server without
> storing public or private Bitcoin keys. This greatly enhances security
> where OP_RETURN applications currently need access to a private key to sign
> transactions.

I don't see how this has any relevance to keys at all...

> ## Specification
> 
> The specification for this BIP is straightforward. BIP70 should be fully
> implemented with two changes:
> 
> 1. Outputs where the script is an OP_RETURN and the value is zero should be
> accepted by the wallet.
> 2. Outputs where the script is an OP_RETURN and the value is greater than
> zero should be rejected.
> 
> This is a change from the BIP70 requirement that all zero value outputs be
> ignored.

This does not appear to be backward nor even forward compatible. Old clients 
will continue to use the previous behaviour and transparently omit any 
commitments. New clients on the other hand will fail to include commitments 
produced by old servers. In other words, it is impossible to produce software 
compatible with both BIP 70 and this draft, and implementing either would 
result in severe consequences.

> As it exists today, BIP70 allows for OP_RETURN data storage at the expense
> of permanently destroyed Bitcoin.

It is better for the spammers to lose burned bitcoins, than have a way to 
avoid them.

Luke

Re: [bitcoin-dev] [BIP Draft] Allow zero value OP_RETURN in Payment Protocol

[Toby Padilla]

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It looks like my draft hasn't been approved by the mailing list so if
anyone would like to read it it's also on Gist:

https://gist.github.com/toby/9e71811d387923a71a53

Luke - As stated in the Github thread, I totally understand where you're
coming from but the fact is people *will* encode data on the blockchain
using worse methods. For all of the reasons that OP_RETURN was a good idea
in the first place, it's a good idea to support it in PaymentRequests.

As for keyless - there's no way (that I know of) to construct a transaction
with a zero value OP_RETURN in an environment without keys since the
Payment Protocol is what defines the method for getting a transaction from
a server to a wallet. You can make a custom transaction and execute it in
the same application but without Payments there's no way to move
transactions between two applications. You need to build the transaction
where you execute it and thus need a key.



On Mon, Jan 25, 2016 at 6:24 PM, Luke Dashjr <luke@dashjr.org> wrote:

> This is a bad idea. OP_RETURN attachments are tolerated (not encouraged!)
> for
> the sake of the network, since the spam cannot be outright stopped. If it
> could be outright stopped, it would not be reasonable to allow OP_RETURN.
> When
> it comes to the payment protocol, however, changing the current behaviour
> has
> literally no benefit to the network at all, and the changes proposed herein
> are clearly detrimental since it would both encourage spam, and potentially
> make users unwilling (maybe even unaware) participants in it. For these
> reasons, *I highly advise against publishing or implementing this BIP,
> even if
> the later mentioned issues are fixed.*
>
> On Tuesday, January 26, 2016 1:02:44 AM Toby Padilla wrote:
> > An example might be a merchant that adds the hash of a plain text invoice
> > to the checkout transaction. The merchant could construct the
> > PaymentRequest with the invoice hash in an OP_RETURN and pass it to the
> > customer's wallet. The wallet could then submit the transaction,
> including
> > the invoice hash from the PaymentRequest. The wallet will have encoded a
> > proof of purchase to the blockchain without the wallet developer having
> to
> > coordinate with the merchant software or add features beyond this BIP.
>
> Such a "proof" is useless without wallet support. Even if you argue it
> could
> be implemented later on, it stands to reason that a scammer will simply
> encode
> garbage if the wallet is not checking the proof-of-purchase upfront. To
> check
> it, you would also need further protocol extensions which are not included
> in
> this draft.
>
> > Merchants and Bitcoin application developers benefit from this BIP
> because
> > they can now construct transactions that include OP_RETURN data in a
> > keyless environment. Again, prior to this BIP, transactions that used
> > OP_RETURN (with zero value) needed to be constructed and executed in the
> > same software. By separating the two concerns, this BIP allows merchant
> > software to create transactions with OP_RETURN metadata on a server
> without
> > storing public or private Bitcoin keys. This greatly enhances security
> > where OP_RETURN applications currently need access to a private key to
> sign
> > transactions.
>
> I don't see how this has any relevance to keys at all...
>
> > ## Specification
> >
> > The specification for this BIP is straightforward. BIP70 should be fully
> > implemented with two changes:
> >
> > 1. Outputs where the script is an OP_RETURN and the value is zero should
> be
> > accepted by the wallet.
> > 2. Outputs where the script is an OP_RETURN and the value is greater than
> > zero should be rejected.
> >
> > This is a change from the BIP70 requirement that all zero value outputs
> be
> > ignored.
>
> This does not appear to be backward nor even forward compatible. Old
> clients
> will continue to use the previous behaviour and transparently omit any
> commitments. New clients on the other hand will fail to include commitments
> produced by old servers. In other words, it is impossible to produce
> software
> compatible with both BIP 70 and this draft, and implementing either would
> result in severe consequences.
>
> > As it exists today, BIP70 allows for OP_RETURN data storage at the
> expense
> > of permanently destroyed Bitcoin.
>
> It is better for the spammers to lose burned bitcoins, than have a way to
> avoid them.
>
> Luke
>

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Re: [bitcoin-dev] [BIP Draft] Allow zero value OP_RETURN in Payment Protocol

[Luke Dashjr]

On Tuesday, January 26, 2016 2:54:16 AM Toby Padilla wrote:
> Luke - As stated in the Github thread, I totally understand where you're
> coming from but the fact is people *will* encode data on the blockchain
> using worse methods. For all of the reasons that OP_RETURN was a good idea
> in the first place, it's a good idea to support it in PaymentRequests.

