5 ms·

I think a better solution is to adjust the color slightly. You can easily get 3 or 4 bits of encoded data for every pixel in the image. Just take the least sign

by gizmo 17y ago

I think a better solution is to adjust the color slightly. You can easily get 3 or 4 bits of encoded data for every pixel in the image. Just take the least significant bit of the red, green and blue colors. You go from 16.7 million to 2 million colors, but that shouldn't be a problem. The human eye cannot see the difference anyway. Only in perfect gradients that kind of difference can maybe be noticed, so then the solution is to pick grainy pictures. Photos (especially of poorly lit environments) should be perfect. They're very grainy by nature, so it will be especially difficult to trace where the data resides. Because you can hide so much data in the image, you can get very creative with where and how you do the encoding.

stcredzero 17y ago
How about a filter that takes ordinary images, but turns them into low-light photos? Or just turns them into grainy photos? The grain can then be shifted around for purposes of the encoding.
- GavinB 17y ago
  I was actually thinking about this last night as a means of hiding text or pictures. I would just round each pixel's R, G, and B values off to either even or odd. Even stands for 0, odd for 1. That gives you three bits per pixel and hopefully would be very hard to detect visually with, for example, a nature photograph. Then you just encode another image in 8-tone grayscale at the same size. That's what I was after, I haven't done the calculation for how large an image you'd need to encode real files.
fauigerzigerk 17y ago
So it will be difficult to detect visually, but isn't this rather trivial to find algorithmically? Not that I know much about cryptoanalysis, but it seems to me that this is a very weak form of steganography.
- khafra 17y ago
  It's reasonably hard to detect if just the least significant bit is random, but if you do the last three significant bits you don't even need an algorithm--you can see the jagged, broken histogram.
torressr3 17y ago
Yeah but you still would need the original picture to compare with.
sp332 17y ago
Spore actually does this with the PNG files from the "Sporepedia". You can actually import an image of the creature you want from the Sporepedia webpage and the playable 3D creature will appear in the game! http://news.ycombinator.com/item?id=703719 http://news.ycombinator.com/item?id=703719

by gizmo 17y ago

stcredzero 17y ago

How about a filter that takes ordinary images, but turns them into low-light photos? Or just turns them into grainy photos? The grain can then be shifted around for purposes of the encoding.

GavinB 17y ago
I was actually thinking about this last night as a means of hiding text or pictures. I would just round each pixel's R, G, and B values off to either even or odd. Even stands for 0, odd for 1. That gives you three bits per pixel and hopefully would be very hard to detect visually with, for example, a nature photograph. Then you just encode another image in 8-tone grayscale at the same size. That's what I was after, I haven't done the calculation for how large an image you'd need to encode real files.

fauigerzigerk 17y ago

So it will be difficult to detect visually, but isn't this rather trivial to find algorithmically? Not that I know much about cryptoanalysis, but it seems to me that this is a very weak form of steganography.

khafra 17y ago
It's reasonably hard to detect if just the least significant bit is random, but if you do the last three significant bits you don't even need an algorithm--you can see the jagged, broken histogram.

torressr3 17y ago

Yeah but you still would need the original picture to compare with.

sp332 17y ago

Spore actually does this with the PNG files from the "Sporepedia". You can actually import an image of the creature you want from the Sporepedia webpage and the playable 3D creature will appear in the game! http://news.ycombinator.com/item?id=703719 http://news.ycombinator.com/item?id=703719