On 17/09/15 07:06, Jens Alfke wrote:
On Sep 16, 2015, at 9:06 PM, Jonathan Hull <jh...@gbis.com> wrote:
The big question would be why you want to do it. It is most likely easier to
transfer via wifi (also traveling at the speed of light, and optimized for data
transfer) or bluetooth.
Secure pairing, as you said, is one use. You need to ensure that the two
devices involved are exactly the ones you think they are, and WiFi or Bluetooth
don’t work because they see everything in range.
But it’s much higher bandwidth to use something like a QR code, where you can
send several thousand bits simultaneously. It’s pretty easy to send and receive
QR codes using APIs already available in iOS and Mac OS. You can send an entire
cryptographic key, and use that to bootstrap secure communication over
traditional networking.
To read QR codes you need a camera.
In the case of Toymail, they just need one photovoltaic cell to input a
serial signal.
Any I/O peripheral can be used to communicate between devices.
eg. you could also use speaker/microphone to emit a sound, possibly even
an ultrasound; but sound would have the same problem as bluetooth, being
omnidirectional.
On the other hand, QRcodes, or full screen flashes, are visible at least
as far as sound or bluetooth can be detected, and are also not very
directional.
There's also NFC, but IIRC, there's no public API to use it on iOS.
If the two phones are superposed, then only the small rectangle of the
screen that's in front of the camera needs to transmit the message (the
rest of the screen could transmit random data to confuse neighbors).
--
__Pascal J. Bourguignon__
http://www.informatimago.com/
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