As I explained, none of those reasons apply to PaymentRequests.

> As for keyless - there's no way (that I know of) to construct a transaction
> with a zero value OP_RETURN in an environment without keys since the
> Payment Protocol is what defines the method for getting a transaction from
> a server to a wallet. You can make a custom transaction and execute it in
> the same application but without Payments there's no way to move
> transactions between two applications. You need to build the transaction
> where you execute it and thus need a key.

I have no idea what you are trying to say here.

Luke

Re: [bitcoin-dev] [BIP Draft] Allow zero value OP_RETURN in Payment Protocol

[Toby Padilla]

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> As I explained, none of those reasons apply to PaymentRequests.

As they exist today PaymentRequests allow for essentially the same types of
transactions as non-PaymentRequest based transactions with the limitation
that OP_RETURN values must be greater. In that sense they're basically a
pre-OP_RETURN environment. OP_RETURN serves a purpose and it can't be used
with PaymentRequest transactions.

> I have no idea what you are trying to say here.

I think if you think through how you would create an OP_RETURN transaction
today without this BIP you'll see you need a key at some point if you want
a zero value.

On Mon, Jan 25, 2016 at 6:56 PM, Luke Dashjr <luke@dashjr.org> wrote:

> On Tuesday, January 26, 2016 2:54:16 AM Toby Padilla wrote:
> > Luke - As stated in the Github thread, I totally understand where you're
> > coming from but the fact is people *will* encode data on the blockchain
> > using worse methods. For all of the reasons that OP_RETURN was a good
> idea
> > in the first place, it's a good idea to support it in PaymentRequests.
>
> As I explained, none of those reasons apply to PaymentRequests.
>
> > As for keyless - there's no way (that I know of) to construct a
> transaction
> > with a zero value OP_RETURN in an environment without keys since the
> > Payment Protocol is what defines the method for getting a transaction
> from
> > a server to a wallet. You can make a custom transaction and execute it in
> > the same application but without Payments there's no way to move
> > transactions between two applications. You need to build the transaction
> > where you execute it and thus need a key.
>
> I have no idea what you are trying to say here.
>
> Luke
>

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Re: [bitcoin-dev] [BIP Draft] Allow zero value OP_RETURN in Payment Protocol

[Luke Dashjr]

On Tuesday, January 26, 2016 3:01:13 AM Toby Padilla wrote:
> > As I explained, none of those reasons apply to PaymentRequests.
> 
> As they exist today PaymentRequests allow for essentially the same types of
> transactions as non-PaymentRequest based transactions with the limitation
> that OP_RETURN values must be greater. In that sense they're basically a
> pre-OP_RETURN environment. OP_RETURN serves a purpose and it can't be used
> with PaymentRequest transactions.

OP_RETURN can be used, but you need to burn coins. I don't see any benefit to 
changing that. It is better that coins are burned.

> > I have no idea what you are trying to say here.
> 
> I think if you think through how you would create an OP_RETURN transaction
> today without this BIP you'll see you need a key at some point if you want
> a zero value.

You *always* need a key, to redeem inputs... regardless of values.

Luke

Re: [bitcoin-dev] [BIP Draft] Allow zero value OP_RETURN in Payment Protocol

[Toby Padilla]

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> I don't see any benefit to
changing that. It is better that coins are burned.

I think this is our fundamental disagreement. People will burn coins to
encode data, why allow this when there's a better alternative?

> You *always* need a key, to redeem inputs... regardless of values.

Correct, but with BIP70 that key is in the user's wallet and you can
construct transactions on another machine (thus not needing a key during
construction). Right now there's no way to do the transaction construction
on another machine with zero value OP_RETURNs.

On Mon, Jan 25, 2016 at 7:04 PM, Luke Dashjr <luke@dashjr.org> wrote:

> On Tuesday, January 26, 2016 3:01:13 AM Toby Padilla wrote:
> > > As I explained, none of those reasons apply to PaymentRequests.
> >
> > As they exist today PaymentRequests allow for essentially the same types
> of
> > transactions as non-PaymentRequest based transactions with the limitation
> > that OP_RETURN values must be greater. In that sense they're basically a
> > pre-OP_RETURN environment. OP_RETURN serves a purpose and it can't be
> used
> > with PaymentRequest transactions.
>
> OP_RETURN can be used, but you need to burn coins. I don't see any benefit
> to
> changing that. It is better that coins are burned.
>
> > > I have no idea what you are trying to say here.
> >
> > I think if you think through how you would create an OP_RETURN
> transaction
> > today without this BIP you'll see you need a key at some point if you
> want
> > a zero value.
>
> You *always* need a key, to redeem inputs... regardless of values.
>
> Luke
>

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Re: [bitcoin-dev] [BIP Draft] Allow zero value OP_RETURN in Payment Protocol

[Luke Dashjr]

On Tuesday, January 26, 2016 3:07:40 AM Toby Padilla wrote:
> > I don't see any benefit to changing that. It is better that coins are
> > burned.
> 
> I think this is our fundamental disagreement. People will burn coins to
> encode data, why allow this when there's a better alternative?

