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Date: Fri, 6 Feb 2015 14:54:49 +0100
Message-ID: <CANEZrP23tfTzCfk2eXUOPX=CFCg6GKn4HO5Rb3ZxeOJQtEQCHw@mail.gmail.com>
From: Mike Hearn <mike@plan99.net>
To: Eric Voskuil <eric@voskuil.org>
Content-Type: multipart/alternative; boundary=047d7bb7092ca25c5e050e6bc354
Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>,
	Andreas Schildbach <andreas@schildbach.de>
Subject: Re: [Bitcoin-development] Two Proposed BIPs - Bluetooth
 Communication and bitcoin: URI Scheme Improvements
Precedence: list

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BLE meets a different use case than regular Bluetooth. BLE is designed to
allow always-on broadcast "beacons" which are conceptually similar to NFC
tags, with very low power requirements. The tradeoff for this ultra-low
power consumption and always on nature is the same as with NFC tags: you
get very little space for data, and they are essentially one way. That's
why a common use case for it is to trigger some other mechanism like a
classical Bluetooth socket or HTTPS connection.

I think BLE has a role to play in Bitcoin payments, but probably not for
actually transferring payment data. Rather, a merchant should be able to
drop a BLE beacon in their shop, and then wallet apps can use that to learn
where to download a payment request/upload a payment message. But the
actual data transfer would still take place over Bluetooth, Wifi or the
internet.

That leads to the question of what the beacon broadcasts. A bitcoin URI is
the obvious answer: the problem is a URI contains an address. No problem
for the "throw money at a live performer" use case but a problem for the
cafe use case. If we are willing to mandate BIP70 and remove the static
address part from the URI the we get a "uri that points to a url" which is
a bit inefficient but at least lets us distinguish bitcoin beacons from
other kinds. That still leaves the fundamental question raised by the
Airbitz spec - how does your wallet download the right payment request?

Unfortunately that's a tough UI problem. I don't think comparing long hex
strings manually is a good way to go. This seems less user friendly than a
QR code.

Once we solve that problem, how BLE beacons can trigger payments will all
fall into place. The tech part isn't the hard part.

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<div dir=3D"ltr"><div class=3D"gmail_extra">BLE meets a different use case =
than regular Bluetooth. BLE is designed to allow always-on broadcast &quot;=
beacons&quot; which are conceptually similar to NFC tags, with very low pow=
er requirements. The tradeoff for this ultra-low power consumption and alwa=
ys on nature is the same as with NFC tags: you get very little space for da=
ta, and they are essentially one way. That&#39;s why a common use case for =
it is to trigger some other mechanism like a classical Bluetooth socket or =
HTTPS connection.</div><div class=3D"gmail_extra"><br></div><div class=3D"g=
mail_extra">I think BLE has a role to play in Bitcoin payments, but probabl=
y not for actually transferring payment data. Rather, a merchant should be =
able to drop a BLE beacon in their shop, and then wallet apps can use that =
to learn where to download a payment request/upload a payment message. But =
the actual data transfer would still take place over Bluetooth, Wifi or the=
 internet.</div><div class=3D"gmail_extra"><br></div><div class=3D"gmail_ex=
tra">That leads to the question of what the beacon broadcasts. A bitcoin UR=
I is the obvious answer: the problem is a URI contains an address. No probl=
em for the &quot;throw money at a live performer&quot; use case but a probl=
em for the cafe use case. If we are willing to mandate BIP70 and remove the=
 static address part from the URI the we get a &quot;uri that points to a u=
rl&quot; which is a bit inefficient but at least lets us distinguish bitcoi=
n beacons from other kinds. That still leaves the fundamental question rais=
ed by the Airbitz spec - how does your wallet download the right payment re=
quest?</div><div class=3D"gmail_extra"><br></div><div class=3D"gmail_extra"=
>Unfortunately that&#39;s a tough UI problem. I don&#39;t think comparing l=
ong hex strings manually is a good way to go. This seems less user friendly=
 than a QR code.</div><div class=3D"gmail_extra"><br></div><div class=3D"gm=
ail_extra">Once we solve that problem, how BLE beacons can trigger payments=
 will all fall into place. The tech part isn&#39;t the hard part.</div></di=
v>

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