Encoding

Steps for Encoding

1. Partition the image into 8x8 pixel blocks
2. For each of the 8x8 blocks X_r:
3. Discard the LSBs.
4. Combine with the entire image X to produce a bitstream of the pixels.
5. Hash the combined bitstream of pixels together using MD5 to produce P_r.
6. The watermark B_r is XORed with the hashed pattern P_r to produce W_r.
7. The result W_r is encrypted using private-key K‘ to produce ciphertext C_r.
8. Replace the LSBs of X_r with the ciphertext C_r.
9. Recombine all the blocks X_r to produce the watermarked image.

Citations

1. J. Pan et al., "Fragile watermarks" in Intelligent Watermarking Techniques, River Edge, N.J.: World Scientific, 2004, ch. 5, sec. 5.2.2, pp. 18-19.