My point is that there isn't a better alternative. The coins being burned, is 
strictly better than it being gratis.

> > You *always* need a key, to redeem inputs... regardless of values.
> 
> Correct, but with BIP70 that key is in the user's wallet and you can
> construct transactions on another machine (thus not needing a key during
> construction). Right now there's no way to do the transaction construction
> on another machine with zero value OP_RETURNs.

This is also a good thing. Spam should not be made easier or cheaper.

Luke

Re: [bitcoin-dev] [BIP Draft] Allow zero value OP_RETURN in Payment Protocol

[Toby Padilla]

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I don't think every application of OP_RETURN could be classified as "spam".
I also don't think burning the value is going to dissuade anyone from going
down that route. I don't think lost value is better for anyone.

On Mon, Jan 25, 2016 at 7:12 PM, Luke Dashjr <luke@dashjr.org> wrote:

> On Tuesday, January 26, 2016 3:07:40 AM Toby Padilla wrote:
> > > I don't see any benefit to changing that. It is better that coins are
> > > burned.
> >
> > I think this is our fundamental disagreement. People will burn coins to
> > encode data, why allow this when there's a better alternative?
>
> My point is that there isn't a better alternative. The coins being burned,
> is
> strictly better than it being gratis.
>
> > > You *always* need a key, to redeem inputs... regardless of values.
> >
> > Correct, but with BIP70 that key is in the user's wallet and you can
> > construct transactions on another machine (thus not needing a key during
> > construction). Right now there's no way to do the transaction
> construction
> > on another machine with zero value OP_RETURNs.
>
> This is also a good thing. Spam should not be made easier or cheaper.
>
> Luke
>

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Re: [bitcoin-dev] [BIP Draft] Allow zero value OP_RETURN in Payment Protocol

[Luke Dashjr]

On Tuesday, January 26, 2016 3:17:12 AM Toby Padilla wrote:
> I don't think every application of OP_RETURN could be classified as "spam".

Perhaps not, but in this context I cannot think of any non-spam use cases.
Use cases should come before changes to support them.

> I also don't think burning the value is going to dissuade anyone from going
> down that route. I don't think lost value is better for anyone.

Lost value is better because it has a cost to the spammer, and deflates the 
rest of the bitcoins.

Luke

Re: [bitcoin-dev] [BIP Draft] Allow zero value OP_RETURN in Payment Protocol

[Toby Padilla]

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There are already valid use cases for OP_RETURN, it only makes sense to
fully support the feature. The only reason it's not supported now is
because the Payments protocol came before OP_RETURN.

I give one example use case in the BIP. I agree that special wallet support
would make the feature even better, but if someone tried to use Core the
transaction would at least not be rejected.

I've also been exploring this area with key.run (
https://git.playgrub.com/toby/keyrun) and want the functionality for voting
based on aggregate OP_RETURN value. *Not* to store data on the blockchain,
but to associate content pointers with transactions.

I think that since OP_RETURN has already been approved and supported it
doesn't make much sense for me to have to re-defend it from scratch here.

On Mon, Jan 25, 2016 at 7:23 PM, Luke Dashjr <luke@dashjr.org> wrote:

> On Tuesday, January 26, 2016 3:17:12 AM Toby Padilla wrote:
> > I don't think every application of OP_RETURN could be classified as
> "spam".
>
> Perhaps not, but in this context I cannot think of any non-spam use cases.
> Use cases should come before changes to support them.
>
> > I also don't think burning the value is going to dissuade anyone from
> going
> > down that route. I don't think lost value is better for anyone.
>
> Lost value is better because it has a cost to the spammer, and deflates the
> rest of the bitcoins.
>
> Luke
>

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Re: [bitcoin-dev] [BIP Draft] Allow zero value OP_RETURN in Payment Protocol

[Thomas Kerin]

On 26/01/16 03:30, Toby Padilla via bitcoin-dev wrote:
> There are already valid use cases for OP_RETURN, it only makes sense
> to fully support the feature. The only reason it's not supported now
> is because the Payments protocol came before OP_RETURN.
>
You keep saying OP_RETURN is new, but it has been there from day one.
It's purpose is causing script execution to end if encountered.

Since then, we have tolerated putting pushdata's after it, and even
raised the limit for the size of this data. It still doesn't mean every
proposal has to be rewritten to cater for a new allowance we give
OP_RETURN.


> I've also been exploring this area with key.run
> (https://git.playgrub.com/toby/keyrun) and want the functionality for
> voting based on aggregate OP_RETURN value. *Not* to store data on the
> blockchain, but to associate content pointers with transactions.
>
> I think that since OP_RETURN has already been approved and supported
> it doesn't make much sense for me to have to re-defend it from scratch
> here.

I'd generally agree with Luke. Removing the cost of this hurts bitcoin,
and ironically, your application to a certain degree. Just because you
can do a thing one way, it doesn't mean you should. Especially if your
applications success depends on people spamming OP_RETURN hashes of
every torrent they like.

Re: [bitcoin-dev] [BIP Draft] Allow zero value OP_RETURN in Payment Protocol

[Toby Padilla]

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OP_RETURN was not part of isStandard? from day one. Once it was supported
by Core it became necessary to actually support it, not try to support it
in one part of the software and not in others. The whole reason it was
supported is because without it people will use more heinous methods to
encode data on the blockchain. There's no way to stop people from doing
that, so this compromise seemed best for everyone.

