Security Element Covert Encoding Using Dual Wavelet Decomposition
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Solution Overview
Problem
Existing methods for encoding information in security documents using digital watermarks can be easily detected through wavelet decomposition, making them vulnerable to counterfeiting.
Innovation Solution
The method involves using two different wavelets for wavelet decomposition transformations, making it impossible to extract the encoded information without knowing both wavelets, ensuring the encoded information is not recognizable to human observers and is protected against unauthorized reading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If digital watermarking using wavelet decomposition is used to encode information in security documents, then information can be covertly embedded in the image, but the encoded information can be easily detected through wavelet decomposition analysis
Solution Approach 1:
The patent applies parameter changes by using multiple different wavelets (changing the wavelet parameter) in sequence during the decomposition process. Instead of using a single wavelet, the method employs a series of different wavelets, making it computationally infeasible for attackers to detect the encoded information through standard wavelet decomposition analysis, while still allowing authorized verification using the known wavelet sequence.
2Productivity
If standard wavelet decomposition is used for information encoding, then the encoding process is simple and efficient, but the security against counterfeiting is weak
Solution Approach 1:
The patent maintains encoding efficiency while improving security by changing the wavelet parameter across multiple decomposition stages. This approach preserves the relative simplicity of the wavelet transformation method but adds a layer of security through parameter variation, making the system both productive and reliable against counterfeiting attempts.
Solution Approach 2:
The patent segments the wavelet decomposition process into multiple stages, each using a different wavelet. This segmentation of the encoding process into discrete steps with varying parameters both maintains computational efficiency and significantly strengthens security against counterfeiting by requiring knowledge of the entire wavelet sequence for successful decoding.
3Difficulty of detecting and measuring
If information is encoded in a way that is imperceptible to human observers, then security against visual inspection is improved, but verification and extraction of the information becomes more difficult
Solution Approach 1:
The patent resolves this contradiction by using parameter changes (different wavelets) that create an encoding imperceptible to human observers yet verifiable through automated processes. The visual imperceptibility is maintained while the verification complexity is managed through the use of a predetermined wavelet sequence known to authorized systems, enabling efficient machine-based verification without simple visual detection.
Data Source
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Figure 2a~2c
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AI summary
The invention relates to a method for producing a security element with secretly coded information in a graphical image (1'), to a security element of this kind and to a method for verifying a security element of this kind. The method for producing a security element comprises the following steps: provision of a graphical 2-dimensional image (1); provision of the information (31) to be coded; performance of wavelet decomposition transformations, in order to decompose the image progressively into sub-images (2-15, 21-25, 41-44) corresponding to frequency bands; wherein the sub-images are derived from the transformation coefficients; alteration of individual transformation coefficients for a selected one of the sub-images (25), in order to insert the information to be coded into the selected sub-image (25); performance of wavelet reverse transformations, in order to obtain a coded image (1') that corresponds to the provided graphical image (1) and that stores the 1st information (31) in concealed form, characterised in that the progressive performance of the wavelet decomposition transformations that are performed in order to produce the sub-image (2-15, 21-25, 41-44) into which the information (31) is inserted involves not only wavelet decomposition transformations with a 1st wavelet (a) but also at least one wavelet decomposition transformation with a 2nd wavelet (b), which is different from the 1st wavelet, being performed.