Digital Book Watermarking via Glyph Code Transformation
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Solution Overview
Problem
Existing digital book watermarking methods are not robust against collusive attacks, as they can be easily reversed by identifying and replacing modified codes, allowing for the reconstruction of the original un-watermarked text.
Innovation Solution
A method that creates a new typeface by modifying the coding of glyphs using a bijective function linked to an identifier, making the watermarked book graphically identical to the original but with unique coding, ensuring that the encoded identifier cannot be removed or altered by comparing different copies, thus enhancing robustness against collusive attacks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a new text is developed by replacing codes in the pre-existing text with similar codes from the pre-existing typeface, then the water-marking is imperceptible to users and the new text displays graphically identical characters, but the water-marking becomes vulnerable to collusive attacks where modified codes can be identified and replaced to reconstruct the original un-water-marked text
Solution Approach 1:
The patent applies parameter changes by modifying the code-to-glyph mapping relationships in the typeface rather than changing the glyphs themselves. A bijective function transforms the original code set into a new code set, creating a unique code assignment for each water-marked copy. This parameter transformation ensures that while the visual display remains identical, the underlying code structure becomes identifier-specific and resistant to collusive attacks, as attackers cannot identify which codes are modified without knowing the bijective function used.
Solution Approach 2:
The patent implements preliminary action by pre-defining a bijective function that establishes the relationship between the original codes and the transformed codes before the water-marking process. This pre-established mathematical relationship allows the system to generate unique code mappings for each identifier while ensuring that the transformation is reversible only with knowledge of the specific bijective function. The preliminary setup creates a secure framework that prevents later reconstruction of the original text without the identifier.
2Loss of information
If the water-marking method uses code replacement in the pre-existing text, then the identifier can be encoded in the position of codes, but the method allows easy reconstruction of the original text by comparing multiple copies and replacing second codes with first codes
Solution Approach 1:
The patent fundamentally changes the parameter being encoded from code position to code-glyph mapping relationship. Instead of using the position of codes in the text to encode the identifier, the system transforms the mapping between codes and glyphs using a bijective function. This parameter change means that the same code may map to different glyphs in different water-marked copies, or the same glyph may be represented by different codes, making it impossible to identify modified codes through simple comparison without knowledge of the specific bijective function used for each copy.
Data Source
AI summary
The method for water-marking digital books with parameters includes developing, for each parameter, a new typeface on the basis of a pre-existing typeface, by creating at least one new code/glyph pair. The method includes developing a new coded text on the basis of the pre-existing coded text by replacing, in the pre-existing coded text, at least one code or group of codes from the pre-existing typeface. The method further includes allowing display of a character or a combination of characters from the digital book by the code or the group of codes from the new typeface allowing display of the graphically identical character or combination of characters on any screen. The code/group of codes from the new typeface has/have at least the code from the new code/glyph pair. The method also includes providing the new coded text and the new typeface as a water-marked digital book.