I think we should actually define "spam". To me a valid transaction someone
willing pays for is never spam. Also PaymentRequests would be a very
inefficient way to spam. It would be much easier to write a script to
automatically create and submit transactions yourself. With PaymentRequests
 customers have to initiate the transaction and submit/pay for it one by
one.

What is actually the worst case scenario that those opposed to this are
concerned about? That this takes off like wild fire and all of the sudden
millions of people are using PaymentRequests and creating small
transactions? That seems like a win for Bitcoin. It will help spread
support for the Payment protocol and IF it becomes a problem it's because
so many people are using it. In which case there's a very valid use case
for Bitcoin that people are obviously excited about.

I really don't like the idea of policing other people's use of the
protocol. If a transaction pays its fee and has a greater than dust value,
it makes no sense to object to it.

On Tue, Jan 26, 2016 at 8:19 AM, Thomas Kerin via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

>
> On 26/01/16 03:30, Toby Padilla via bitcoin-dev wrote:
> > There are already valid use cases for OP_RETURN, it only makes sense
> > to fully support the feature. The only reason it's not supported now
> > is because the Payments protocol came before OP_RETURN.
> >
> You keep saying OP_RETURN is new, but it has been there from day one.
> It's purpose is causing script execution to end if encountered.
>
> Since then, we have tolerated putting pushdata's after it, and even
> raised the limit for the size of this data. It still doesn't mean every
> proposal has to be rewritten to cater for a new allowance we give
> OP_RETURN.
>
>
> > I've also been exploring this area with key.run
> > (https://git.playgrub.com/toby/keyrun) and want the functionality for
> > voting based on aggregate OP_RETURN value. *Not* to store data on the
> > blockchain, but to associate content pointers with transactions.
> >
> > I think that since OP_RETURN has already been approved and supported
> > it doesn't make much sense for me to have to re-defend it from scratch
> > here.
>
> I'd generally agree with Luke. Removing the cost of this hurts bitcoin,
> and ironically, your application to a certain degree. Just because you
> can do a thing one way, it doesn't mean you should. Especially if your
> applications success depends on people spamming OP_RETURN hashes of
> every torrent they like.
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>

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Re: [bitcoin-dev] [BIP Draft] Allow zero value OP_RETURN in Payment Protocol

[Peter Todd]

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On Tue, Jan 26, 2016 at 09:44:48AM -0800, Toby Padilla via bitcoin-dev wrote:
> I really don't like the idea of policing other people's use of the
> protocol. If a transaction pays its fee and has a greater than dust value,
> it makes no sense to object to it.

I'll point out that getting a BIP for a feature is *not* a hard
requirement for deployment. I'd encourage you to go write up your BIP
document, give it a non-numerical name for ease of reference, and lobby
wallet vendors to implement it.

While I'll refrain from commenting on whether or not I think the feature
itself is a good idea, I really don't want people to get the impression
that we're gatekeepers for how people choose use Bitcoin.

-- 
https://petertodd.org 'peter'[:-1]@petertodd.org
000000000000000008320874843f282f554aa2436290642fcfa81e5a01d78698

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Re: [bitcoin-dev] [BIP Draft] Allow zero value OP_RETURN in Payment Protocol

[Pieter Wuille]

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On Feb 2, 2016 18:04, "Peter Todd via bitcoin-dev" <
bitcoin-dev@lists.linuxfoundation.org> wrote:
>
> On Tue, Jan 26, 2016 at 09:44:48AM -0800, Toby Padilla via bitcoin-dev
wrote:
> > I really don't like the idea of policing other people's use of the
> > protocol. If a transaction pays its fee and has a greater than dust
value,
> > it makes no sense to object to it.
>
> I'll point out that getting a BIP for a feature is *not* a hard
> requirement for deployment. I'd encourage you to go write up your BIP
> document, give it a non-numerical name for ease of reference, and lobby
> wallet vendors to implement it.
>
> While I'll refrain from commenting on whether or not I think the feature
> itself is a good idea, I really don't want people to get the impression
> that we're gatekeepers for how people choose use Bitcoin.

I'll go further: whatever people have commented here and elsewhere about
this feature (myself included) are personal opinions on the feature itself,
in the hope you take the concerns into account.

These comments are not a judgement on whether this should be accepted as a
BIP. Specifically, the BIP editor should accept a BIP even if he personally
dislikes the ideas in it, when the criteria are satisfied.

Beyond that, having a BIP accepted does not mean wallets have to implement
it. That's up to the individual wallet authors/maintainers.

-- 
Pieter

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Re: [bitcoin-dev] [BIP Draft] Allow zero value OP_RETURN in Payment Protocol

[Toby Padilla]

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My BIP was ultimately accepted, it's number 74

https://github.com/bitcoin/bips/blob/master/bip-0074.mediawiki

The editor did not agree with it, and I suspect would comment against it
with his new proposed BIP :)

I really appreciated that despite his vehement disagreement, he assigned
the BIP. It seems like the process worked great. There was deep vetting,
lots of back and forth and the editor put aside his personal opinions to
accept the BIP.

That being said...

The mailing list is a problem. I'm still on moderation only. I have no idea
if this message will go through and when it will go through. I totally
understand the desire to keep the conversation level high, but when people
who *are* whitelisted can quickly post multiple heated arguments against
you (publicly) and you can't respond, then that starts to look very
centralized and discouraging.

