[Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE) transfer of Payment URI

Thu Feb 5 13:46:44 UTC 2015

Thanks Paul, for writing up your protocol!

First thoughts:

For a BIP standard, I think we should skip "bitcoin:" URIs entirely and
publish BIP70 payment requests instead. URIs mainly stick around because
of QR codes limited capacity. BIP70 would partly address the "copycat"
problem by signing payment requests.

In your Motivation section, I miss some words about NFC. NFC already
addresses all of the usability issues mentioned and is supported by
mobile wallets since 2011. That doesn't mean your method doesn't make
sense in some situations, but I think it should be explained why to
prefer broadcasting payment requests over picking them up via near field
radio.

On 02/05/2015 09:01 AM, Paul Puey wrote:
> Airbitz has developed and implemented a method for communicating a
> bitcoin URI across Bluetooth (BLE) or any other P2P, mid range,
> wireless, broadcast medium. The currently documented implementation is
> available in our iOS and Android mobile wallet (updated Android version
> with BLE coming in about 1 week). We would like to have the BIP pulled
> into Github for review and discussion. Here is the current BIP:
> 
> 
> BIP: TBD
> 
> Title: P2P Wireless URI transfer
> 
> Authors: Thomas Baker <tom’at’airbitz.co <http://airbitz.co>>, Paul Puey
> <paul’at’airbitz.co <http://airbitz.co>>
> 
> Contributors: Joey Krug <joeykrug’at’gmail.com <http://gmail.com>>
> 
> Status: proposal
> 
> Type: Standards Track
> 
> Created: 2015-01-12
> 
> 
>     Table of Contents
> 
>   *
> 
>     Abstract
> 
>   *
> 
>     Motivation
> 
>   *
> 
>     Specification
> 
>   *
> 
>     Compatibility
> 
>   *
> 
>     Examples
> 
>   *
> 
>     References
> 
> 
>     Abstract
> 
> This is a protocol for peer-to-peer wireless transfer of a URI request
> using an open broadcast or advertisement channel such as Bluetooth,
> Bluetooth Low Energy, or WiFi Direct.
> 
> 
>     Motivation
> 
> There are disadvantages for a merchant (requester) and customer (sender)
> to exchange a URI request using QR codes that can be eliminated by using
> wireless broadcast or advertisements.
> 
> Current QR code scan method to transfer a request URI from merchant
> (Requester) to customer (Sender) is cumbersome. A usual scenario is a
> merchant with a POS terminal for order entry and a separate tablet for
> transacting payments with bitcoin, and a customer with a smartphone.
> After the order is entered, the merchant enters payment request
> information into the tablet, generates the QR code representing the URI,
> and presents this to the customer. The customer prepares to scan the QR
> code with their smartphone by maneuvering the camera to the tablet. The
> tablet screen must be relatively clean, point at the customer, and held
> steady. The smartphone camera lens must be clean, point at the tablet
> screen, come into range, and held steady to focus and wait for a QR
> scan. Environmental conditions such as bright outdoor sunlight, indoor
> spot lights, or significant distance between QR code and camera can
> create difficult and cumbersome experiences for users.
> 
> Using a wireless local broadcast allows the merchant to just enter the
> payment and wait. The tablet and smartphone are not maneuvered to align
> in any way. The customer observes broadcast listings, selects the
> appropriate one from possible simultaneous broadcasts from other POS
> stations nearby, examines the URI request details such as amount, and
> decides whether to send funds, initiating a bitcoin network transfer.
> The merchant and customer then receive the transaction confirmations and
> are done with the sale. Merchant and customer devices are kept private
> and secured in their own possession.
> 
> The URI and other broadcast identification (Joe’s Grill #1) only contain
> public information. However, a copycat broadcaster acting as MITM might
> duplicate the broadcast simultaneously as the merchant, attempting to
> lure the customer to send funds to the copycat. That attack is mitigated
> with this broadcast method because of the partial address in the broadcast.
