[Cryptography] Of writing down passwords

[Jerry Leichter]

On Sep 25, 2014, at 5:48 PM, Christian Huitema <huitema at huitema.net> wrote:
> ...John's question was about "reading reflections on eyes or glasses." We are not quite there yet. With a 1080p camera at 1 meter from your eyes, the eyes are typically 30 pixels wide, and the iris 10 pixels. This is not enough to read something. Even with the 41 Mpixels camera of the Nokia Lumia 1020, you will get less than 150 pixels for the eyes and less than 50 for the iris. Getting there, but not quite.
There's little reason for pixel density to get much higher.  Oh, there are certainly specialty uses, but the 41Mpixels on a Lumia have little practical use - they are there for bragging rights.

On the other hand, pixel density is only the relevant factor if you assume a particular image size and all magnification done after digitization.  If your iris is 10 pixels across, a 20x magnifying lens - nothing particularly exotic on an DSLR - makes it 200 pixels across.  The tiny lenses and imaging matrices in phones produce astounding results, but they are subject to fundamental physical limits (particularly diffraction limits) that stuff in more pixels can't solve.

If the question is "when will you be able to read text of the image of a human eye as taken by something reasonably related to today's cellphone camera", I think the answer is likely to be "never".  Even if it were physically possible, there's simply no reason for cell phone cameras to evolve in that direction.

On the other hand, if the question is "when could you create a photographic setup that would take a picture of a human eye from which you could extract text", the answer is that it could be done easily today.

                                                        -- Jerry