Using a steganographic algorithm like least significant bit, can one hide a text in an image and then hide that image in another image?
For bitmap images, if you use all the pixels of the image (bad idea, it's very detectable) you need a first image 8/3 times bigger than the size of the text you want to hide (you can compress it).
- 8 because you need 8 pixels to hide one byte (one bit per pixel).
- 1/3 with color images, because you can hide a bit per channel/pixel.
After this, you can hide this image into another image 8 times bigger (again, 1 byte into 8 pixels).
For JPEG images the approach is different, because you are hiding information into the DCT coefficients. But it's the same idea.