I would agree with Gavin on the other thread about the proposed BIP
commenting BIP. Putting more decision power behind a moderated mailing list
and wiki doesn't seem like a good idea.

On Tue, Feb 2, 2016 at 9:16 AM, Pieter Wuille <pieter.wuille@gmail.com>
wrote:

> On Feb 2, 2016 18:04, "Peter Todd via bitcoin-dev" <
> bitcoin-dev@lists.linuxfoundation.org> wrote:
> >
> > On Tue, Jan 26, 2016 at 09:44:48AM -0800, Toby Padilla via bitcoin-dev
> wrote:
> > > I really don't like the idea of policing other people's use of the
> > > protocol. If a transaction pays its fee and has a greater than dust
> value,
> > > it makes no sense to object to it.
> >
> > I'll point out that getting a BIP for a feature is *not* a hard
> > requirement for deployment. I'd encourage you to go write up your BIP
> > document, give it a non-numerical name for ease of reference, and lobby
> > wallet vendors to implement it.
> >
> > While I'll refrain from commenting on whether or not I think the feature
> > itself is a good idea, I really don't want people to get the impression
> > that we're gatekeepers for how people choose use Bitcoin.
>
> I'll go further: whatever people have commented here and elsewhere about
> this feature (myself included) are personal opinions on the feature itself,
> in the hope you take the concerns into account.
>
> These comments are not a judgement on whether this should be accepted as a
> BIP. Specifically, the BIP editor should accept a BIP even if he personally
> dislikes the ideas in it, when the criteria are satisfied.
>
> Beyond that, having a BIP accepted does not mean wallets have to implement
> it. That's up to the individual wallet authors/maintainers.
>
> --
> Pieter
>

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Re: [bitcoin-dev] [BIP Draft] Allow zero value OP_RETURN in Payment Protocol

[Peter Todd]

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On Tue, Feb 02, 2016 at 09:27:58AM -0800, Toby Padilla wrote:
> The mailing list is a problem. I'm still on moderation only. I have no idea
> if this message will go through and when it will go through. I totally
> understand the desire to keep the conversation level high, but when people
> who *are* whitelisted can quickly post multiple heated arguments against
> you (publicly) and you can't respond, then that starts to look very
> centralized and discouraging.

Everyone is on moderation only in this mailing list, myself included.

-- 
https://petertodd.org 'peter'[:-1]@petertodd.org
000000000000000008320874843f282f554aa2436290642fcfa81e5a01d78698

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Re: [bitcoin-dev] [BIP Draft] Allow zero value OP_RETURN in Payment Protocol

[Toby Padilla]

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Then the moderation is being unevenly applied. Luke commented against my
BIP multiple times right after it was published but it took hours for my
responses to go through and I had to track people down on IRC to ask about
it:

http://lists.linuxfoundation.org/pipermail/bitcoin-dev/2016-January/thread.html

On Tue, Feb 2, 2016 at 9:38 AM, Peter Todd <pete@petertodd.org> wrote:

> On Tue, Feb 02, 2016 at 09:27:58AM -0800, Toby Padilla wrote:
> > The mailing list is a problem. I'm still on moderation only. I have no
> idea
> > if this message will go through and when it will go through. I totally
> > understand the desire to keep the conversation level high, but when
> people
> > who *are* whitelisted can quickly post multiple heated arguments against
> > you (publicly) and you can't respond, then that starts to look very
> > centralized and discouraging.
>
> Everyone is on moderation only in this mailing list, myself included.
>
> --
> https://petertodd.org 'peter'[:-1]@petertodd.org
> 000000000000000008320874843f282f554aa2436290642fcfa81e5a01d78698
>

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Re: [bitcoin-dev] [BIP Draft] Allow zero value OP_RETURN in Payment Protocol

[Peter Todd]

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On Tue, Feb 02, 2016 at 09:41:35AM -0800, Toby Padilla wrote:
> Then the moderation is being unevenly applied. Luke commented against my
> BIP multiple times right after it was published but it took hours for my
> responses to go through and I had to track people down on IRC to ask about
> it:
> 
> http://lists.linuxfoundation.org/pipermail/bitcoin-dev/2016-January/thread.html

Keep in mind that actual human beings need to hit the approve button on
your posts; quite likely Luke happened to respond when those humans were
available, and you didn't. I personally had to do the exact same thing
the other day with one of my posts.

Moderation is an unfortunate thing to need, but this list is read by
literally hundreds of busy people, many of whome have had to unsubscribe
at various points in the past due to a lack of moderation. I wish we had
a better solution, but that's what we have. We're also not along in
using fairly agressive moderation, for example the
cryptography@metzdowd.com mailing list where Bitcoin was originally
announced uses manual approval moderation on all messages as well;
there's also an unmoderated offshoot of it, cryptography@randombit.net

(and feel free to start an unmoderated version of bitcoin-dev!)

-- 
https://petertodd.org 'peter'[:-1]@petertodd.org
000000000000000008320874843f282f554aa2436290642fcfa81e5a01d78698

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Re: [bitcoin-dev] [BIP Draft] Allow zero value OP_RETURN in Payment Protocol

[Toby Padilla]

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I think it would be helpful to clarify this in the list documentation.
Right now there's a bunch of conflicting information.

https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev states:

"*Greylisting Notice*
Your first post to this list may be delayed by 5+ minutes due to Greylisting
<https://en.wikipedia.org/wiki/Greylisting>. Subsequent posts should go
through without delay."

https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2015-October/011591.html
states:

"Everyone starts moderated, and the mod bit gets cleared as they post. It
gets set again if someone notices or reports a violation."

