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From: Stephane Brossier <stephane@kill-bill.org>
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To: Mike Hearn <mike@plan99.net>
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Cc: Pierre-Alexandre Meyer <pierre@kill-bill.org>,
	Bitcoin Dev <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] Extension for BIP-0070 to support
	recurring payments
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--Apple-Mail=_7D5FC4DB-08FD-469A-90F9-DACB05381773
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Mike,


Just want to follow up with you and the community in general regarding =
the BIP0070 extension for recurring billing. At this point we have a =
working prototype that we checked-in in our fork of bitcoinj =
(https://github.com/killbill/bitcoinj). We tested it by extending the =
php 'payment server' from Gavin which we also check-in in a fork =
(https://github.com/killbill/paymentrequest). I think it does not make =
much sense from our side to invest more efforts until we hear some =
feedbacks.

Once we agree/integrate any feedbacks you guys may have-- a proposal for =
next steps would be:
* Turn that into a actual BIP so as to detail how that works,=20
* Write some more serious unit tests
* Merge back code into bitconj trunk

Down the line write the C++ code, but of course that would assume =
BIP0070 is also implemented in C++ as we rely on it.

I understand you guys may have more important matters to solve these =
days with the recent malleability issue, but i want to make it clear =
that we are waiting for feedbacks to make additional progress.

Thanks!

S.




On Feb 14, 2014, at 12:28 PM, Stephane Brossier <stephane@kill-bill.org> =
wrote:

> Kevin,
>=20
> We did a second iteration on the prototype to implement subscription =
cancellation and upgrade/downgrade. We checked in both the bitcoinj and =
php server to be able to test it.
> We also worked on our side of the merchant implementation (Kill Bill) =
to feel confident that the protocol will support advanced business =
cases. At this point it is looking promising, but more work is needed to =
conclude.
>=20
> We wanted to follow up on a few pervious points you raised:
>=20
> > However, continuing to think about this even more, maybe the simple =
memo field along with an empty set of outputs is enough already.
>=20
> =46rom our merchant side (Kill Bill), we do indeed use this field to =
report successes or errors. Maybe it would be useful to extend =
PaymentACK with a boolean success field (so the wallet doesn't commit =
the transaction in case of failures)?
>=20
> > One high-level comment -- the wallet in this design doesn't have any =
way of knowing when the payments are supposed to end. I feel this is =
important to show to the user before they start their wallet polling =
infinitely.
>=20
> We extended our RecurringPaymentDetails message to support this use =
case, as it solves the problem of subscription changes and cancellations =
for free.
>=20
> We introduced the concept of a subscription, referred to by a unique =
id (the tuple merchant_id,subscription_id should be globally unique), =
which has multiple contracts (RecurringPaymentContract). Besides payment =
bounds, each contract has a validity period: generally, a subscription =
will have a unique active contract at a given time and potentially one =
or more pending ones.
>=20
> For example, say you are on the gold plan (1 BTC/mo.) and want to =
downgrade to a bronze plan (0.5 BTC/mo.) at your next billing date. =
Wshen you click "Downgrade" on the merchant site, you will update your =
wallet with two contracts: the current valid one until your next billing =
date (for up to 1 BTC), and a pending one, starting at your next billing =
date (for up to 0.5 BTC/mo. and without an ending date).
> Upon cancellation of the bronze plan, the end date of the contract =
will be updated and polling will stop eventually.
>=20
> All of this contract metadata is returned to the wallet so the user =
can make an informed decision.
>=20
>=20
> Thanks for your feedbacks!
>=20
> S.
>=20
>=20
> On Feb 11, 2014, at 10:37 PM, Kevin Greene <kgreenek@gmail.com> wrote:
>=20
>> Sending this again and truncating since apparently the message body =
was too long.
>>=20
>> Thanks for humoring my questions!
>>=20
>> >I think reporting such errors to the wallet would make complete =
sense. However i am not clear why we would a separate url for that?
>>=20
>> Hmm, thinking about this more, adding a simple status_code in =
PaymentRequest would be a much easier way to achieve this. However, =
continuing to think about this even more, maybe the simple memo field =
along with an empty set of outputs is enough already.
>>=20
>> In bitcoinj, right now the code will throw a =
PaymentRequestException.InvalidOutputs exception if the set of outputs =
is empty with a message of "No Outputs". Because of that, there isn't a =
good way to tell the difference between a payment request that had no =
outputs and a payment request that had some invalid output(s).
>>=20
>> Question to everyone:
>> How does bitcoin-qt handle a PaymentRequest with no outputs?
>=20


