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Date: Thu, 05 Feb 2015 18:38:17 -0500
From: Andy Schroder <info@AndySchroder.com>
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Subject: Re: [Bitcoin-development] Two Proposed BIPs - Bluetooth
 Communication and bitcoin: URI Scheme Improvements
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Hello,

With the recent discussion started today regarding another bluetooth=20
communication proposal created by Airbitz, I'd like to bring people's=20
attention back to this proposal that saw little discussion last fall. I=20
guess I'm not sure why two proposals are being created. Is their some=20
advantage of using bluetooth low energy over standard bluetooth (I'm not =

well versed in bluetooth low energy)? This NFC coupled approach seems to =

avoid a lot of issues with identifying the correct payee. You can see=20
this proposed scheme demonstrated in action in a POS application in the=20
video link below which demonstrates it with my fuel pump and Andreas=20
Schildbach's wallet.

There was a small discussion that occurred after my original=20
announcement below. If you are new to this e-mail list, you can find an=20
archive of those few replies here:=20
https://www.mail-archive.com/bitcoin-development%40lists.sourceforge.net/=
msg06354.html

Since this original announcement, a few improvements have been made to=20
the proposal:

 1. Improved documentation and explanation of the use cases in
    Schildbach's wallet's wiki
     1. https://github.com/schildbach/bitcoin-wallet/wiki/Payment-Request=
s
 2. Issue with the payment_url field has resolved by changing to a
    repeated field and requiring the wallet to search for the protocol
    they want to use, rather than expecting it to be a certain element
    number in the list.
     1. https://github.com/AndySchroder/bips/blob/master/tbip-0075.mediaw=
iki


Although there are some interesting use cases of Airbitz's proposal's=20
work flow, tapping an NFC radio with a 5 mm range requires much less=20
brain power and time than picking the correct name on the app's screen.=20
The manual name picking is going to be especially crazy in a very=20
congested location. The payer isn't ever going to want to have to try=20
and figure out what register or payment terminal they are at for most=20
applications I would ever use.

I'd like to see something happen with this technology. I've also noticed =

that micropayment channels have little formality to being established=20
practically and it would be awesome if they could be managed over=20
bluetooth as well. Maybe more improvements to the payment protocol can=20
simultaneously result (and also extended to bluetooth) that embrace the=20
establishment of micropayment channels.


Andy Schroder

On 10/17/2014 03:58 PM, Andy Schroder wrote:
> Hello,
>
> I'd like to introduce two proposed BIPs. They are primarily focused on =

> implementing the payment protocol using bluetooth connections. I've=20
> been working on automated point of sale devices and bluetooth=20
> communication is critical in my mind due to the potential lack of=20
> internet access at many points of sale, either due to lack of cellular =

> internet coverage, lack of payee providing wireless internet, and/or=20
> due to financial constraints of the payer prohibiting them from=20
> maintaining a cellular internet service plan. These BIPs are largely=20
> modeled after the current functionality of Andreas Schildbach's=20
> android Bitcoin Wallet's bluetooth capability. I've discussed the=20
> communication scheme with him in depth and believe these proposals to=20
> clearly and accurately represent the communication scheme.
>
> There is also an additional &h=3D parameter added to the bitcoin: URI=20
> scheme which applies to both bluetooth and http payment protocol=20
> requests which allows for a hash of the payment request to be=20
> included. This hash was proposed by Andreas as an amendment to BIP72,=20
> but others preferred not to amend BIP72 since it has already been put=20
> into place. The current version of Schildbach's bitcoin wallet already =

> supports the "h parameter".
>
> I'd appreciate feedback from everyone, particularly wallet developers=20
> as widespread bluetooth support among wallets is very important to me. =

