4 ms·

No, not really: if you take a picture of something, it won't have the exact same pixel values every time you take it. A QR code would be way easier.

ars 9y ago
It's scaled to 32x32 black and white. The pixel values don't have to be that similar, only reasonable close.
- Cyberdog 9y ago
  But then I'm guessing it fudges pixels/bits until it ends up with a prime number. Is that fudging deterministic, or just random?
  - progval 9y ago
    It tests primality of numbers greater than the number corresponding to the input image by incrementing. So it's deterministic.
    - Cyberdog 9y ago
      Incrementing… So pixels at the bottom right of the image are the most likely to be flipped from the source image. Interesting. (Edit: Assuming big-endianness and left-to-right, top-to-bottom printing of the pixels/bits) Nonetheless, yes, using this to create security keys would probably be a good way to lose your bitcoin. :D
      - ars 9y ago
        Clearly the current implementation is not enough, but I wonder if there is a way to do this properly with actual security, and yet be reproducible for a normal human (we can assume the same camera and lighting). Maybe some kind of marker in the image that is used for cropping and scaling? Being able to see a particular image, and at a particular time of day (or indoors I guess), would definitely be an interesting security key. (Hollywood: feel free to take this idea and do it badly :)
    - esnard 9y ago
      Actually it's decrementing: https://github.com/geonnave/primg/blob/master/index.html#L82 https://github.com/geonnave/primg/blob/master/index.html#L82 I guess it could change the whole image if the last pixels are "000...000", which happens when the top-left corner has an opposite color to the bottom-right one. This image can't be "primed" correctly, for example: https://i.imgur.com/ms3sXtF.png https://i.imgur.com/ms3sXtF.png
- progval 9y ago
  But that's only 1024 bits, assuming values of each pixel is independant from its neighbors. Which it isn't, so you are well under 1024 bits.
  - nojustno81 9y ago
    Jesus Christ, no. It won’t work. Not every goddamn idea you people have is good. When will you learn that?

ars 9y ago

It's scaled to 32x32 black and white. The pixel values don't have to be that similar, only reasonable close.

Cyberdog 9y ago
But then I'm guessing it fudges pixels/bits until it ends up with a prime number. Is that fudging deterministic, or just random?
- progval 9y ago
  It tests primality of numbers greater than the number corresponding to the input image by incrementing. So it's deterministic.
  - Cyberdog 9y ago
    Incrementing… So pixels at the bottom right of the image are the most likely to be flipped from the source image. Interesting. (Edit: Assuming big-endianness and left-to-right, top-to-bottom printing of the pixels/bits) Nonetheless, yes, using this to create security keys would probably be a good way to lose your bitcoin. :D
    - ars 9y ago
      Clearly the current implementation is not enough, but I wonder if there is a way to do this properly with actual security, and yet be reproducible for a normal human (we can assume the same camera and lighting). Maybe some kind of marker in the image that is used for cropping and scaling? Being able to see a particular image, and at a particular time of day (or indoors I guess), would definitely be an interesting security key. (Hollywood: feel free to take this idea and do it badly :)
  - esnard 9y ago
    Actually it's decrementing: https://github.com/geonnave/primg/blob/master/index.html#L82 https://github.com/geonnave/primg/blob/master/index.html#L82 I guess it could change the whole image if the last pixels are "000...000", which happens when the top-left corner has an opposite color to the bottom-right one. This image can't be "primed" correctly, for example: https://i.imgur.com/ms3sXtF.png https://i.imgur.com/ms3sXtF.png
progval 9y ago
But that's only 1024 bits, assuming values of each pixel is independant from its neighbors. Which it isn't, so you are well under 1024 bits.
- nojustno81 9y ago
  Jesus Christ, no. It won’t work. Not every goddamn idea you people have is good. When will you learn that?