利用數位通信序列作音訊資料隱藏

Abstract

隨著全球邁入網際網路發達與3C（電腦、通訊、消費性電子）產品普及的數位時代，傳播與下載數位資訊變得十分方便。然而，科技的進步雖然提昇了工作效率，卻令盜版及違法使用日益猖獗，因此，資料隱藏技術顯得格外重要，其中數位浮水印可以用來保護多媒體的智慧財產權；數位指紋則可以提供證據找出違法的拷貝者或傳播者。 本篇論文提出一項音訊資料隱藏技術，視數種數位的通信序列為祕密寫作的信號，將欲隱藏的二元資訊加入秘密寫作信號中，再一起藏入原來的音訊，且不被人耳察覺。通信序列包括跳頻展頻序列：Welch-Costas 陣列、完全互補碼與二元零相關區域序列。此方法具有自我同步的特性，且利用對應的匹配濾波器重新找回藏入的位元。進一步引入音訊秘密共享的概念，同時使用多組特定序列當作秘密寫作信號，更能增加偵測位元的正確率，使錯誤率降至0.1以下，達到資料隱藏的目的。 接下來，我們會介紹音訊及光學的密碼系統，兩組系統均以干涉特性為基礎，屬於秘密共享的範疇，分別共享音樂或靜態影像。這些共享資料不僅提供良好的隱密性，更保有原始資料的品質，讓人們不會懷疑其真偽。解密方式也不再侷限於使用電腦，透過收聽喇叭或耳機能解開音訊加密，而Mach-Zehnder干涉計則能解開光學加密。

The whole world has evolved into a 3C (including computer, communication and consumer electronics products) age with booming Internet connectivity. By following progress of the digital age, it is easy for people to distribute and download digital files which have caused serious problem of piracy in media distribution. Therefore, data hiding techniques become important in particular. Digital watermarking scheme is used to protect the intellectual property rights of multimedia and digital fingerprinting is applied to provide an evidence for finding illegal users. In this paper, we propose an audio data hiding technique which takes several digital communication sequences, including Welch-Costas (W-C) arrays, complete complementary (CC) codes and binary zero correlation zone (ZCZ) sequences, as the steganographic signals. The binary information is embedded into the steganographic signal that is subsequently hidden to the host signal and the watermarked signal is inaudible for human hearing. The method is self-synchronizing and allows us to recover embedded bits with a corresponding matched filter. Furthermore, we use more than one series of the communication sequence to implement the embedding algorithm. This can reduce the error rate below 0.1 errors. Next, audio and optical cryptographic schemes based on interference property of waves are introduced. Two schemes are also secret sharing schemes in which shares are music or images and are not suspect to human perception. They guarantee perfect privacy as well as high quality. It is stated that using computer is not the only way to decrypt the message. For audio cryptographic scheme, we can play two shares on a stereo system, either players or headphones. For optical cryptographic scheme, the Mach-Zehnder interferometer is used as a decryption machine.