> I'm also very new to this mailing list as well as the BIP writing=20
> process, so I'd appreciate your understanding if my conventions are=20
> not standard. I am currently using the naming conventions "TBIP", so=20
> that I can propose /temporary/ BIP numbers, and cross reference=20
> between the two. Obviously these will change if the BIPs are formally=20
> adopted. You can find a copy of these proposed BIPs at the following=20
> links:
>
>   * https://github.com/AndySchroder/bips/blob/master/tbip-0074.mediawik=
i
>   * https://github.com/AndySchroder/bips/blob/master/tbip-0075.mediawik=
i
>
>
> If you are interested, you can see a demonstration of many of the=20
> proposed features using Schildbach's wallet and my fuel pump in a=20
> video I recently created: https://youtu.be/kkVAhA75k1Y . The main=20
> thing not implemented is multiple URLs for the payment protocol, so,=20
> as a hack, I'm just presenting https vi QR code and bluetooth via NFC=20
> on my fuel pump for now.
>
>
>
> There are a few known issues that could be improved to this bluetooth=20
> communication scheme as well as the general payment protocol and=20
> myself and Andreas would like to receive feedback regarding concerns=20
> and potential solutions. Some of the known issues are:
>
>   * There may seem to be some inconsistency in the connection header
>     messages between the payment request connection and the payment
>     connection. This is largely because it is how Andreas originally
>     implemented the communication and is hesitant to change it since
>     there are many instances of is software already deployed that
>     implement this scheme.
>   * The current method uses an unauthenticated bluetooth connection
>     for bluetooth 2.1 and newer devices (subject to man in the middle
>     attacks, but not passive eavesdroppers), and an unsecure and
>     unauthenticated connection for older devices. The known concerns
>     here are that someone within 100 meters of the payer could track
>     the bitcoin addresses used for the transaction and could possibly
>     replace the refund address by submitting a forged payment message
>     to the payee. Requiring bluetooth 2.1 and authenticating the
>     connection out of band unfortunately don't seem to be as
>     straightforward/simple of a task with most bluetooth libraries
>     (although I'd love for someone to prove me wrong). It's possible
>     this communication scheme could be extended to use an https "like"
>     protocol that would not care if the underlying bluetooth
>     connection is authenticated or encrypted. It's actually possible
>     that http over a bluetooth socket (instead of tcp socket) could be
>     implemented, however it is presently uncertain whether this would
>     be too slow, too much overhead (both on the devices software and
>     communication), or if http could easily be run over bluetooth
>     sockets on all platforms.
>   * There is no acknowledgement failure message possible in the
>     payment protocol, only an acknowledgement message or lack of
>     acknowledgement message. This issue seems to be a concern and as a
>     result, the memo field is used to send an "ack" or "nack" in
>     Schildbach's wallet. Can we add a boolean status field to the
>     payment acknowledgement message?
>   * I'd personally like a new optional boolean field added to the
>     "PaymentDetails" portion of the "PaymentRequest" to allow for the
>     payer's wallet to match the "Output" optional "amount" fields as a
>     total amount of all Outputs, rather than requiring the amount for
>     each output to be matched exactly. As it currently is, the payee
>     can specify multiple receiving addresses in order to require a
>     payer split up the payments so that when the payee then goes to
>     spend the funds later, they don't necessarily have to give their
>     payees as much knowledge of their balances and spending and
>     receiving habits and sources. As the payment protocol currently is
>     requiring all output amounts to be matched exactly for each
>     output, there is no flexibility given to the payer in order to
>     reduce a merging or unnecessary diverging of account funds, which
>     can reduce the privacy of both the payer and the payee. If the
>     payee were given the option to allow the payer the option to
>     divide the amounts amount the outputs intelligently, there can be
>     some privacy gained.
>   * Amount of data stored in QR codes may be getting large when a
>     backwards compatible URL is used (for wallets that don't support
>     the payment protocol) and can be difficult to scan with outdoor
>     screens that have an extra weather resistant pane when in direct
>     sunlight.
>   * The number of offline transactions of a wallet is limited to the
>     known unspent outputs when they go offline. Long term, I'd like to
>     see wallet devices that can use systems such as Kryptoradio's
>     DVB-T based broadcast (but this will need yet another radio!).
>     Another project may be to develop a blockchain query protocol of
>     some kind where retailers can provide access to blockchain data so
>     that customer's wallets can update their known unspent outputs via
>     bluetooth. It's possible such a bluetooth system could be used in
>     combination of "Kryptoradio" like broadcasts to provide multiple
>     blockchain references.
>   * The additional payment_url approach is a bit sloppy of a solution
>     in the PaymentDetails portion of the PaymentRequest. It would have
>     been ideal to just change this from an optional field to a
>     repeated field, however, the backwards compatibility in the
>     protocol buffer format will provide the last item in the array for
>     a repeated field (to a code that expects it to be an optional
>     field), rather than the first. Because of this, backwards
>     compatibility with https payment requests wouldn't work if the
>     payment_url field is just changed to a repeated field.
>       o Possible alternatives to what is described in the proposed BIP
>           + Change payment_url to a repeated field and then reverse
>             the order of the parameter numbers in the payment_url,
>             compared to the bitcoin URL "r parameter".
>           + Create an additional, new payment_url_multi repeated field
>             (or some better name), and then leave the original
>             payment_url field in there for backwards compatibility
>             (and then maybe phase it out in the future).
>       o Reference
>           + https://developers.google.com/protocol-buffers/docs/proto#u=
pdating
>               # "|optional| is compatible with |repeated|. Given
>                 serialized data of a repeated field as input, clients
>                 that expect this field to be |optional| will take the
>                 last input value if it's a primitive type field or
>                 merge all input elements if it's a message type field."=

