Received: from sog-mx-4.v43.ch3.sourceforge.com ([172.29.43.194] helo=mx.sourceforge.net) by sfs-ml-3.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1WIN3Y-00075V-SP for bitcoin-development@lists.sourceforge.net; Tue, 25 Feb 2014 18:48:40 +0000 Received-SPF: pass (sog-mx-4.v43.ch3.sourceforge.com: domain of zikula.org designates 74.125.82.44 as permitted sender) client-ip=74.125.82.44; envelope-from=drak@zikula.org; helo=mail-wg0-f44.google.com; Received: from mail-wg0-f44.google.com ([74.125.82.44]) by sog-mx-4.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1WIN3X-00064k-2q for bitcoin-development@lists.sourceforge.net; Tue, 25 Feb 2014 18:48:40 +0000 Received: by mail-wg0-f44.google.com with SMTP id a1so770386wgh.3 for ; Tue, 25 Feb 2014 10:48:32 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc:content-type; bh=LLPbMEH6OzC3CHEU2oeiQDFPme9msH+YbBw+RqRpsiQ=; b=Y6p41A/PF2wnoIukOj6Kdhw/Q1AJnETJnYQTMqiGbRxbiCek0YrkxO4VQsA5Ufjy6j zMgVqGpOxPI2ZL5kYGkqTtRf4uujS2dXV7c1maI+VIM4qI5HG0XGvTDjmwffnWUOoVgP m1vTBvMuefftmXyYHD+4D1eJ21ZfJiKZ1M7uXVfFTG1Yh7Za6IEDeBN9mzS+tlvifWL6 4T0dN2MWv/Qbkts7QG7wuP8neW/I7mIS4Wc4YIc8vzkHR/8pWtPzWgcLDWZPIAqfKXM1 ahwkkF1LqKbxIVO+E1+UChKTwETlWHwh6psNR+MmC5dqPQW4nK4tCSX5qIbHVLb7U3iC 7x3g== X-Gm-Message-State: ALoCoQnRwczXf9nEZidlEcIY1JV6GQx1ASd4S2f+IZAiMArs2N82Ax1ym1BeWYKwiZ1wHBk6hokr X-Received: by 10.194.61.210 with SMTP id s18mr26248406wjr.10.1393353623527; Tue, 25 Feb 2014 10:40:23 -0800 (PST) MIME-Version: 1.0 Received: by 10.194.205.69 with HTTP; Tue, 25 Feb 2014 10:40:03 -0800 (PST) In-Reply-To: References: <0CC0BE1D-1DAA-4994-B034-EB7712F845CF@kill-bill.org> <5F91BEBF-ECDD-4CBD-A85E-FD7E7DB3F01F@kill-bill.org> <81FBEA67-45A9-4531-BEA0-071CE9FAEF7E@kill-bill.org> From: Drak Date: Tue, 25 Feb 2014 18:40:03 +0000 Message-ID: To: Mike Hearn Content-Type: multipart/alternative; boundary=047d7b86d586c6f79704f33f6b48 X-Spam-Score: -0.5 (/) X-Spam-Report: Spam Filtering performed by mx.sourceforge.net. See http://spamassassin.org/tag/ for more details. -1.5 SPF_CHECK_PASS SPF reports sender host as permitted sender for sender-domain -0.0 SPF_PASS SPF: sender matches SPF record 1.0 HTML_MESSAGE BODY: HTML included in message X-Headers-End: 1WIN3X-00064k-2q Cc: Bitcoin Dev , Stephane Brossier , Pierre-Alexandre Meyer Subject: Re: [Bitcoin-development] Extension for BIP-0070 to support recurring payments X-BeenThere: bitcoin-development@lists.sourceforge.net X-Mailman-Version: 2.1.9 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 25 Feb 2014 18:48:41 -0000 --047d7b86d586c6f79704f33f6b48 Content-Type: text/plain; charset=UTF-8 Forgive me if I missed it, but the spec doesnt look like it can handle only handle periods of per week, per month, per quarter rather than 'n period'. I take Paypal as a reference example for subscription payments where you can set recurring to every: n days, n weeks, n months, n years. That way a quarterly payment is every 3 months. This fine granularity is necessary because sometime a payment scheme can be per 4 weekly rather than per monthly. So in summary the spec needs daily as an option, and to specify the recurring cycle as every n*period (one of daily, weekly, monthly, yearly): and you can drop quarterly since it's just expressed as per 3*monthly. Drak On 25 February 2014 16:29, Mike Hearn wrote: > Hey there, > > So the essence of this protocol is as follows: > > enum PaymentFrequencyType { > > WEEKLY = 1; > > MONTHLY = 2; > > QUARTERLY = 3; > > ANNUAL = 4; > } > message RecurringPaymentDetails { > // Namespace for the merchant such as org.foo.bar > > required string merchant_id = 1; > > // Id for the recurring subscription > required bytes subscription_id = 2; > > // Contracts associated with a given subscription > > repeated RecurringPaymentContract contracts = 3; > > } > message RecurringPaymentContract { > > // Unique id for a given contract > > required bytes contract_id = 1; > > // URL to poll to get the next PaymentRequest > > required string polling_url = 2; > > // Timestamp; when this contract starts > required uint64 starts = 3; > > // Timestamp; when this contract should be considered invalid > > optional uint64 ends = 4; > > // Expected payment frequency > optional PaymentFrequencyType payment_frequency_type = 5; > > // Max payment amount within that frequency (e.g. no more than 5 BTC per month) > > optional uint64 max_payment_per_period = 6; > > // Max payment amount (e.g. no more than 3 BTC per payment) > > optional uint64 max_payment_amount = 7; > > } > > I have the following comments: > > 1. There's no need to serialize RecurringPaymentDetails as bytes here. > It's done that way outside of PaymentDetails in order to support digital > signatures over protobufs that may have extensions the wallet app isn't > aware