theoretic model for steganography

Throughout history, people have sought secret means of protecting their property and their knowledge from being stolen. Watermarking and copyright marking, for instance, attempt to keep property secure from thieves. Cryptography and steganography aim to keep knowledge safe from spies.
In the spatial domain, we first present an efficient multi-level embedding procedure for 3D polygonal meshes. Our algorithm, which is the first technique to take advantage of the full vertex features of these meshes, achieves high capacity relying on three independent degrees of freedom. We deal with distortion through a new modified multi-level embedding procedure. Embedding that relies on the angle between triangle planes is not appropriate to a long and narrow triangle, because such embedding can cause larger distortion for a larger radius. To solve this, we embed messages based on the arc length, which efficiently avoids apparent distortion while it achieves high capacity. Based on this approach, we also propose a virtual multi-level embedding procedure to support point-sampled geometries. It produces a unique virtual triangle for each point and embeds messages by modifying the point based on virtual geometrical properties. Then, we propose an adaptive minimum-distortion estimation procedure to achieve higher capacity in each vertex by changing the vertex’s position with minimum distortion distance.
As we demonstrate in this dissertation, the proposed approaches, based on both the spatial and representation domains, can be combined to achieve higher capacity. In other words, we successfully combine both domains for steganography. Experimental results show significant improvements in terms of capacity, visual appearance, and performance with respect to the most recent, advanced techniques. These improvements will make this kind of application more widely available.Finally, all of our approaches are blind schemes, requiring no 3D cover model for message extraction, and they are secure, since retrieving the message without the key is virtually impossible. These algorithms are simple yet efficient and are robust against affine transformations. Our techniques are a feasible alternative to steganographic approaches for 3D models
. Our technique is adaptive, simple, efficient, and secure, and has proven to be feasible in steganography.In short, this dissertation presents the main issues related to the context of steganography for 3D models. We discuss steganography for HDR images, and we explore the main applications making use of secret messages and their need of reliable, high-capacity techniques. Among these techniques, we restrict our work to blind steganographic schemes with high capacity, adaptability, and no distortion. These techniques are simple, efficient, and generalizable. Moreover, they are secure in the cryptographic sense. Because research in this field is growing and diversifying, a great deal of additional work is needed. Development in the area of steganography will continue. The novel and original ideas for steganographic applications we offer in this dissertation can benefit many applications in cryptography and copyright marking, as well. We hope that our work will inspire more research in these areas.

theoretic model for steganography

密碼學（cryptography）與偽裝學（steganography）則致力於監視者環伺的脅迫下仍能安全且有效的保障重要訊息。其中，密碼學著重於掩飾訊息的內容，令其無法被人理解、解讀；偽裝學則為一門通訊的藝術亦為一門通訊的科技技術。
現在發展更厲害的三維模型偽裝技術。必須在讓人無法發現影像的變形，而有效率地嵌入大量的資訊隱匿於三維模型之中。如果能同時應用於三維多邊形模型及三維點模型，更能拓展其實用性。
針對日趨重要的高動態範圍影像提出相對應的偽裝技術。高動態範圍影像引起的興趣及注意，促使高動態範圍影像讓越來越的人去研究。即使傳統的低動態範圍影像也激起大量研究學者投入。高動態範圍影像的亮度範圍不但不固定且有著極大的變動範圍。因為此二種影像亮度範圍存在極大的差異性，發展高動態範圍影像的偽裝技術勢必面臨這樣的挑戰。

基於實際成像模型之動態模糊合成
一般電腦圖學或是虛擬實境中的影像呈現，多採用簡單的幾何成像模型進行影像的合成。本研究提出一種基於真實相機的成像模型，並考慮感測元件之非線性強度響應的影像合成技術。對於由物體與相機快速相對移動所產生的動態模糊，本研究所提出的方法可應用於空間不變或可變性的情況，並合成出較一般所採用的線性模型更為真實的影像。

　 　　

立體顯影之高動態範圍影像合成
以兩架攝影機同時拍攝的方式，擷取並合成具立體顯影之高動態範圍影像。我們利用兩張影像的特徵點對應來推算相機反應函數，透過對應點搜尋演算法進行兩張影像之套合，並以合成之高動態範圍影像對進行景物深度的重建，達成具立體顯影且易於合成新視角影像之目的。

首先針對三維模型之偽裝學進行深入地研究，並進一步地探討高動態範圍影像之偽裝學，也探討秘密訊息的主要應用及可靠性與高訊息嵌入量的必要性。

密碼傳奇 心得

密碼傳奇　這本書分為兩個部份，第一個是有關於歷史戰爭時的密碼
另外一個部份是其他加解密的方法
對於歷史的部份，我並沒有多看的很仔細
因為我對於歷史這方面，有很大的困擾XD

但是對於他加解密的部份覺得還滿有趣的
其中他書中所提及的＂凱薩密表＂
他舉了很多的例子，利用不同的條件算出解答
再利用凱薩密表，去找到真正要表達的訊息
但如果沒有算出解答的話
也可以試２５次的凱薩密表得到真正的答案
我反而覺得他書裡面提及的例子比較有趣
例如：跳舞小人
用了福爾摩斯的一個劇情去解釋那破解密文的方式
但是要先假設哪個是e，這個字，才能慢慢去推敲整篇大意
我覺得這個例子還滿好玩的
利用偵探小說的內容去解釋這樣加解密的方法
比一直看歷史介紹加解密還更讓人能看的懂

調色盤比較

←未隱藏

←要被隱藏的圖

←隱藏後

可以看出明顯第二張有白色雜訊的點點

檔案大小相差越大，顯現出來的效果會越明顯

An information-theoretic model for steganography

An information-theoretic model for steganography with a passive adversary is proposed. The adversary’s task of distinguishing between an innocent cover message C and a modified message S containing hidden information is interpreted as a hypothesis testing problem. The security of a steganographic system is quantified in terms of the relative entropy (or discrimination) between the distributions of C and S, which yields bounds on the detection capability of any adversary. It is shown that secure steganographic schemes exist in this model provided the covertext distribution satisfies certain conditions. A universal stegosystem is presented in this model that needs no knowledge of the covertext distribution, except that it is generated from independently repeated experiments.
-------------------------------------------------------------------------------------------------
一種隱秘對手訊息的理論被提出。對手的任務區分合法覆蓋消息C和修改信息包含在隱藏信息之間，被解釋為一種假設檢驗的問題。在安全的隱寫系統的量化計算的區別的分佈在C和S之間，這樣產生的邊界檢測能力上的任何對手。結果表明，存在安全隱寫計劃，在這個模型所提供的覆蓋文件滿足某些條件。一個普遍的隱秘系統提出，在這個模型需要知識的覆蓋文件分佈，除了它是產生獨立的反覆試驗。

S-Tool 研究心得

放入要隱藏的圖片，然後輸入密碼

















就隱藏好了











接著另存新檔
不過檔名要打＂.BMP＂
不然之後存好後會打不開









之後要打開的話...
就也是丟在S TOOL裡









輸入密碼就可以跑出來被隱藏的圖

這個操作還滿簡單的，我記得之前老師的課有說過這個工具

現在實做過，覺得還滿好玩的

雖然感覺很精簡，但是隱藏功能都有

因為先看過其它同學的心得了

所以遇到的問題就比較少！＠＠