Information security has become one of the most significant issues in data communication. Steganography and cryptography are the well-known techniques for securing secret message. Steganography hides a message inside some other digital media and cryptography obscures the content of the message. Using these techniques separately, does not provide total security to our secret message. In order to protect the secrecy and privacy of the secret message, we need to integrate steganography and cryptography together to provide strong communication system that will be able to withstand intruders.
In this thesis, we proposed an image steganography method that focuses on bitmap color images of 24-bit. This method used Tagged Image File Format (TIFF) image as cover images because of its high embedding capacity. To achieve a higher level of security, we used AES 128-bit encryption algorithm to encrypt the secret message before embedding it inside an image using the Least Significant Bit (LSB) method. We improved LSB method by decreasing the amount of changes made to the cover image. In our experiment, a comparative analysis is made to demonstrate the effectiveness of the proposed method by computing Mean Square Error (MSE) and Peak Signal to Noise Ratio (PSNR). The results show that our approach maintains image quality and higher level of security.

資訊安全近期在資料通訊中佔有很大的重要議題。其中，影像藏密及密碼學都是確保祕密訊息的方法。影像藏密是把一張訊息藏在數位媒體並且遮掩一些資訊。但是如果分開使用這些技術，並沒有辦法完整的保護資訊安全。為了要保護資訊安全及機密資訊，我們必須結合影像藏密及密碼學去提供更強大的資訊通訊來防止入侵者。
在這篇論文中，我們提供一個影像藏密的方法去專注在24位元的彩色影像。這項方法使用了標籤圖像文件格式，並且在使用最低有效位（LSB）方法的圖像嵌入裡面，使用AES 128位元的加密算法的秘密信息進行加密，透過減少到封面圖像所做的更改量來提高LSB的方法。在這項實驗中，比較分析了通過計算均方誤差（MSE）和峰值信噪比（PSNR）證明了該方法的有效性。最後的結果顯示此方法能保持圖像質量和安全的更高的水平。

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