>
>
>
> Your comments and suggestions would be greatly appreciated.
>
> --=20
> Andy Schroder
>


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  </head>
  <body bgcolor=3D"#FFFFFF" text=3D"#000000">
    <div class=3D"moz-cite-prefix">Hello,<br>
      <br>
      With the recent discussion started today regarding another
      bluetooth communication proposal created by Airbitz, I'd like to
      bring people's attention back to this proposal that saw little
      discussion last fall. I guess I'm not sure why two proposals are
      being created. Is their some advantage of using bluetooth low
      energy over standard bluetooth (I'm not well versed in bluetooth
      low energy)? This NFC coupled approach seems to avoid a lot of
      issues with identifying the correct payee. You can see this
      proposed scheme demonstrated in action in a POS application in the
      video link below which demonstrates it with my fuel pump and
      Andreas Schildbach's wallet.<br>
      <br>
      There was a small discussion that occurred after my original
      announcement below. If you are new to this e-mail list, you can
      find an archive of those few replies here:
<a class=3D"moz-txt-link-freetext" href=3D"https://www.mail-archive.com/b=
itcoin-development%40lists.sourceforge.net/msg06354.html">https://www.mai=
l-archive.com/bitcoin-development%40lists.sourceforge.net/msg06354.html</=
a><br>
      <br>
      Since this original announcement, a few improvements have been
      made to the proposal:<br>
      <ol>
        <li>Improved documentation and explanation of the use cases in
          Schildbach's wallet's wiki</li>
        <ol>
          <li><a class=3D"moz-txt-link-freetext" href=3D"https://github.c=
om/schildbach/bitcoin-wallet/wiki/Payment-Requests">https://github.com/sc=
hildbach/bitcoin-wallet/wiki/Payment-Requests</a></li>
        </ol>
        <li>Issue with the payment_url field has resolved by changing to
          a repeated field and requiring the wallet to search for the
          protocol they want to use, rather than expecting it to be a
          certain element number in the list.</li>
        <ol>
          <li><a moz-do-not-send=3D"true" class=3D"moz-txt-link-freetext"=