of, but it's a pain and inside PaymentDetails (and therefore for most > extensions) it shouldn't be necessary. So you can just use "optional > RecurringPamentDetails recurring_payments = 8;" > > 2. There's only 4 possibilities here for recurrences. That seems > rather restrictive. Is the cost of being more expressive really so high? > Why not allow more flexible specification of periods? > > 3. If there's no payment_frequency_type field then what happens? A > quirk of protobufs to be aware of is that making an enum field "required" > can hurt backwards compatibility. Because it will be expressed using a > languages underlying enum type, if there's a new enum member added later > old software that attempts to deserialize this will throw exceptions > because the new "unknown" member would be unrepresentable in the old model. > Making the field optional avoids this problem (it will be treated as > missing instead) but means software needs to be written to know what to do > when it can't read the enum value / sees enum values from the future. > > 4. I assume the amounts are specified in terms of satoshi, and > timestamps are UNIX time, but better to make that explicit. > > 5. Seems there's an implicit value constraint that max_payment_amount > <= max_payment_per_period. What happens if that constraint is violated? > Best to document that. > > 6. What's the "merchant ID" namespace thing about? What's it for? What > happens if I set my competitors merchant ID there? > > 7. What's the "subscription ID"? Is this stuff not > duplicative/redundant with the existing merchant_data field? > > 8. In what situations would you have >1 contract per payment request? > I'm not sure I understand why it's repeated. Presumably if there are zero > contracts included the data should be ignored, or an error thrown and the > entire payment request rejected? Which should it be? > > 9. It's unclear to me given such a contract when the payment should > actually occur. For instance if it's "monthly" then what day in the month > would the payment occur? > > 10. You'll notice I moved the comments to be above the field > definitions. I know the current proto isn't done that way, but let's change > it - long comments are good and putting them above the field definitions > encourages people to write enough detail without being put off by line > length constraints > > > I think the next step would be to talk to BitPay/get Jeff+Stephen involved > because I know they have customers that really want recurring payments, and > those guys will have a clearer idea of customer requirements than we do. I > feel uncomfortable with designing or reviewing in a vacuum without some > actual people who would use it chiming in, as I don't really know much > about the underlying business processes. > > I have some other comments about the bitcoinj implementation specifically > - for instance, we don't have a "wallet directory" concept: everything goes > into the wallet file. So we'll need to think about how to structure the > code to allow that. Also, just using a background polling thread is likely > not flexible enough, as on some platforms you can't stay running all the > time (e.g. Android) without upsetting people, but the underlying OS can > wake you up at the right times, so wallet apps should have an ability to > control wakeup tasks. But we can discuss that over on the bitcoinj list > specifically. Let's keep this thread for the general protocol design. > > BIP 70 is indeed implemented in Bitcoin Core on the C++ side, so that > isn't a concern. It could be done there too. > > > > ------------------------------------------------------------------------------ > Flow-based real-time traffic analytics software. Cisco certified tool. > Monitor traffic, SLAs, QoS, Medianet, WAAS etc. with NetFlow Analyzer > Customize your own dashboards, set traffic alerts and generate reports. > Network behavioral analysis & security monitoring. All-in-one tool. > > http://pubads.g.doubleclick.net/gampad/clk?id=126839071&iu=/4140/ostg.clktrk > _______________________________________________ > Bitcoin-development mailing list > Bitcoin-development@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/bitcoin-development > > --047d7b86d586c6f79704f33f6b48 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Forgive me if I missed it, but the spec doesnt look like i= t can handle only handle periods of per week, per month, per quarter rather= than 'n period'. I take Paypal as a reference example for subscrip= tion payments where you can set recurring to every: n days, n weeks, n mont= hs, n years. That way a quarterly payment is every 3 months. This fine gran= ularity is necessary because sometime a payment scheme can be per 4 weekly = rather than per monthly.

