Covert Communication by Information Hiding Techniques via Autostereograms
|關鍵字:||立體圖;資訊隱藏;秘密通訊;Autostereograms;information hiding;covert comunication|
序列立體圖」。第一種秘密傳輸方法 利用替換LSB 技術建立灰階隨機點立體
體圖 提出2x2 區塊編碼資訊隱藏方法將秘密訊息藏在立體圖中。最後一種秘
In this study, three kinds of autostereogram images together with different data hiding techniques are proposed for the purpose of covert communication grayscale random dot autostereogram with the LSB replacement technique, black and white wallpaper autostereogram with the distortion-reducing block coding technique, and black-and-white random dot image sequence autostereogram with random-pattern block coding technique. The proposed covert communication method via grayscale random dot autostereograms requires two masks, one being a cover mask and the other a secret mask or text. After a grayscale random dot cover autostereogram is created with the cover mask, the message is then converted into a bit string, which along with a key is then embedded into the cover autostereogram by LSB replacement, yielding a stego-autostereogram. With the same key, the hiding process can be reversed to recover the secret autostereogram composed with the secret mask. Wallpaper autostereogram generation is almost the same as autostereogram generation but the proposed covert communication method via them adopts a different information hiding technique. In additional to the mask images and the key required, a black and white pattern is necessary for the creation of the autostereogram and the hiding task is implemented while creating the autostereogram. The encryption of a secret message uses a specific 22 block pattern that represents different bit strings of the message. Such encryption is done in the vertical stripe pattern before completing the background, so it can be hidden in the blind spot of the autostereogram. The pattern with the encrypted data is then used to create the stego-autostereogram. Subsequently, the process can be reverted to get the hidden secret autostereogram produced with the secret message embedded. The last proposed method of covert communication is implemented on a sequence of black-and-white random dot autostereograms. The generation of each autostereogram image in the sequence is similar to that of a single autostereogram except that instead of using single cover and secret masks, sequences of multiple frames are processed. However, the employed technique is random-pattern block coding, which uses sixteen patterns to match sixteen different bit strings of the message. Moreover, all the data hiding techniques implement special features of the generation processes of the respective types of autostereograms to conduct data encryption. Different types of backgrounds are developed in these techniques due to the necessity of not attracting much attention from hackers and not exposing the secret message hidden. The hiding techniques are just simply complementing the types of backgrounds produced. Good experimental results are also presented, which show the feasibility and practicality of the proposed methods for covert communication via autostereograms.