On Tue, Feb 2, 2016 at 11:12 AM, Peter Todd <pete@petertodd.org> wrote:

> On Tue, Feb 02, 2016 at 09:41:35AM -0800, Toby Padilla wrote:
> > Then the moderation is being unevenly applied. Luke commented against my
> > BIP multiple times right after it was published but it took hours for my
> > responses to go through and I had to track people down on IRC to ask
> about
> > it:
> >
> >
> http://lists.linuxfoundation.org/pipermail/bitcoin-dev/2016-January/thread.html
>
> Keep in mind that actual human beings need to hit the approve button on
> your posts; quite likely Luke happened to respond when those humans were
> available, and you didn't. I personally had to do the exact same thing
> the other day with one of my posts.
>
> Moderation is an unfortunate thing to need, but this list is read by
> literally hundreds of busy people, many of whome have had to unsubscribe
> at various points in the past due to a lack of moderation. I wish we had
> a better solution, but that's what we have. We're also not along in
> using fairly agressive moderation, for example the
> cryptography@metzdowd.com mailing list where Bitcoin was originally
> announced uses manual approval moderation on all messages as well;
> there's also an unmoderated offshoot of it, cryptography@randombit.net
>
> (and feel free to start an unmoderated version of bitcoin-dev!)
>
> --
> https://petertodd.org 'peter'[:-1]@petertodd.org
> 000000000000000008320874843f282f554aa2436290642fcfa81e5a01d78698
>

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Re: [bitcoin-dev] [BIP Draft] Allow zero value OP_RETURN in Payment Protocol

[Luke Dashjr]

On Tuesday, February 02, 2016 5:16:30 PM Pieter Wuille via bitcoin-dev wrote:
> On Feb 2, 2016 18:04, "Peter Todd via bitcoin-dev" <
> 
> bitcoin-dev@lists.linuxfoundation.org> wrote:
> > On Tue, Jan 26, 2016 at 09:44:48AM -0800, Toby Padilla via bitcoin-dev
> 
> wrote:
> > > I really don't like the idea of policing other people's use of the
> > > protocol. If a transaction pays its fee and has a greater than dust
> 
> value,
> 
> > > it makes no sense to object to it.
> > 
> > I'll point out that getting a BIP for a feature is *not* a hard
> > requirement for deployment. I'd encourage you to go write up your BIP
> > document, give it a non-numerical name for ease of reference, and lobby
> > wallet vendors to implement it.
> > 
> > While I'll refrain from commenting on whether or not I think the feature
> > itself is a good idea, I really don't want people to get the impression
> > that we're gatekeepers for how people choose use Bitcoin.
> 
> I'll go further: whatever people have commented here and elsewhere about
> this feature (myself included) are personal opinions on the feature itself,
> in the hope you take the concerns into account.
> 
> These comments are not a judgement on whether this should be accepted as a
> BIP. Specifically, the BIP editor should accept a BIP even if he personally
> dislikes the ideas in it, when the criteria are satisfied.
> 
> Beyond that, having a BIP accepted does not mean wallets have to implement
> it. That's up to the individual wallet authors/maintainers.

Agree with both Peter and Pieter. Note that BIP 74 was assigned to this 
proposal last Friday.

Luke

Re: [bitcoin-dev] [BIP Draft] Allow zero value OP_RETURN in Payment Protocol

[Andreas Schildbach]

Discussion about reasoning of OP_RETURN aside, I think your
specification needs to be more precise/less ambiguous.

Here is what BIP70 currently says about PaymentDetails.outputs:

"one or more outputs where Bitcoins are to be sent. If the sum of
outputs.amount is zero, the customer will be asked how much to pay, and
the bitcoin client may choose any or all of the Outputs (if there are
more than one) for payment. If the sum of outputs.amount is non-zero,
then the customer will be asked to pay the sum, and the payment shall be
split among the Outputs with non-zero amounts (if there are more than
one; Outputs with zero amounts shall be ignored)."

As you can see, zero outputs are not ignored at all. They are used as an
indication to allow the user to set an amount. So if you'd come up with
one zero-amount OP_RETURN output, it would pop up an amount dialog.
Certainly not what you want, right?


