30-06-2012, 12:34 PM
Steganography In Images
Steganography In Images.pdf (Size: 87.22 KB / Downloads: 30)
ABSTRACT:
In this paper, we aim to present a general introduction to steganography or data-hiding as
it is sometimes just known. We then turn to data-hiding in images. When examining these
data-hiding techniques, we bear in mind Bender's specifications, such as degradation of
the cover data must be kept to a minimum, and the hidden data must be made as immune
as possible to possible attack from manipulation of the cover data.
INTRODUCTION:
Steganography, from the Greek, means covered, or secret writing, and is a long-practised
form of hiding information. Although related to cryptography, they are not the same.
Steganography's intent is to hide the existence of the message, while cryptography
scrambles a message so that it cannot be understood.
Steganography in Images
In this section we deal with data encoding in still digital images. In essence, image
steganography is about exploiting the limited powers of the human visual system (HVS).
Within reason, any plain text, cipher text, other images, or anything that can be embedded
in a bit stream can be hidden in an image. Image steganography has come quite far in
recent years with the development of fast, powerful graphical computers, and
steganographic software is now readily available over the Internet for everyday users.
IMAGES:
To a computer, an image is an array of numbers that represent light intensities at various
points, or pixels. These pixels make up the image's raster data. An image size of 640 by
480 pixels, utilizing 256 colors (8 bits per pixel) is fairly common. Such an image would
contain around 300 kilobits of data.
Digital images are typically stored in either 24-bit or 8-bit per pixel files. 24-bit images
are sometimes known as true colour images. Obviously, a 24-bit image provides more
space for hiding information; however, 24-bit images are generally large and not that
common. A 24-bit image 1024 pixels wide by 768 pixels high would have a size in
excess of 2 megabytes. As such, large files would attract attention were they to be
transmitted across a network or the Internet. Image compression is desirable. However,
compression brings with it other problems, that shall be explained shortly.
Image Compression:
Image compression offers a solution to large image files. Two kinds of image
compression are lossless and lossy compression. Both methods save storage space but
have differing effects on any uncompressed hidden data in the image.
Lossy compression, as typified by JPEG (Joint Photographic Experts Group) format files,
offers high compression, but may not maintain the original image's integrity. This can
impact negatively on any hidden data in the image. This is due to the lossy compression
algorithm, which may ``lose'' unnecessary image data, providing a close approximation to
high-quality digital images, but not an exact duplicate. Hence, the term``lossy''
compression. Lossy compression is frequently used on true-colour images, as it offers
high compression rates.
Conclusion:
In this paper, we take an introductory look at steganography. Several methods for hiding
data in, images were described, with appropriate introductions to the environments of
each medium, as well as the strengths and weaknesses of each method.The key algorithm
for designing the steganography system has been dealt. Most data-hiding systems take
advantage of human perceptual weaknesses, but have weaknesses of their own. We
conclude that for now, it seems that no system of data-hiding is totally immune to attack.
Steganography In Images.pdf (Size: 87.22 KB / Downloads: 30)
ABSTRACT:
In this paper, we aim to present a general introduction to steganography or data-hiding as
it is sometimes just known. We then turn to data-hiding in images. When examining these
data-hiding techniques, we bear in mind Bender's specifications, such as degradation of
the cover data must be kept to a minimum, and the hidden data must be made as immune
as possible to possible attack from manipulation of the cover data.
INTRODUCTION:
Steganography, from the Greek, means covered, or secret writing, and is a long-practised
form of hiding information. Although related to cryptography, they are not the same.
Steganography's intent is to hide the existence of the message, while cryptography
scrambles a message so that it cannot be understood.
Steganography in Images
In this section we deal with data encoding in still digital images. In essence, image
steganography is about exploiting the limited powers of the human visual system (HVS).
Within reason, any plain text, cipher text, other images, or anything that can be embedded
in a bit stream can be hidden in an image. Image steganography has come quite far in
recent years with the development of fast, powerful graphical computers, and
steganographic software is now readily available over the Internet for everyday users.
IMAGES:
To a computer, an image is an array of numbers that represent light intensities at various
points, or pixels. These pixels make up the image's raster data. An image size of 640 by
480 pixels, utilizing 256 colors (8 bits per pixel) is fairly common. Such an image would
contain around 300 kilobits of data.
Digital images are typically stored in either 24-bit or 8-bit per pixel files. 24-bit images
are sometimes known as true colour images. Obviously, a 24-bit image provides more
space for hiding information; however, 24-bit images are generally large and not that
common. A 24-bit image 1024 pixels wide by 768 pixels high would have a size in
excess of 2 megabytes. As such, large files would attract attention were they to be
transmitted across a network or the Internet. Image compression is desirable. However,
compression brings with it other problems, that shall be explained shortly.
Image Compression:
Image compression offers a solution to large image files. Two kinds of image
compression are lossless and lossy compression. Both methods save storage space but
have differing effects on any uncompressed hidden data in the image.
Lossy compression, as typified by JPEG (Joint Photographic Experts Group) format files,
offers high compression, but may not maintain the original image's integrity. This can
impact negatively on any hidden data in the image. This is due to the lossy compression
algorithm, which may ``lose'' unnecessary image data, providing a close approximation to
high-quality digital images, but not an exact duplicate. Hence, the term``lossy''
compression. Lossy compression is frequently used on true-colour images, as it offers
high compression rates.
Conclusion:
In this paper, we take an introductory look at steganography. Several methods for hiding
data in, images were described, with appropriate introductions to the environments of
each medium, as well as the strengths and weaknesses of each method.The key algorithm
for designing the steganography system has been dealt. Most data-hiding systems take
advantage of human perceptual weaknesses, but have weaknesses of their own. We
conclude that for now, it seems that no system of data-hiding is totally immune to attack.