Digital invisible ink
Chun-Hsiang Huang, Yu-Feng Kuo, Ja‐Ling Wu · 2006
A novel steganographic approach analogy to the real-world secret communication mechanism, in which secret messages are written on white papers using invisible ink like lemon juice and are revealed only after the papers are heated, is proposed. Carefully-designed informed embedders now play the role of "invisible ink"; some pre-negotiated attacks provided by common content-processing tools correspond to the required "heating" process. Theoretic models and feasible implementations of the proposed digital-invisible-ink watermarking approach based on both blind-detection spread-spectrum watermarking and quantization watermarking schemes are provided. The proposed schemes can prevent the supervisor from interpreting secret messages even when the watermark extractor and decryption tool, as well as session keys, are available to the supervisor. Furthermore, secret communication systems employing the proposed scheme can aggressively mislead the channel supervisor with fake watermarks and transmit genuine secrets at the same time.