On 01/26/2016 03:54 AM, Toby Padilla via bitcoin-dev wrote:
> It looks like my draft hasn't been approved by the mailing list so if
> anyone would like to read it it's also on Gist:
> 
> https://gist.github.com/toby/9e71811d387923a71a53
> 
> Luke - As stated in the Github thread, I totally understand where you're
> coming from but the fact is people *will* encode data on the blockchain
> using worse methods. For all of the reasons that OP_RETURN was a good
> idea in the first place, it's a good idea to support it in PaymentRequests.
> 
> As for keyless - there's no way (that I know of) to construct a
> transaction with a zero value OP_RETURN in an environment without keys
> since the Payment Protocol is what defines the method for getting a
> transaction from a server to a wallet. You can make a custom transaction
> and execute it in the same application but without Payments there's no
> way to move transactions between two applications. You need to build the
> transaction where you execute it and thus need a key.
> 
> 
> 
> On Mon, Jan 25, 2016 at 6:24 PM, Luke Dashjr <luke@dashjr.org
> <mailto:luke@dashjr.org>> wrote:
> 
>     This is a bad idea. OP_RETURN attachments are tolerated (not
>     encouraged!) for
>     the sake of the network, since the spam cannot be outright stopped.
>     If it
>     could be outright stopped, it would not be reasonable to allow
>     OP_RETURN. When
>     it comes to the payment protocol, however, changing the current
>     behaviour has
>     literally no benefit to the network at all, and the changes proposed
>     herein
>     are clearly detrimental since it would both encourage spam, and
>     potentially
>     make users unwilling (maybe even unaware) participants in it. For these
>     reasons, *I highly advise against publishing or implementing this
>     BIP, even if
>     the later mentioned issues are fixed.*
> 
>     On Tuesday, January 26, 2016 1:02:44 AM Toby Padilla wrote:
>     > An example might be a merchant that adds the hash of a plain text invoice
>     > to the checkout transaction. The merchant could construct the
>     > PaymentRequest with the invoice hash in an OP_RETURN and pass it to the
>     > customer's wallet. The wallet could then submit the transaction, including
>     > the invoice hash from the PaymentRequest. The wallet will have encoded a
>     > proof of purchase to the blockchain without the wallet developer having to
>     > coordinate with the merchant software or add features beyond this BIP.
> 
>     Such a "proof" is useless without wallet support. Even if you argue
>     it could
>     be implemented later on, it stands to reason that a scammer will
>     simply encode
>     garbage if the wallet is not checking the proof-of-purchase upfront.
>     To check
>     it, you would also need further protocol extensions which are not
>     included in
>     this draft.
> 
>     > Merchants and Bitcoin application developers benefit from this BIP because
>     > they can now construct transactions that include OP_RETURN data in a
>     > keyless environment. Again, prior to this BIP, transactions that used
>     > OP_RETURN (with zero value) needed to be constructed and executed in the
>     > same software. By separating the two concerns, this BIP allows merchant
>     > software to create transactions with OP_RETURN metadata on a server without
>     > storing public or private Bitcoin keys. This greatly enhances security
>     > where OP_RETURN applications currently need access to a private key to sign
>     > transactions.
> 
>     I don't see how this has any relevance to keys at all...
> 
>     > ## Specification
>     >
>     > The specification for this BIP is straightforward. BIP70 should be fully
>     > implemented with two changes:
>     >
>     > 1. Outputs where the script is an OP_RETURN and the value is zero should be
>     > accepted by the wallet.
>     > 2. Outputs where the script is an OP_RETURN and the value is greater than
>     > zero should be rejected.
>     >
>     > This is a change from the BIP70 requirement that all zero value outputs be
>     > ignored.
> 
>     This does not appear to be backward nor even forward compatible. Old
>     clients
>     will continue to use the previous behaviour and transparently omit any
>     commitments. New clients on the other hand will fail to include
>     commitments
>     produced by old servers. In other words, it is impossible to produce
>     software
>     compatible with both BIP 70 and this draft, and implementing either
>     would
>     result in severe consequences.
> 
>     > As it exists today, BIP70 allows for OP_RETURN data storage at the expense
>     > of permanently destroyed Bitcoin.
> 
>     It is better for the spammers to lose burned bitcoins, than have a
>     way to
>     avoid them.
> 
>     Luke
> 
> 
> 
> 
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
> 

Re: [bitcoin-dev] [BIP Draft] Allow zero value OP_RETURN in Payment Protocol

[Toby Padilla]

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The wording is a little strange and I think it *should* work as you state,
but Bitcoin Core will actually reject any output that has zero value (even
a single OP_RETURN output -- I just tested again to make sure).

Here's the blocking code:

https://github.com/bitcoin/bitcoin/blob/master/src/qt/paymentserver.cpp#L584

I agree that this should be made more clear in my BIP though, I'll clean up
the language.