So in summary the spec needs daily as an option, and to spec= ify the recurring cycle as every n*period (one of daily, weekly, monthly, y= early): and you can drop quarterly since it's just expressed as per 3*m= onthly.

Drak


On 25 February 2014 16:29, Mike Hearn <mike@plan99.net> wrote:
Hey there,

So the essence of this protocol is as follows:

= 


enum PaymentFrequencyType {

=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
WEEKLY =3D 1;

=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
MONTHLY =3D 2;

=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
QUARTERLY =3D 3;

=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
ANNUAL =3D 4;

}
message RecurringPaymentDetails {


        // Namespace for the merchant such as o=
rg.foo.bar

=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0required string merchant_id =3D 1=
;                 




        // Id for the recurring subscription
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0required bytes subs=
cription_id =3D 2;
// Contracts associated with a given subscription
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0repeated RecurringPaymentContract contracts =3D 3;
}
message RecurringPaymentContract {
// Unique id for a given contract
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0required bytes contract_id =3D 1<= span>;
// URL to poll to get the next PaymentRequest=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0required string polling_url =3D 2= ;
// Timestamp; when this contract starts
=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0required uint64 = starts =3D 3;
// Timestamp; when this contract should be considere= d invalid
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0optional uint64 ends =3D 4;=
// Expected payment frequency
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0optional PaymentFrequencyType payment_frequency_type =3D 5= ;
// Max payment amount within that frequency (e.g. no= more than 5 BTC per month)
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0optional uint64 max_payment_per_period =3D 6;
// Max payment amount (e.g. no more than 3 BTC per p= ayment)
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0optional uint64 max_payment_amount =3D 7= ;
}

<= /div>
I have the following comments:
  1. There's no need to serialize RecurringPaymentDetails as by= tes here. It's done that way outside of PaymentDetails in order to supp= ort digital signatures over protobufs that may have extensions the wallet a= pp isn't aware of, but it's a pain and inside PaymentDetails (and t= herefore for most extensions) it shouldn't be necessary. So you can jus= t use "optional RecurringPamentDetails recurring_payments =3D 8;"=

  2. There's only 4 possibilities here for recurrences. That se= ems rather restrictive. Is the cost of being more expressive really so high= ? Why not allow more flexible specification of periods?

  3. If there's no payment_frequency_type field then what happens? A quirk o= f protobufs to be aware of is that making an enum field "required"= ; can hurt backwards compatibility. Because it will be expressed using a la= nguages underlying enum type, if there's a new enum member added later = old software that attempts to deserialize this will throw exceptions becaus= e the new "unknown" member would be unrepresentable in the old mo= del. Making the field optional avoids this problem (it will be treated as m= issing instead) but means software needs to be written to know what to do w= hen it can't read the enum value / sees enum values from the future.
  4. I assume the amounts are specified in terms of satoshi, and ti= mestamps are UNIX time, but better to make that explicit.

  5. S= eems there's an implicit value constraint that max_payment_amount <= =3D max_payment_per_period. What happens if that constraint is violated? Be= st to document that.

  6. What's the "merchant ID" namespace thing about? = What's it for? What happens if I set my competitors merchant ID there?<= br>
  7. What's the "subscription ID"? Is this stuff n= ot duplicative/redundant with the existing merchant_data field?

  8. In what situations would you have >1 contract per payment r= equest? I'm not sure I understand why it's repeated. Presumably if = there are zero contracts included the data should be ignored, or an error t= hrown and the entire payment request rejected? Which should it be?

  9. It's unclear to me given such a contract when the payment = should actually occur. For instance if it's "monthly" then wh= at day in the month would the payment occur?

  10. You'll not= ice I moved the comments to be above the field definitions. I know the curr= ent proto isn't done that way, but let's change it - long comments = are good and putting them above the field definitions encourages people to = write enough detail without being put off by line length constraints

I think the next step would be to talk to Bi= tPay/get Jeff+Stephen involved because I know they have customers that real= ly want recurring payments, and those guys will have a clearer idea of cust= omer requirements than we do. I feel uncomfortable with designing or review= ing in a vacuum without some actual people who would use it chiming in, as = I don't really know much about the underlying business processes.

I have some other comments about the bitcoinj implement= ation specifically - for instance, we don't have a "wallet directo= ry" concept: everything goes into the wallet file. So we'll need t= o think about how to structure the code to allow that. Also, just using a b= ackground polling thread is likely not flexible enough, as on some platform= s you can't stay running all the time (e.g. Android) without upsetting = people, but the underlying OS can wake you up at the right times, so wallet= apps should have an ability to control wakeup tasks. But we can discuss th= at over on the bitcoinj list specifically. Let's keep this thread for t= he general protocol design.

BIP 70 is indeed implemented in B= itcoin Core on the C++ side, so that isn't a concern. It could be done = there too.


-----------------------------------------------------------------------= -------
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Monitor traffic, SLAs, QoS, Medianet, WAAS etc. with NetFlow Analyzer
Customize your own dashboards, set traffic alerts and generate reports.
Network behavioral analysis & security monitoring. All-in-one tool.
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