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A One Time Pad (OTP) sounds perfectly secure if we are to believe Wikipedia. But on the surface it also sounds ridiculously impractical - how does one securely distribute the OTP?
Idea: why not have someone distribute it for you in plain sight of everyone?
Presuming I can keep the details secret (as I would with an encryption key), if I wanted to communicate securely, why wouldn't I harvest the images from some source of abundant images (Facebook, news site, dating site, porn site, etc), and make use of the noise in their lower bits to create a one-time-pad?
Even assuming someone hacks my PC and can narrow down the image(s) I may have used, an image is not in itself an OTP - you need to extract the OTP bits from the image pixels. That can be done in an enormous number of ways. The secrets to doing it are more or less equivalent to conventional encryption keys.
E.g. I could shuffle the pixels in the chosen image before using them in one of N! possible shuffles for N pixels, which is enormous after even 50 pixels. I could also extract the OTP bits from the image pixels starting from any pixel and in a bunch of scanning directions/modes. And which bits do I use, and in which order? Plenty more permutations there to be guessed at by anyone wanting to crack my code.
Which raises a different possibility: why don't I distribute the algorithm for permuting the pixels and extracting the bits to create the OTP from a single image?
I'm suggesting this because I noticed a while ago that the original image posted on Wikipedia of the Mona Lisa happened to have prime numbers for its width and height. That sounds like a useful property to someone wanting to generate an OTP. You don't suppose someone is already using it for that, or some other cryptographic purpose, do you? After all, this image size is the only one that Wikipedia has repeated, which seems... improbable as a coincidence.
Yet all of this completely contravenes the advice of "don't roll your own". Does that advice still apply to an OTP that is truly only ever used once, even if its random bits are pseudo-randomly selected each time in one of extraordinarily many ways from a single source of truly random bits?