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Please use this identifier to cite or link to this item: http://hdl.handle.net/2031/5675

Title: Design and study of image hiding scheme
Other Titles: Tu xiang yin cang ji hua de she ji ji yan jiu
圖像隱藏計劃的設計及研究
Authors: Sek, Ying Kit (石英傑)
Department: Department of Electronic Engineering
Degree: Master of Philosophy
Issue Date: 2009
Publisher: City University of Hong Kong
Subjects: Data transmission systems -- Security measures.
Data encryption (Computer science)
Cryptography.
Image processing -- Digital techniques.
Notes: CityU Call Number: TK5102.94 .S44 2009
vi, 74 leaves : ill. 30 cm.
Thesis (M.Phil.)--City University of Hong Kong, 2009.
Includes bibliographical references (leaves 69-71)
Type: thesis
Abstract: “Steganography”, a word defined as “the art of secret writing” by the Oxford English Dictionary. This is a way to hide secret message in other innocent looking cover media such as an essay or image. In ancient time, people write essay or draw a picture technically to camouflage hidden messages. Nowadays, we hide messages in digital images, video and audio in order to conceal the existence of any important messages transmitting through the Internet. “Cryptography”, which is widely used today in digital security, is a way to transform important messages into meaningless bit stream which is unreadable for human unless you have the right key to decrypt the message. Both “Cryptography” and “Steganography” are designed to protect important messages. However, cryptography transforms secret messages to meaningless bit stream and this raises suspicious from hackers and they may try to crack the encrypted messages. Steganography, on the other hand, aims at hiding messages in innocent looking cover media. The resulting bit stream is still readable as an image, video or any meaningful object. This characteristic makes steganography with the ability to avoid from being suspected. This research studied the current development in steganography with digital images as the cover media and it is also known as image hiding technique. Several existing image hiding techniques are investigated and analyzed. In this research, a novel lossy image hiding scheme is proposed with a better performance than the existing techniques. In the proposed scheme, we embed secret images into cover image by using block matching technique. By taking advantage of the similarity of two image blocks, we could achieve a higher embedding capacity. The scheme is simple and easy to implement. And yet, it produces good quality stego image and secret image. The above proposed scheme produce high quality image such that unintended observer will not be aware of the existence of the secret image. However, the embedding capacity is only one-to-one. i.e. embed one 512x512 secret image into another 512x512 cover image. In this research, a further analysis on the Quantized Error Matrix (QEM), the key elements in the above proposed scheme, is done to further improve the scheme. By further compressing and optimizing on the QEM, the scheme could embed eight secret images in one cover image. This is 800% increase in the embedding capacity. The result shows that the proposed scheme still produces high quality stego-image and acceptable quality of secret-image.
Online Catalog Link: http://lib.cityu.edu.hk/record=b2374817
Appears in Collections:EE - Master of Philosophy

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