Improved DM-QIM watermarking scheme for PDF document

Minoru Kuribayashi, Kok Sheik Wong

Research output: Chapter in Book/Report/Conference proceedingConference PaperResearch

3 Citations (Scopus)


In any application of watermarking, the selection of feature vectors from a given multimedia content is important from the perspective of robustness and security. In the case of PDF document, the spaces between words and characters are commonly utilized for embedding watermark in the conventional schemes. Instead of modifying the space values directly, researchers proposed to manipulate the frequency components of the space values by using the quantization index modulation (QIM) watermarking method. The QIM method is further combined with dither modulation (DM) to enhance secrecy of watermark. In this paper, we improve the imperceptibility of watermarked PDF document by investigating into the DM operation. The proposed method selects the best secret key among some candidates which minimizes the degradation caused by embedding watermark. Information about the selected key is also embedded as side information so that the embedded watermark can be extracted without referring to the original PDF document. The degree of distortion caused by watermark embedding is quantitatively measured in our experiment. It is verified that the gain in terms of signal-to-noise ratio in the proposed method is increased with the number of secret key candidates.

Original languageEnglish
Title of host publication18th International Workshop, IWDW 2019 Chengdu, China, November 2–4, 2019 Revised Selected Papers
EditorsHongxia Wang, Xianfeng Zhao, Yunqing Shi, Hyoung Joong Kim, Alessandro Piva
Place of PublicationCham Switzerland
Number of pages13
ISBN (Electronic)9783030435752
ISBN (Print)9783030435745
Publication statusPublished - 2020
EventInternational Workshop on Digital Forensics and Watermarking 2019 - Chengdu, China
Duration: 2 Nov 20194 Nov 2019
Conference number: 18TH (Proceedings)

Publication series

NameLecture Notes in Computer Science
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


ConferenceInternational Workshop on Digital Forensics and Watermarking 2019
Abbreviated titleIWDW 2019
Internet address


  • Dither modulation
  • PDF document
  • Quantization index modulation
  • Watermark

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