Reversible Data Hiding for Encrypted Audios by High Order Smoothness

此篇論文呈現了實作在加密音訊上的可逆資訊隱藏技術，且此技術奠基於一個新的情境架構。在該情境中，資訊隱藏者在無法取得原始內容的情況下，將額外資訊嵌入已加密媒體中。接收者收到該檔案後若有事先溝通好的解密金鑰，可解密得到一份與原始內容非常相近的媒體。若其還有事先溝通好的資訊隱藏金鑰，則可再抽取出嵌在其中的額外資訊並將該媒體還原至最原始的狀態。 現存的媒體有很多種，最近幾年有人提出了針對加密圖片的資訊隱藏技術。但由於人耳對於聲音訊號較人眼對於影像訊號更為敏感，此篇論文採用更高次的平滑判斷方法，且讓原始檔案擁有者在加密前計算出之後還原媒體時會利用到的一些（旁）資訊。這兩個機制讓初步解密出來的媒體具有非常小的失真，更重要的是之後仍然可百分之百還原該媒體。This work presents a reversible data hiding method on encrypted audio files, where a data-hider, having no knowledge about the original content, tries to embed some additional data into the encrypted version of the content which was distributed from the content owner. A legal receiver, with the pre-negotiated decrypted key, can decrypt the encrypted content and get nearly the same version of the original medium. Moreover, if he/she has the pre-negotiated data-hiding key, the embedded data can be extracted, and therefore, the medium can be totally recovered. There are many kinds of media and some works targeting on hiding data into encrypted images have been proposed recently. Since human''s auditory system is more sensitive than human''s visual system, we apply a high order smoothness measurement to maintain the naturalness of a sound and let the content owner pre-calculate some necessary information for sound recovery, before encryption. With these two mechanisms, this work produces stego-audios of small quality degradation and has the capability to recover the original audios with zero error rate