Text Watermarking via Inter-Word Spacing Adjustment
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Solution Overview
Problem
Current methods for protecting sensitive information in documents, such as encryption and firewalls, are inadequate as they do not prevent authorized individuals from copying or transmitting documents, and existing text watermarking techniques introduce noticeable noise or require image conversion, which complicates the process of tracking document ownership.
Innovation Solution
A method for embedding hidden data in text documents by applying error correction coding and spreading it over a carrier signal, adjusting word and line spacing to encode messages, which can be detected without the original document, even after printing and scanning, using a combination of spreading functions and BCH error correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If image watermarking techniques are applied to text documents, then document protection and tracking are improved, but noticeable white noise is introduced and document readability deteriorates
Solution Approach 1:
The patent extracts the watermark embedding process from the image domain and applies it directly to the text domain by modifying inter-word spaces. This separates the watermarking function from the visual rendering, allowing text documents to be watermarked without converting them to images, thereby avoiding the introduction of white noise while maintaining readability.
Solution Approach 2:
The patent replaces the visual/mechanical image processing approach with a textual/mathematical approach. Instead of modifying pixel values in an image, the system embeds watermarks by adjusting the spacing between words in the text document, using mathematical operations on the text structure rather than visual processing.
2Adaptability or versatility
If text documents are rasterized into images for watermarking, then image watermarking techniques can be applied, but processing complexity and time increase
Solution Approach 1:
Instead of converting text to image and then applying image watermarking (the conventional approach), the patent inverts the process by directly applying watermarking techniques to the text structure itself. This reverses the traditional workflow and eliminates the unnecessary rasterization step, reducing processing complexity while maintaining versatility.
Solution Approach 2:
The patent extracts the essential watermarking functionality from the image processing pipeline and applies it directly to text documents. By removing the rasterization step and applying watermarking operations directly to the text structure (modifying inter-word spaces), the system achieves the same protection goals with significantly reduced processing complexity.
3Object-affected harmful factors
If encryption and access restriction techniques are used, then unauthorized viewing is prevented, but document copying and transmission by authorized individuals cannot be stopped
Solution Approach 1:
The patent introduces an intermediary mechanism - the digital watermark - that operates independently of encryption and access control systems. This intermediary provides an additional layer of security that tracks document ownership and usage, enabling the system to detect and trace unauthorized copying and transmission even when encryption is bypassed or access restrictions are circumvented.
Solution Approach 2:
The patent makes the document protection system multi-functional by combining encryption, access control, and watermarking in a single integrated solution. The watermarking component provides universal tracking capability that works across different scenarios (electronic viewing, printing, copying, transmission) and complements existing security measures rather than replacing them, thereby enhancing overall document security reliability.
Data Source
AI summary
A text watermarking method embeds an auxiliary message in an original electronic text document to form a watermarked text document. The method applies a spreading function to message symbols to spread the symbols over a carrier, which forms a modulated carrier. It maps elements of the modulated carrier to corresponding inter-word spaces in the electronic text document, and applies an embedding function to modify the corresponding inter-word spaces according to elements of the modulated carrier signal such that the modified inter-word spaces hide the modulated carrier signal in the watermarked text document. The message symbols are automatically decodable from the watermarked document without the original electronic text document. A compatible decoder extracts the auxiliary message from a printed or electronic watermarked text document. The decoder automatically measures inter-word spaces in the watermarked text document. It estimates elements of a modulated carrier signal embedded in the inter-word spaces to form an estimated modulated carrier signal, and applies a de-spreading function to the estimated modulated carrier signal to extract message symbols.