利用特殊字元編碼的新資訊隱藏技術與其於網際網路上之應用

Abstract

隨著電腦和網路科技的發展，越來越多人透過網路來進行通訊，所以有必要保護網際網路上通訊訊息的安全性。以此，本論文提出了四種資訊隱藏的方法，用來對部落格、電子佈告欄系統(BBS)及電子郵件三種受歡迎的網路應用進行秘密通訊或文章驗證。 對於部落格，本研究利用不可視的特殊美國標準資訊交換碼(ASCII)控制碼組成的驗證訊號來識別部落格文章是否有被更改，達到文章驗證的功能。在電子公佈欄方面，本研究提出了兩種資訊隱藏的方法，分別是利用不可視的大五碼(Big-5)字元碼以及特殊的大五碼的空白碼來組成秘密資訊，此兩種方法透過電子公佈欄做媒介，都可用以進行祕密通訊以及文章驗證。最後，對於電子郵件，本研究提出了一個利用特殊八位元萬國碼(UTF-8)的空白碼的資訊隱藏技術，可用來驗證電子郵件，以偵測任何對受保護之郵件的惡意竄改。 上述所提應用都是利用這些特殊字元碼在各個應用平台上的不可視性，來隱藏秘密資訊而不被察覺，並將特殊字元編碼所構成的秘密訊息藏入原始文章當中，達到資訊隱藏的目的，而且所隱藏的秘密資訊皆可在之後正確地還原回來。 最後本論文也提供了相關的實驗結果，來證明所提方法的可行性。

With the progress of computer and networking technologies, communication via the Internet has become more and more popular nowadays, and so security protection of communication messages on the Internet has become a necessity. In this study, four data hiding methods for covert communication or article authentication are proposed for use on three Internet applications, namely, the blog, BBS, and email. For the blog, a new article authentication method based on one of the proposed data hiding techniques is proposed, which uses invisible ASCII control codes to construct authentication signals to verify whether a blog article is tampered with or not. For the BBS, two data hiding techniques are proposed. One uses invisible Big-5 codes, and the other uses special Big-5 space codes, for embedding message data imperceptibly. Each of the two techniques may be used to accomplish covert communication as well as BBS article authentication. Finally, for email, a data hiding technique via the use of special UTF-8 codes is proposed for webmail authentication, so that malicious tampering with a protected email may be found out. In all the applications mentioned above, the invisibility of the proposed special codes on appropriate platforms of Internet applications is utilized to achieve the aim of hiding data imperceptibly. A stego-article is generated by embedding the secret message information composed of the adopted special codes into the ends of the text lines of a cover article. The hidden secret information can be recovered correctly later. Experimental results showing the feasibility of the proposed methods are also included.