I had another idea for steganography in Jpegs specifically. So in Jpeg there is something called the Quantization Table that's responsible for weighting all the

I had another idea for steganography in Jpegs specifically. So in Jpeg there is something called the Quantization Table that's responsible for weighting all the AC values in each 8x8 block. When you encode, you divide the DCT values by the corresponding DQT value so a large quantization value has a greater chance of reducing the DCT to 0, allowing us to truncate the high frequencies (we want this). To decode we just multiply by the corresponding quantization value and run the inverse DCT. But nothing prevents us from putting 0s in the Quantization table. And any pixel put in those values wouldn't contributed to the rasterized image. So we can cut off some of the high frequency bins entirely and then store whatever in them.