الفهرس 
1. IntroductionOnly 14 pages are availabe for public view
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Abstract
the rapid growth in the demand and consumption of the digital multimedia
content in the past decade has led to some valid concerns over issues such as
content security, authenticity, and digital rights management. Multimedia data hiding
is defined as imperceptible embedding of information into a multimedia host. It
provides potential solutions such as one used in satellite and medical applications and
military which is called reversible data hiding. Reversibility allows original media to
be completely recovered from marked media without distortion after embedded
message has been extracted.
Toward this direction, this thesis presents two proposed reversible data
hiding methods.
In the first proposed method, a reversible data embedding method that hides
data through images in the spatial domain is proposed. Though the proposed
reversible data embedding method distorts the original image to embed data into the
image, the method restores the original image as well as extracts hidden data from the
image in which the data are embedded. To guarantee the losslessness of data
embedding, all pixel values after embedding must be in the dynamic range of pixels.
Because the proposed method modifies some pixels to embed data and leaves other
pixels as their original values in the spatial domain, it can easily keep all pixel values
after embedding in the dynamic range of pixels. Thus, both the capacity and the image
quality of generated images are simultaneously improved. Moreover, the proposed
reversible data embedding method uses three embedding parameters based on the
statistics of pixel blocks to embed and extract data. By using these embedding
parameters, this method does not require any reference images to extract embedded
data nor any memorization of the positions of pixels in which data are hidden to
extract embedded data. In addition, the proposed reversible data embedding method
can control the capacity for hidden data and the quality of images conveying hidden
data by controlling the three parameters. Simulation results show the effectiveness of
the proposed reversible data embedding method; in particular, it offers images with
superior image quality compared with conventional methods.
Based on experimental results, the proposed reversible data embedding
method has more than 25% embedding capacity improvement ratio. Experimental
results show that the proposed reversible data embedding method not only can
improve the payload capacity but also can maintain good image quality.
In the second proposed method, a reversible data hiding scheme based on
histogram modification is proposed. The distribution of pixel differences is used to
achieve large hiding capacity while keeping distortion low. The proposed improved
histogram-based reversible data hiding approach employed a 3-by-3 box filter
prediction scheme and has the capability of embedding two bits for each pixel. The
main objective of the proposed improved histogram-based technique is to increase the
heights of the peak points around the origin in the histogram, in order to increase the
embedding capacity of the proposed improved histogram-based reversible data hiding
method. The proposed improved histogram-based reversible data hiding scheme
provides high payload capacity for gray level images and maintains high stego-image
quality after hiding data. So, the proposed improved histogram-based reversible data
hiding method improves the capacity for hidden data and maintains good quality for
stego images, simultaneously. Finally, this method restores the original image as well
as extracts hidden data from stego image.