Cryptography Reference
In-Depth Information
Digital HDTV:
Still picture:
1920 pels1080 lines1.5 byte/pixel8 bit/byte = 24.883 Mbit/frame
Motion picture:
24.883 Mbit/frame30 frame/sec = 746.496 Mbit/frame
On account of the huge amount of multimedia data, compression is nec-
essary for practical applications. Ways of achieving necessary multimedia
compression will be described in Chapter 2. Detailed schemes with loss-
less compression, lossy compression, practical applications, and multimedia-
related standards are discussed in Part II of this topic.
1.2 Concepts and Requirements of Digital Watermarking
1.2.1 Fundamental Concepts of Digital Watermarking
Owning to the popularity of the Internet and the nature of the multimedia
information that permits lossless and unlimited reproductions, the need to
embed securely owner identity and other information into multimedia is ur-
gent [5, 6, 7, 8, 9, 10, 11, 12, 13, 14]. The protection and enforcement of
intellectual property rights for digital multimedia is now an important issue.
Modern digital watermarking technology has a short history since 1993 [5, 15].
A typical application of digital watermarking is to identify the ownership
of a multimedia object or content by embedding the owner mark. This is
known as the watermark . Typically, most multimedia applications require an
imperceptible and robust watermark. There are other demands that require
perceptible or fragile watermarking. Some relevant terminology and classifi-
cations are described in Fig. 1.1.
The high level diagram of a generic watermarking scheme is shown in
Fig. 1.2. Typically, a watermark insertion process is shown in Fig. 1.2(a). Here
we have the original media (X), which may be an image for example, and the
encoder inserts a watermark (W ) into it. The result is the marked media X
,
for example, a marked image. In this embedding, process, a key may be used
in order to produce a more secure watermark. This key is regarded as part of
the encoding process. The dashed line in Fig. 1.2 indicates that the key may
be needed for a particular design. The watermark may be extracted by use of
a decoder, illustrated in Fig. 1.2(b). It may alternatively be detected using a
detector. This is shown in Fig. 1.2(c). In the former process, in addition to the
test media (X
′′
), the original media with or without a key may be needed. In
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