href=3D"https://github.com/AndySchroder/bips/blob/master/tbip-0075.mediaw=
iki">https://github.com/AndySchroder/bips/blob/master/tbip-0075.mediawiki=
</a></li>
        </ol>
      </ol>
      <br>
      Although there are some interesting use cases of Airbitz's
      proposal's work flow, tapping an NFC radio with a 5 mm range
      requires much less brain power and time than picking the correct
      name on the app's screen. The manual name picking is going to be
      especially crazy in a very congested location. The payer isn't
      ever going to want to have to try and figure out what register or
      payment terminal they are at for most applications I would ever
      use.<br>
      <br>
      I'd like to see something happen with this technology. I've also
      noticed that micropayment channels have little formality to being
      established practically and it would be awesome if they could be
      managed over bluetooth as well. Maybe more improvements to the
      payment protocol can simultaneously result (and also extended to
      bluetooth) that embrace the establishment of micropayment
      channels.<br>
      <br>
      <br>
      <br>
      <pre class=3D"moz-signature" cols=3D"72">Andy Schroder</pre>
      On 10/17/2014 03:58 PM, Andy Schroder wrote:<br>
    </div>
    <blockquote cite=3D"mid:544174F8.1050208@AndySchroder.com" type=3D"ci=
te">
      <meta http-equiv=3D"content-type" content=3D"text/html;
        charset=3DISO-8859-1">
      Hello,<br>
      <br>
      I'd like to introduce two proposed BIPs. They are primarily
      focused on implementing the payment protocol using bluetooth
      connections. I've been working on automated point of sale devices
      and bluetooth communication is critical in my mind due to the
      potential lack of internet access at many points of sale, either
      due to lack of cellular internet coverage, lack of payee providing
      wireless internet, and/or due to financial constraints of the
      payer prohibiting them from maintaining a cellular internet
      service plan. These BIPs are largely modeled after the current
      functionality of Andreas Schildbach's android Bitcoin Wallet's
      bluetooth capability. I've discussed the communication scheme with
      him in depth and believe these proposals to clearly and accurately
      represent the communication scheme.<br>
      <br>
      There is also an additional &amp;h=3D parameter added to the
      bitcoin: URI scheme which applies to both bluetooth and http
      payment protocol requests which allows for a hash of the payment
      request to be included. This hash was proposed by Andreas as an
      amendment to BIP72, but others preferred not to amend BIP72 since
      it has already been put into place. The current version of
      Schildbach's bitcoin wallet already supports the "h parameter".<br>=

      <br>
      I'd appreciate feedback from everyone, particularly wallet
      developers as widespread bluetooth support among wallets is very
      important to me. I'm also very new to this mailing list as well as
      the BIP writing process, so I'd appreciate your understanding if
      my conventions are not standard. I am currently using the naming
      conventions "TBIP", so that I can propose <i>temporary</i> BIP
      numbers, and cross reference between the two. Obviously these will
      change if the BIPs are formally adopted. You can find a copy of
      these proposed BIPs at the following links:<br>
      <ul>
        <li><a moz-do-not-send=3D"true" class=3D"moz-txt-link-freetext"
href=3D"https://github.com/AndySchroder/bips/blob/master/tbip-0074.mediaw=
iki">https://github.com/AndySchroder/bips/blob/master/tbip-0074.mediawiki=
</a></li>
        <li><a moz-do-not-send=3D"true" class=3D"moz-txt-link-freetext"
href=3D"https://github.com/AndySchroder/bips/blob/master/tbip-0075.mediaw=
iki">https://github.com/AndySchroder/bips/blob/master/tbip-0075.mediawiki=
</a><br>
        </li>
      </ul>
      <br>
      If you are interested, you can see a demonstration of many of the
      proposed features using Schildbach's wallet and my fuel pump in a
      video I recently created: <a moz-do-not-send=3D"true"
        class=3D"moz-txt-link-freetext"
        href=3D"https://youtu.be/kkVAhA75k1Y">https://youtu.be/kkVAhA75k1=
Y</a>
      . The main thing not implemented is multiple URLs for the payment
      protocol, so, as a hack, I'm just presenting https vi QR code and
      bluetooth via NFC on my fuel pump for now.<br>
      <br>
      <br>
      <br>
      There are a few known issues that could be improved to this
      bluetooth communication scheme as well as the general payment
      protocol and myself and Andreas would like to receive feedback
      regarding concerns and potential solutions. Some of the known
      issues are:<br>
      <br>
      <ul>
        <li>There may seem to be some inconsistency in the connection
          header messages between the payment request connection and the
          payment connection. This is largely because it is how Andreas
          originally implemented the communication and is hesitant to
          change it since there are many instances of is software
          already deployed that implement this scheme.</li>
        <li>The current method uses an unauthenticated bluetooth
          connection for bluetooth 2.1 and newer devices (subject to man
          in the middle attacks, but not passive eavesdroppers), and an
          unsecure and unauthenticated connection for older devices. The
          known concerns here are that someone within 100 meters of the
          payer could track the bitcoin addresses used for the
          transaction and could possibly replace the refund address by
          submitting a forged payment message to the payee. Requiring
          bluetooth 2.1 and authenticating the connection out of band
          unfortunately don't seem to be as straightforward/simple of a
          task with most bluetooth libraries (although I'd love for
          someone to prove me wrong). It's possible this communication
          scheme could be extended to use an https "like" protocol that
          would not care if the underlying bluetooth connection is
          authenticated or encrypted. It's actually possible that http
          over a bluetooth socket (instead of tcp socket) could be
          implemented, however it is presently uncertain whether this
          would be too slow, too much overhead (both on the devices
          software and communication), or if http could easily be run
          over bluetooth sockets on all platforms.</li>
        <li>There is no acknowledgement failure message possible in the
          payment protocol, only an acknowledgement message or lack of
          acknowledgement message. This issue seems to be a concern and
          as a result, the memo field is used to send an "ack" or "nack"
          in Schildbach's wallet. Can we add a boolean status field to
          the payment acknowledgement message?<br>
        </li>
        <li>I'd personally like a new optional boolean field added to
          the "PaymentDetails" portion of the <span class=3D"nc">"Payment=
Request"


