Image steganography that could survive jpeg compression
I am trying to implement a steganographic algorithm where hidden message could survive jpeg compression.
The typical scenario is the following:
- Hide data in image
- Compress image using jpeg
- The hidden data is not destroyed by jpeg compressiona nd could be restored
I was trying to use different described algorithms but with no success. For example I was trying to use simple repetition code but the jpeg compression destroyed hidden data. Also I was trying to implementt algorithms described by the following articles: http://nas.takming.edu.tw/chkao/lncs2001.pdf http://www.securiteinfo.com/ebooks/palm/irvine-stega-jpg.pdf
Do you know about any algorithm that actually can survive jpeg compression?
Answer
You can hide the data in the frequency domain, JPEG saves information using DCT (Discrete Cosine Transform) for every 8x8 pixel block, the information that is invariant under compression is the highest frequency values, and they are arranged in a matrix, the lossy compression is done when the lowest coefficients of the matrix are rounded to 0 after the quantization of the block, these zeroes are arranged in the low-right part of the matrix and that is why the compression works and the information is lost.