الفهرس 
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Abstract
Chaos complex behaviour, based on iterating simple equations, is the occurrence of randomness
and unpredictability in completely deterministic manner. Its most important sensitivity to initial
conditions can be used to generate an infinite number of chaotic random sequences that can find
application in the newly evolving fields of security and identity protection of digital data, digital
images, and digital videos through Cryptography, Steganography and Digital Watermarking.
As the chaotic random sequence is used for embedding the watermark, embedding non-
linearity combined with chaos extreme initial conditions sensitivity ensure that a watermark
generated even by a key in the vicinity of the correct one will not be positively detected in a
watermarked image or extracting hidden data.
This thesis presents several techniques to secure multimedia that depend on using spread
spectrum broadband techniques based on tailored matched chaotic maps. Three new image
authentication and information hiding schemes based on chaotic encryption are proposed. All
schemes are based on the invariant property of the chaotic sequence matching histogram as well
as chaotic map synthesis using a confidential starting point. In the first method we present a
chaos-based spread spectrum watermarking algorithm for still images. The chaotic map together
with the initial condition, used to produce the pseudo-random signal, behave as embedding and
detecting key. In the second method the chaotic sequence having the same histogram of the
chosen location and a cover image are used to generate the chaotic scrambled cover sequence.
The DWT of this sequence is then used to modulate a part, having a confidential location, of the
discrete wavelet transform of a host image. Either the sequence or the cover image can be the
hidden information. In the third method, only the chaotic sequence histogram features are hidden
in the host image 2DWT coefficients. This chaotic sequence is considered as a public key for all
system users. Each user can use this public key and his confidential initial condition to generate
his own chaotic sequence. Each user can use his own chaotic sequence to authenticate his data
and to implement secure communication [6]. The difference between using a chaotic map that
matches the host image in generating the embedding sequence and using an unmatched one is
also discussed.
The thesis also investigates the possibility of generating a random chaotic sequence, having a
uniform histogram, using a chaotic sequence matching a given histogram and a chaotic sequence
matching the complement of this histogram. To study the relation between these two sequences
three methods are used to determine the complement of the histogram . In the third method, to
obtain a sequence having uniform histogram, it is found necessary to combine, through simple
concatenation, two relatively computed different lengths of first and second chaotic sequences
generated using original and complement histograms of the second or first methods.
This section presents briefly the contents and organization of the remaining chapters of the
thesis Chapter 2 provides an introduction to chaos theory, its properties, history of random
generators and its relation to chaos. Chapter 3 briefly discusses watermarking, its requirements,
types and communication model. Chapter 4 introduces the map tailoring method. Chapter 5
introduces the random sequence generation technique we developed. Chapter 6 presents the
proposed methods for watermarking and their results. Chapter 7 offers a technique to use the last
proposed method in chapter 6 for multi=user watermarking. Last Chapter 8 includes our
conclusions and future work.