            to allow for the payer's wallet to match the "Output"
            optional "amount" fields as a total amount of all Outputs,
            rather than requiring the amount for each output to be
            matched exactly. As it currently is, the payee can specify
            multiple receiving addresses in order to require a payer
            split up the payments so that when the payee then goes to
            spend the funds later, they don't necessarily have to give
            their payees as much knowledge of their balances and
            spending and receiving habits and sources. As the payment
            protocol currently is requiring all output amounts to be
            matched exactly for each output, there is no flexibility
            given to the payer in order to reduce a merging or
            unnecessary diverging of account funds, which can reduce the
            privacy of both the payer and the payee. If the payee were
            given the option to allow the payer the option to divide the
            amounts amount the outputs intelligently, there can be some
            privacy gained.</span></li>
        <li><span class=3D"nc">Amount of data stored in QR codes may be
            getting large when a backwards compatible URL is used (for
            wallets that don't support the payment protocol) and can be
            difficult to scan with outdoor screens that have an extra
            weather resistant pane when in direct sunlight.</span></li>
        <li><span class=3D"nc">The number of offline transactions of a
            wallet is limited to the known unspent outputs when they go
            offline. </span>Long term, I'd like to see wallet devices
          that can use systems such as Kryptoradio's DVB-T based
          broadcast (but this will need yet another radio!). Another
          project may be to develop a blockchain query protocol of some
          kind where retailers can provide access to blockchain data so
          that customer's wallets can update their known unspent outputs
          via bluetooth. It's possible such a bluetooth system could be
          used in combination of "Kryptoradio" like broadcasts to
          provide multiple blockchain references.</li>
        <li>The additional payment_url approach is a bit sloppy of a
          solution in the PaymentDetails portion of the PaymentRequest.
          It would have been ideal to just change this from an optional
          field to a repeated field, however, the backwards
          compatibility in the protocol buffer format will provide the
          last item in the array for a repeated field (to a code that
          expects it to be an optional field), rather than the first.
          Because of this, backwards compatibility with https payment
          requests wouldn't work if the payment_url field is just
          changed to a repeated field.</li>
        <ul>
          <li>Possible alternatives to what is described in the proposed
            BIP</li>
          <ul>
            <li>Change payment_url to a repeated field and then reverse
              the order of the parameter numbers in the payment_url,
              compared to the bitcoin URL "r parameter".</li>
            <li>Create an additional, new payment_url_multi repeated
              field (or some better name), and then leave the original
              payment_url field in there for backwards compatibility
              (and then maybe phase it out in the future).<br>
            </li>
          </ul>
          <li>Reference<br>
          </li>
          <ul>
            <li><a moz-do-not-send=3D"true" class=3D"moz-txt-link-freetex=
t"
href=3D"https://developers.google.com/protocol-buffers/docs/proto#updatin=
g">https://developers.google.com/protocol-buffers/docs/proto#updating</a>=
</li>
            <ul>
              <li>"<code>optional</code> is compatible with <code>repeate=
d</code>.
                Given serialized data of a repeated field as input,
                clients that expect this field to be <code>optional</code=
>
                will take the last input value if it's a primitive type
                field or merge all input elements if it's a message type
                field."</li>
            </ul>
          </ul>
        </ul>
      </ul>
      <br>
      <br>
      Your comments and suggestions would be greatly appreciated.<br>
      <br>
      <pre class=3D"moz-signature" cols=3D"72">--=20
Andy Schroder</pre>
      <br>
    </blockquote>
    <br>
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