On Tue, Jan 26, 2016 at 6:37 AM, Andreas Schildbach via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> Discussion about reasoning of OP_RETURN aside, I think your
> specification needs to be more precise/less ambiguous.
>
> Here is what BIP70 currently says about PaymentDetails.outputs:
>
> "one or more outputs where Bitcoins are to be sent. If the sum of
> outputs.amount is zero, the customer will be asked how much to pay, and
> the bitcoin client may choose any or all of the Outputs (if there are
> more than one) for payment. If the sum of outputs.amount is non-zero,
> then the customer will be asked to pay the sum, and the payment shall be
> split among the Outputs with non-zero amounts (if there are more than
> one; Outputs with zero amounts shall be ignored)."
>
> As you can see, zero outputs are not ignored at all. They are used as an
> indication to allow the user to set an amount. So if you'd come up with
> one zero-amount OP_RETURN output, it would pop up an amount dialog.
> Certainly not what you want, right?
>
>
> On 01/26/2016 03:54 AM, Toby Padilla via bitcoin-dev wrote:
> > It looks like my draft hasn't been approved by the mailing list so if
> > anyone would like to read it it's also on Gist:
> >
> > https://gist.github.com/toby/9e71811d387923a71a53
> >
> > Luke - As stated in the Github thread, I totally understand where you're
> > coming from but the fact is people *will* encode data on the blockchain
> > using worse methods. For all of the reasons that OP_RETURN was a good
> > idea in the first place, it's a good idea to support it in
> PaymentRequests.
> >
> > As for keyless - there's no way (that I know of) to construct a
> > transaction with a zero value OP_RETURN in an environment without keys
> > since the Payment Protocol is what defines the method for getting a
> > transaction from a server to a wallet. You can make a custom transaction
> > and execute it in the same application but without Payments there's no
> > way to move transactions between two applications. You need to build the
> > transaction where you execute it and thus need a key.
> >
> >
> >
> > On Mon, Jan 25, 2016 at 6:24 PM, Luke Dashjr <luke@dashjr.org
> > <mailto:luke@dashjr.org>> wrote:
> >
> >     This is a bad idea. OP_RETURN attachments are tolerated (not
> >     encouraged!) for
> >     the sake of the network, since the spam cannot be outright stopped.
> >     If it
> >     could be outright stopped, it would not be reasonable to allow
> >     OP_RETURN. When
> >     it comes to the payment protocol, however, changing the current
> >     behaviour has
> >     literally no benefit to the network at all, and the changes proposed
> >     herein
> >     are clearly detrimental since it would both encourage spam, and
> >     potentially
> >     make users unwilling (maybe even unaware) participants in it. For
> these
> >     reasons, *I highly advise against publishing or implementing this
> >     BIP, even if
> >     the later mentioned issues are fixed.*
> >
> >     On Tuesday, January 26, 2016 1:02:44 AM Toby Padilla wrote:
> >     > An example might be a merchant that adds the hash of a plain text
> invoice
> >     > to the checkout transaction. The merchant could construct the
> >     > PaymentRequest with the invoice hash in an OP_RETURN and pass it
> to the
> >     > customer's wallet. The wallet could then submit the transaction,
> including
> >     > the invoice hash from the PaymentRequest. The wallet will have
> encoded a
> >     > proof of purchase to the blockchain without the wallet developer
> having to
> >     > coordinate with the merchant software or add features beyond this
> BIP.
> >
> >     Such a "proof" is useless without wallet support. Even if you argue
> >     it could
> >     be implemented later on, it stands to reason that a scammer will
> >     simply encode
> >     garbage if the wallet is not checking the proof-of-purchase upfront.
> >     To check
> >     it, you would also need further protocol extensions which are not
> >     included in
> >     this draft.
> >
> >     > Merchants and Bitcoin application developers benefit from this BIP
> because
> >     > they can now construct transactions that include OP_RETURN data in
> a
> >     > keyless environment. Again, prior to this BIP, transactions that
> used
> >     > OP_RETURN (with zero value) needed to be constructed and executed
> in the
> >     > same software. By separating the two concerns, this BIP allows
> merchant
> >     > software to create transactions with OP_RETURN metadata on a
> server without
> >     > storing public or private Bitcoin keys. This greatly enhances
> security
> >     > where OP_RETURN applications currently need access to a private
> key to sign
> >     > transactions.
> >
> >     I don't see how this has any relevance to keys at all...
> >
> >     > ## Specification
> >     >
> >     > The specification for this BIP is straightforward. BIP70 should be
> fully
> >     > implemented with two changes:
> >     >
> >     > 1. Outputs where the script is an OP_RETURN and the value is zero
> should be
> >     > accepted by the wallet.
> >     > 2. Outputs where the script is an OP_RETURN and the value is
> greater than
> >     > zero should be rejected.
> >     >
> >     > This is a change from the BIP70 requirement that all zero value
> outputs be
> >     > ignored.
> >
> >     This does not appear to be backward nor even forward compatible. Old
> >     clients
> >     will continue to use the previous behaviour and transparently omit
> any
> >     commitments. New clients on the other hand will fail to include
> >     commitments
> >     produced by old servers. In other words, it is impossible to produce
> >     software
> >     compatible with both BIP 70 and this draft, and implementing either
> >     would
> >     result in severe consequences.
> >
> >     > As it exists today, BIP70 allows for OP_RETURN data storage at the
> expense
> >     > of permanently destroyed Bitcoin.
> >
> >     It is better for the spammers to lose burned bitcoins, than have a
> >     way to
> >     avoid them.
> >
> >     Luke
> >
> >
> >
> >
> > _______________________________________________
> > bitcoin-dev mailing list
> > bitcoin-dev@lists.linuxfoundation.org
> > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
> >
>
>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>

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Re: [bitcoin-dev] [BIP Draft] Allow zero value OP_RETURN in Payment Protocol

[Peter Todd]

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On Tue, Jan 26, 2016 at 09:41:01AM -0800, Toby Padilla via bitcoin-dev wrote:
> The wording is a little strange and I think it *should* work as you state,
> but Bitcoin Core will actually reject any output that has zero value (even
> a single OP_RETURN output -- I just tested again to make sure).
> 
> Here's the blocking code:
> 
> https://github.com/bitcoin/bitcoin/blob/master/src/qt/paymentserver.cpp#L584
> 
> I agree that this should be made more clear in my BIP though, I'll clean up
> the language.

Note that because the dust limit is ignored completely for OP_RETURN
outputs, you can work around this by setting the OP_RETURN outputs to 1
satoshi instead.

-- 
https://petertodd.org 'peter'[:-1]@petertodd.org
000000000000000008320874843f282f554aa2436290642fcfa81e5a01d78698

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