The basic idea of digital watermarking
technology is to embed specific information (such as copyright information,
serial number, company logo, meaningful text, etc.) into various digital media
in China Printing, such as
image, voice, video, etc., in order to achieve the purpose of information
hiding. This process does not affect the normal use of the original data, does
not change the size of the original data, does not change the appearance of the
original information.
1. The anti-counterfeiting characteristics
of digital watermarking
The invisibility of digital watermarking
determines that it can be combined with other anti-counterfeiting technologies.
The printing anti-counterfeiting technology of digital watermark is different
from the traditional printing anti-counterfeiting technology. It completely
updates the traditional concept of printing anti-counterfeiting, and has unique
properties in the anti-counterfeiting of printed matter.
� Technology exclusivity. The embedding and
content of digital watermarking are random. The digital watermark hidden in
each printed matter can be different, and the position of watermark is also
random, which makes it difficult for forgers to counterfeit.
� Anti-counterfeiting investment is small
and the cost is low. Digital watermarking users can embed the
anti-counterfeiting information directly into the printed matter through the
special software processing of digital watermarking. There is no need to change
the production or printing process, add special materials, increase china printing
quality and printing costs and change the original design appearance.
� Technology upgrading is fast. According
to the characteristics of the products, different and easy to update the
special software, so that the corresponding printing anti-counterfeiting
technology can also be constantly updated.
� High confidentiality. In addition to the
individuation and unidirectionality, as well as the concealment hidden in the
media, digital watermarking technology can also be combined with private key
and public key control detection, which is more secure than other technologies.
� Product value added. Using the
internationally recognized high-end anti-counterfeiting technology digital
watermarking technology will make counterfeiters have nothing to do, so as to
enhance customers' trust in digital watermarking users and their products,
enhance and maintain the brand image of users, and improve the value-added
value of products.
2. The core technology of digital
watermarking
� Digital watermarking generation and
hiding algorithm based on wavelet algorithm.
In this paper, wavelet algorithm is used to
transform the spatial domain data of digital image into corresponding wavelet
domain coefficients through discrete wavelet transform (DWT). According to the
type of information to be hidden, it is encoded and deformed appropriately.
Then, according to the size of hidden information and the corresponding
security target, the square frequency domain coefficient sequence is selected.
Finally, the frequency domain coefficients of digital image are transformed
into spatial domain data by inverse transformation.
� Watermark anti duplication technology.
When the counterfeiter gets the printing
package containing the digital watermark, he will try to copy it (such as using
a high-precision digital scanner). In order to prevent the digital watermark
information from being copied, the digital watermark embedding software adopts
the algorithm of the given chromatographic equivalent when hiding the watermark
information. This method can ensure that the counterfeiter cannot avoid
changing the chromatogram when meeting the technical requirements of adjusting
the color of the original image in this way, the watermark will not be copied.
� Anti attenuation technology in China Printing.
From digital image to printed matter, it
has to go through many processes, such as plate making and printing. The
characteristics of digital watermark must be attenuated in each process. In
order to ensure that the digital watermark has sufficient signal strength on
the final printed matter, the digital watermark embedding software takes into
account the sufficient signal strength when generating the watermark
information to ensure that the signal strength (robustness) can still be
reliable after multiple processes Machine readable.
� Digital watermark testing
machine-readable.
Digital watermark inspection
machine-readable can eliminate the uncertainty of human factors, improve the
inspection speed, enhance the security of hidden information (watermark)
recognition, and can form a multi-dimensional anti-counterfeiting system with
RFID, UV, magnetic stripe and other mature anti-counterfeiting inspection
equipment to improve the comprehensive security level.
3� Framework of
digital watermarking
A typical digital watermarking model
consists of two main processes: one is the watermark embedding process, the
other is the watermark extraction or detection process. Each owner has a unique
watermark, or an owner can embed different watermarks into different objects.
Embedding watermark information into the carrier after preprocessing is called
embedding. Watermark embedding can be understood as transmitting a wideband
signal (watermark) on a wideband channel (original image) by spread spectrum
communication technology. The design of embedding stage mainly solves two
problems: the generation of digital watermark and the embedding algorithm.
Extracting watermark information from watermarked data or detecting the
existence of watermark information is called watermark extraction and
detection. At present, most watermarking schemes use the key when adding and
extracting. Only those who master the key can read the watermark.
The principle of digital watermarking
technology used for bill anti-counterfeiting is roughly the same as that of
audio and video, except that screening should be considered in the embedding
process of watermark, and the graphic information of printed matter should be
scanned in the process of watermark extraction and detection. In this process,
there is an analog-to-digital (A / D) conversion process. This requires that
the algorithm based on halftone digital watermarking technology must consider
these factors in the corresponding embedding and detection process. The process
of embedding and extracting is shown in Fig. 1 and Fig. 2.
4� Application of
digital watermarking in ticket security at China Printing and abroad printing
With the development of digital
watermarking technology, the application field of digital watermarking has been
expanded, from the early use of audio, video and other anti-counterfeiting to
the anti-counterfeiting of various certificates, bills and other high-value
commodities such as famous cigarettes, wine, precious drugs and so on. At present,
digital watermarking has been widely used in the anti-counterfeiting printing
of various tickets.
In Germany, digital watermarking is used to
prevent forgery of electronic photos, and the imperceptible information is
processed on the photos. This method can quickly and accurately determine the
authenticity of the documents. The Media Laboratory of Massachusetts Institute
of Technology (MIT) has studied how to add a unique and invisible digital
watermark to each image output by color printer and copier. By judging whether
the watermark exists or not from the scanned bill in real time, the
authenticity can be quickly identified. Japan adds watermarks to insurance
bills and proposes data hiding as a solution to identify the integrity of
digital photos, judge whether the photos have been tampered with and locate the
tampered places.
Digital watermarking technology is a hot topic
at home and abroad. It is in a stage of rapid and continuous development, and
its application field is also expanding rapidly. It plays a more and more
important role in the field of anti-counterfeiting printing and has become the
highlight of anti-counterfeiting packaging. Commercial paper has an important
value in social life, and the anti-counterfeiting work of commercial paper is
particularly necessary. The trend of counterfeit tickets has been banned for
many times. Ticket companies have adopted seven anti-counterfeiting measures on
a ticket, but they still cannot stop the spread of fake tickets. Therefore, it
is the development direction to choose the advanced digital watermarking
technology to replace the traditional anti-counterfeiting technology. With the
constant innovation of digital watermarking anti-counterfeiting technology, it
is bound to provide greater security for bill packaging anti-counterfeiting,
and will bring considerable economic and social benefits.