--Apple-Mail=_7D5FC4DB-08FD-469A-90F9-DACB05381773
Content-Transfer-Encoding: quoted-printable
Content-Type: text/html;
	charset=iso-8859-1

<html><head><meta http-equiv=3D"Content-Type" content=3D"text/html =
charset=3Diso-8859-1"></head><body style=3D"word-wrap: break-word; =
-webkit-nbsp-mode: space; -webkit-line-break: after-white-space; =
">Mike,<div><br></div><div><br></div><div>Just want to follow up with =
you and the community in general regarding the BIP0070 extension for =
recurring billing. At this point we have a working prototype that we =
checked-in in our fork of bitcoinj (<a =
href=3D"https://github.com/killbill/bitcoinj">https://github.com/killbill/=
bitcoinj</a>). We tested it by extending the php 'payment server' from =
Gavin which we also check-in in a fork (<a =
href=3D"https://github.com/killbill/paymentrequest">https://github.com/kil=
lbill/paymentrequest</a>). I think it does not make much sense from our =
side to invest more efforts until we hear some =
feedbacks.</div><div><br></div><div>Once we agree/integrate any =
feedbacks you guys may have-- a proposal for next steps would =
be:</div><div>*&nbsp;Turn that into a actual BIP so as to detail how =
that works,&nbsp;</div><div>* Write some more serious unit =
tests</div><div>* Merge back code into bitconj =
trunk</div><div><br></div><div>Down the line write the C++ code, but of =
course that would assume BIP0070 is also implemented in C++ as we rely =
on it.</div><div><br></div><div>I understand you guys may have more =
important matters to solve these days with the recent malleability =
issue, but i want to make it clear that we are waiting for feedbacks to =
make additional =
progress.</div><div><br></div><div>Thanks!</div><div><br></div><div>S.</di=
v><div><br></div><div><br></div><div><br></div><div><br></div><div><div><d=
iv>On Feb 14, 2014, at 12:28 PM, Stephane Brossier &lt;<a =
href=3D"mailto:stephane@kill-bill.org">stephane@kill-bill.org</a>&gt; =
wrote:</div><br class=3D"Apple-interchange-newline"><blockquote =
type=3D"cite"><meta http-equiv=3D"Content-Type" content=3D"text/html =
charset=3Diso-8859-1"><div style=3D"word-wrap: break-word; =
-webkit-nbsp-mode: space; -webkit-line-break: after-white-space; =
"><div>Kevin,</div><div><br></div><div>We did a second iteration on the =
prototype to implement subscription cancellation and upgrade/downgrade. =
We checked in both the bitcoinj and php server to be able to test =
it.</div><div>We also worked on our side of the merchant implementation =
(Kill Bill) to feel confident that the protocol will support advanced =
business cases. At this point it is looking promising, but more work is =
needed to conclude.</div><div><br></div><div>We wanted to follow up on a =
few pervious points you raised:</div><div><br></div><div><div>&gt; =
However, continuing to think about this even more, maybe the simple memo =
field along with an empty set of outputs is enough =
already.</div><div><br></div><div>=46rom our merchant side (Kill Bill), =
we do indeed use this field to report successes or errors. Maybe it =
would be useful to extend PaymentACK with a boolean success field (so =
the wallet doesn't commit the transaction in case of =
failures)?</div><div><br></div><div>&gt; One high-level comment -- the =
wallet in this design doesn't have any way of knowing when the payments =
are supposed to end. I feel this is important to show to the user before =
they start their wallet polling infinitely.</div><div><br></div><div>We =
extended our RecurringPaymentDetails message to support this use case, =
as it solves the problem of subscription changes and cancellations for =
free.</div><div><br></div><div>We introduced the concept of a =
subscription, referred to by a unique id (the tuple =
merchant_id,subscription_id should be globally unique), which has =
multiple contracts (RecurringPaymentContract). Besides payment bounds, =
each contract has a validity period: generally, a subscription will have =
a unique active contract at a given time and potentially one or more =
pending ones.</div><div><br></div><div>For example, say you are on the =
gold plan (1 BTC/mo.) and want to downgrade to a bronze plan (0.5 =
BTC/mo.) at your next billing date. Wshen you click "Downgrade" on the =
merchant site, you will update your wallet with two contracts: the =
current valid one until your next billing date (for up to 1 BTC), and a =
pending one, starting at your next billing date (for up to 0.5 BTC/mo. =
and without an ending date).</div><div>Upon cancellation of the bronze =
plan, the end date of the contract will be updated and polling will stop =
eventually.</div><div><br></div><div>All of this contract metadata is =
returned to the wallet so the user can make an informed =
decision.</div></div><div><br></div><div><br></div><div>Thanks for your =
feedbacks!</div><div><br></div><div>S.</div><div><br></div><div><br></div>=
<div><div>On Feb 11, 2014, at 10:37 PM, Kevin Greene &lt;<a =
href=3D"mailto:kgreenek@gmail.com">kgreenek@gmail.com</a>&gt; =
wrote:</div><br class=3D"Apple-interchange-newline"><blockquote =
type=3D"cite"><div dir=3D"ltr"><div class=3D"gmail_default" =
style=3D"color:rgb(51,102,102)">Sending this again and truncating since =
apparently the message body was too long.</div><div =
class=3D"gmail_default" style=3D"color:rgb(51,102,102)"><br></div>

