Re: Is it possible to transfer data by using light
Re: Is it possible to transfer data by using light
- Subject: Re: Is it possible to transfer data by using light
- From: Sixten Otto <email@hidden>
- Date: Mon, 21 Sep 2015 08:54:39 -0700
On Sun, Sep 20, 2015 at 9:55 PM, Jens Alfke <email@hidden> wrote:
> But honestly, if you're going this route, it will be much faster to
> transmit QR codes, since each code contains thousands of bits.
>
Especially given that recent versions of iOS can detect and decode QR codes
automatically, much like face detection.
https://developer.apple.com/library/ios/documentation/AVFoundation/Reference/AVMetadataMachineReadableCodeObject_Class/index.html
https://developer.apple.com/library/ios/documentation/QuartzCore/Reference/CIQRCodeFeature/
> On Sep 20, 2015, at 7:21 PM, ico <email@hidden> wrote:
> >
> > After reading all of the replies, no one mentioned how to use iPhone to
> > detect the light changes (bright and dark) in codes, I just have no clue
> > how to make it works as long as I remember developers have no right to
> > access the light sensor, so I guess we have to use camera to achieve
> this,
> > but I just don't know how. Can anyone point me to something to read so I
> > can start digging into this and make the whole thing start to work?
> >
> > Thank you all.
> >
> > On Fri, 18 Sep 2015 at 20:38 Michael David Crawford <
> email@hidden>
> > wrote:
> >
> >> Do iOS devices support Trusted Computing in hardware? If so is it
> >> accessible to userspace apps?
> >>
> >> If so, you could store your phones secret in a write-only register.
> >> For the profoundly paranoid, even the duplication of your storage
> >> would not yield your phone's secret, The Bad Guy would need your
> >> personal phone.
> >>
> >> Modern Macs - to the best of my knowledge - provide trusted computing
> >> chips, on can access them from userspace with a modest bit of code.
> >> Michael David Crawford P.E., Consulting Process Architect
> >> email@hidden
> >> http://mike.soggywizard.com/
> >>
> >> One Must Not Trifle With Wizards For It Makes Us Soggy And Hard To
> >> Light.
> >>
> >>
> >>> On Fri, Sep 18, 2015 at 3:12 AM, Maxthon Chan <email@hidden>
> wrote:
> >>> The "over-the-shoulder" issue can be avoided using what is effectively
> a
> >> Diffie-Hellman on top of QR codes. This can be done using front-facing
> >> cameras on two devices placed face-to-face.
> >>>
> >>> Sent from my iPhone
> >>>
> >>>> On Sep 18, 2015, at 00:46, Pascal J. Bourguignon <
> email@hidden>
> >> wrote:
> >>>>
> >>>>
> >>>>
> >>>>> On 17/09/15 17:32, Michael David Crawford wrote:
> >>>>> And what the man said: I myself experience seizures in which I lose
> >>>>> consciousness for as long as three weeks. Before they were diagnosed
> >>>>> I would experience seizures while driving my car then suddenly find
> >>>>> myself in unfamiliar places without any clue how I got there.
> >>>>>
> >>>>> I don't know for sure but strongly suspect that modern computer user
> >>>>> interfaces caused my seizure disorder as well as that of my cousin.
> >>>>> Seizures are not otherwise found among any of our blood relatives.
> >>>>
> >>>> But then if you don't use the whole screen, but only the area that
> >>>> should be in front of the camera of the superposed phone, then users
> >>>> shouldn't be subjected to much stroboscopic light.
> >>>>
> >>>> Having the objective so close from the light source does not allow
> >>>> the camera to distinguish pixels; for example, a black to white
> >>>> transition takes about 1/10 of the height of the camera view.
> >>>> But this means that you might still able to transmit about ten pixels
> >> at once,
> >>>> and you can multiply that by a number of color that you can detect
> >> reliably
> >>>> being that out of focus. Basically, I would expect 8 colors to be
> >> clearly
> >>>> distinguishable. Actually, probably more colors should be
> >> distinguishable,
> >>>> if you can filter out the interferences due to the grid of the camera
> >> vs.
> >>>> the grid of the screen. So assume 4 bits for the color, and 9 areas,
> >>>> that's 36 bit/moment, and you should be able to do 30 moment/second,
> >>>> for a total of 1080 bit/second. A little less for ECC, about 1 KB/s
> >>>> is not too bad. It's good enough to transmit a good private key, and
> >> then
> >>>> transfer the data thru wifi.
> >>>>
> >>>>
> >>>> Of course, if you move the camera out to focus on the screen, then
> >>>> you can transmit at a higher speed things like QR codes, but they
> >>>> could also be seen over the shoulder by high resolution cameras.
> >>>>
> >>>> --
> >>>> __Pascal J. Bourguignon__
> >>>> http://www.informatimago.com/
> >>>>
> >>>> _______________________________________________
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