Negative Digital Watermarking for Signal Authentication
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Solution Overview
Problem
Existing signal authentication methods in radio communication systems are inadequate as they can be detected and counterfeited by attackers, lacking sufficient security and complexity, and often cause significant signal impairment.
Innovation Solution
A method that projects a digital signal onto a vector space orthogonal to a digital watermark vector, allowing for authentication by checking orthogonality, which is verified through a simple scalar product, enabling multiple watermarks to be embedded without interference and with minimal signal distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a digital watermark is added to a signal in a positive manner (concealed pattern), then authentication capability is provided, but the watermark can be detected and counterfeited by attackers
Solution Approach 1:
The patent inverts the traditional watermarking approach by using negative watermarking instead of positive watermarking. Instead of adding a detectable pattern to the signal, the method removes or suppresses specific frequency components that would correspond to a watermark pattern. This inversion makes the watermark undetectable through conventional means while maintaining authentication capability, as the absence of certain frequency components serves as the authentication mechanism.
Solution Approach 2:
The patent converts the potential harm of signal modification into a benefit by using the removal of frequency components as the authentication mechanism. The 'harm' of altering the signal is transformed into a useful authentication feature where the specific pattern of removed components serves as the watermark, making it both undetectable and secure against counterfeiting.
2Reliability
If conventional watermarking methods are used, then authentication is achieved, but significant signal impairment occurs
Solution Approach 1:
The patent changes the parameter of watermark embedding from additive (positive) to subtractive (negative). By modifying the watermark embedding approach to remove frequency components rather than add them, the method achieves authentication with minimal signal impairment. The subtractive approach allows for more precise control over the amount of signal modification, preserving signal quality while maintaining authentication capability.
3Reliability
If multiple watermarks are embedded in a signal, then authentication robustness is improved, but interference between watermarks increases
Solution Approach 1:
The patent segments the watermark embedding process by assigning different frequency components to different watermarks. Each watermark is embedded in a distinct frequency region through the negative watermarking process, which prevents interference between multiple watermarks. This segmentation approach allows multiple watermarks to coexist in the same signal without mutual interference, improving authentication robustness.
Solution Approach 2:
The patent moves the watermark embedding from the time domain to the frequency domain, utilizing different frequency dimensions for multiple watermarks. By operating in the frequency domain and assigning specific frequency components to different watermarks, the method enables multiple watermarks to be embedded without interference, as each occupies a distinct frequency dimension.
Data Source
Figure 1~3
AI summary
The invention concerns a transmission of a digital signal, in which - when it is transmitted, a vector corresponding to a digital signal to be transmitted, having the form of a sequence of N symbols, is projected onto a vector space, said vector space being orthogonal to at least one non-zero vector corresponding to a sequence of symbols defining a digital watermark, and - when it is received, the digital signal is authenticated by checking the orthogonality of a vector, corresponding to said received digital signal and having the form of a sequence of symbols, relative to said at least one vector defining a digital watermark.