<div class=3D"gmail_default" style=3D"color:rgb(51,102,102)"><div =
class=3D"gmail_default" =
style=3D"font-family:arial,sans-serif;font-size:13px">Thanks for =
humoring my questions!</div><div class=3D"im" =
style=3D"font-family:arial,sans-serif;font-size:13px">

<div class=3D"gmail_default" style=3D"color:rgb(51,102,102)"><span =
style=3D"color:rgb(34,34,34)"><br></span></div><div =
class=3D"gmail_default" style=3D"color:rgb(51,102,102)"><span =
style=3D"color:rgb(34,34,34)">&gt;I think reporting such errors to the =
wallet would make complete sense. However i am not clear why we would a =
separate url for that?</span><br>

</div><div class=3D"gmail_default" =
style=3D"color:rgb(51,102,102)"><br></div></div><div =
class=3D"gmail_default" =
style=3D"font-family:arial,sans-serif;font-size:13px">Hmm, thinking =
about this more, adding a simple status_code in PaymentRequest would be =
a much easier way to achieve this. However, continuing to think about =
this even more, maybe the simple memo field along with an empty set of =
outputs is enough already.</div>

<div class=3D"gmail_default" =
style=3D"font-family:arial,sans-serif;font-size:13px"><br></div><div =
class=3D"gmail_default" =
style=3D"font-family:arial,sans-serif;font-size:13px">In bitcoinj, right =
now the code will throw a PaymentRequestException.InvalidOutputs =
exception if the set of outputs is empty with a message of "No Outputs". =
Because of that, there isn't a good way to tell the difference between a =
payment request that had no outputs and a payment request that had some =
invalid output(s).</div>

<div class=3D"gmail_default" =
style=3D"font-family:arial,sans-serif;font-size:13px"><br></div><div =
class=3D"gmail_default" =
style=3D"font-family:arial,sans-serif;font-size:13px"><b>Question to =
everyone:</b></div><div class=3D"gmail_default" =
style=3D"font-family:arial,sans-serif;font-size:13px">

How does bitcoin-qt handle a PaymentRequest with no =
outputs?</div></div></div>
</blockquote></div><br></div></blockquote></div><br></div></body></html>=

--Apple-Mail=_7D5FC4DB-08FD-469A-90F9-DACB05381773--