> 
> 
>     Specification
> 
> Requester generates a bitcoin URI request of variable length, and a
> limited descriptive identifier string. Requester then broadcasts the
> URI’s partial public address (<paddress>) plus identifier (<id>) over a
> publicly visible wireless channel.
> 
> Sender scans for broadcasts on their device, examines and selects the
> desired request by the identifier and partial address. This connects a
> data channel to Requester.
> 
> Requester sends full URI back over the data channel.
> 
> Sender device ensures <paddress> is part of the full URI public address
> and checks the full address integrity. Checking the broadcast and full
> URI integrity prevents a copycat device within range from copying the
> partial address and fooling the customer into sending funds to the
> copycat instead.
> 
> Below is a description of the protocol through Bluetooth Smart (Low Energy).
> 
> Requestor      Sender     - Bitcoin transaction roles
> 
> Peripheral     Central    - Bluetooth GAP definitions
> 
>   Mode           Mode
> 
> 1   |------------->|       - Requestor Advertises partial bitcoin: URI +
> Name
> 
>    |     ...      |       
> 
> 2   |<-------------|       - Subscribe then send sender's Name,
> requesting a response
> 
> 3   |------------->|       - ACK
> 
> 4   |<-------------|       - request Read Characteristic from peripheral
> 
> 5   |------------->|       - Sender receives full bitcoin: URI
> 
> 
>  1.
> 
>     Peripheral advertises over a service UUID a BLE extended
>     advertisement with a Scan Response containing the partial address of
>     a bitcoin URI and a Name, any plain text. The entire response is
>     limited to 26 characters. The first 10 make up the first 10
>     characters of the bitcoin URI public address where to send bitcoin,
>     and must be present. The remaining characters are any plain text
>     such as “The Habit 1” or “Starbucks-Reg 1”, more human readable
>     information. The partial address serves as a check against a nearby
>     attacker who may try to lure a Sender into sending payment to a
>     separate wallet by advertising a similar Scan Response but cannot
>     replicate a public address with the same leading 10 characters and
>     different trailing characters.
> 
>  2.
> 
>     When the Central scans the advertisement, it may display the Scan
>     Response in a human readable listing using the two pieces of
>     information. If Central chooses this advertisement to receive the
>     full request, it then subscribes to the service and writes the
>     characteristic (a second UUID) with it’s own name, or a blank if not
>     sending a name, to the Peripheral.
> 
>  3.
> 
>     Peripheral gets a characteristic write request of the Central’s
>     name, and acknowledges the receipt by sending a server response.
> 
>  4.
> 
>     Central receives a characteristic write (from the response) and
>     immediately requests the entire bitcoin URI by issuing a read
>     request on that characteristic.
> 
>  5.
> 
>     Peripheral receives the read request and sends the entire bitcoin
>     URI over that characteristic up to 512 bytes.
> 
> This ends the proposed specification as the bitcoin URI transfer is
> complete. The Sender would then normally confirm the request and decide
> whether to initiate the fund transfer.
> 
> 
>     Compatibility
> 
> There are no prior BIPs covering this.
> 
> 
>     Examples
> 
> Airbitz iOS Bluetooth Low Energy to Bluetooth Low Energy request transfer.
> 
> 
>     References
> 
> 
> 
> 
> 
> logo   
> 	*Paul Puey* CEO / Co-Founder, Airbitz Inc
> +1-619-850-8624 | http://airbitz.co <http://airbitz.co/> | San Diego
> <http://facebook.com/airbitz> <http://twitter.com/airbitz> <https://plus.google.com/118173667510609425617> <https://go.airbitz.co/comments/feed/> <http://linkedin.com/in/paulpuey> <https://angel.co/paul-puey>
> 
> *DOWNLOAD THE AIRBITZ WALLET:*
>  
> <https://play.google.com/store/apps/details?id=com.airbitz><https://itunes.apple.com/us/app/airbitz/id843536046>
> 
> 
> 
> 
> 
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