Digital watermarking technique and its security applications – digital watermark
The use of digital methods of embedding hidden in images, sounds, documents, books, videos and other digital products, in order to achieve the purpose of existence of hidden messages.
HC screen Special Indian network Digital Watermarking (Digital watermarking) technology in recent years the rise of international information security community as a cutting-edge research topics, is in close proximity to the practical application of information hiding. Digital watermarking (Digitalwatermarking) technology in recent years the rise of international information security community as a cutting-edge research topics, is a very close to the practical application of information hiding. With information security, information hiding, data encryption Dengjun close.
Digital watermarking algorithm through some tags will have a specific meaning (watermark), using digital methods of embedding hidden in images, sounds, documents, books, videos and other digital products, in order to achieve the purpose of existence of hidden message, using interests of the owner to prove ownership of their works, and as identification, prosecution of illegal infringement of evidence, while on the watermark detection and analysis of reliability to ensure the integrity of digital information, making intellectual property protection and digital multimedia security and effective means of The protection of intellectual property, confidential Communicate And content identification fields have a wide range of application.
A digital watermark of the main components
Digital watermark in theory, based on the rapid development in recent years, wavelet analysis (WaveletAnalysis). Digital watermarking technology has strong robustness to be perceived, hidden place of safety, no ambiguity, and the computing efficiency and so on. Watermark embedding and extraction system is divided into two parts, each part of it by the corresponding software and hardware. This composition forms
effectively improve the level of anti-counterfeiting technology, which greatly increases the difficulty of counterfeiters counterfeiting. The following features:
(1) as an identifier of digital watermark is not visible in the form of visual hide Print Products, in natural light or artificial light irradiation, the naked eye can not distinguish between whether to add a digital watermark printed markings and does not affect the need to protect the print (watermark bunker), the original image of the visual senses, only by a specific computer or computerized machine reading device can determine.
(2) print the watermark in the hidden tag is not only a random location can be arbitrary, so the print has played a role in multiple security.
(3) print the watermark in the hidden tag does not change after printing location, handling personnel and the time change, in the above link does not leak and the possibility of proliferation.
(4) to embed watermark printed tag does not change the appearance of the original print properties, not the current printing equipment have special requirements, without changing the printed material, but not to increase the printing costs.
The basis of modern security technology, trends, printed mark in the digital watermark detection method using DSP chips and random access memory with machine-readable identifier. This high-performance machine-readable identification devices are easy to mass production, and good product consistency; low cost; operation simple to use, reliable; determine the authenticity of the software product to run fast, safe and good, quick updates and so on.
Second, the core of digital watermarking technology
1, wavelet-based Generation and hidden digital watermarking algorithm: wavelet algorithm, the digital image of the spatial domain data by discrete wavelet transform (DWT) into the corresponding wavelet coefficients, and according to the type of information to be hidden, appropriate coding and its deformation, and then hide the amount of information according to the size and the corresponding security objectives, choose the square of the frequency domain coefficient sequence.
Finally, the digital image of the frequency domain coefficients by the inverse transform into the spatial domain data.
2, anti-copying watermark technology: When the counterfeiters get with digital watermark printing and packaging, it will surely try to copy (such as high-precision digital scanner), to prevent digital watermark information is copied, the hidden digital watermark embedded software watermark information using chromatography equivalent for a given algorithm, this method can guarantee counterfeit in the process of adjustment to meet the original image's color, you can not avoid change chromatography equivalent, so fundamental to ensure the watermark will not be copied.
3, anti-fading technology: from digital images to print, to go through plate making, printing processes such as multi-channel, digital watermark on the characteristics of each process must be attenuated, in order to ensure the final print digital watermarking have enough signal strength, digital watermark embedding watermark information in the generated software fully considered sufficient signal strength to ensure that through a number of processes when the signal strength (robustness) can still be a reliable machine-readable.
4, machine-readable digital watermark test: the test machine-readable digital watermarking technology can eliminate the uncertainty of human factors to improve test speed and enhance hidden information (watermark) to identify the security, can and RFID , UV, magnetic stripe and other security inspection equipment has been composed of mature multi-dimensional security system, to enhance integrated Security Level.
To develop a low-cost, mass production can be industrialized as Detector-like machine-readable digital watermark inspection equipment, machine reading devices should be used embedded operating system (Vix / Vox), with DSP chip as the core processor using the camera and face formation CMOS (CCD) image sensor devices to form a portable and mobile, AC and DC, can be networked, the software can quickly update the digital security detection equipment.
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