隨著網路頻寬的成長，對於影音多媒體串流的需求也隨之增加，隨選視訊系統 (VOD) 的發展也被認為是下一波網際網路應用的主流。由於數位多媒體檔案在電腦上具有複製容易、散佈快速的特性，所以目前的社會上販賣非法複製、拷貝多媒體檔案的情況日益猖獗，加上現今網路的普及，使用者可以利用點對點傳輸網路 (P2P) 或FTP之類的方法來散佈多媒體檔案，使得擁有版權和著作權的廠商對於多媒體檔案的管理愈來愈困難。相同的情形在傳統的隨選視訊系統上也會出現的，雖然隨選視訊系統已經行之有年且各式應用於其上的演算法，例如：快取伺服器 (Cache Server) 的快取替換 (Cache Replacement) 演算法，影片廣播 (Video Broadcasting) 的演算法，也都發展至一成熟且完整的架構，但在實際的應用上尚有一段距離，因為應用在實際就會產生商業上或其它層面的考量，對於影片的管理在傳統的隨選視訊系統上並無一確實而有效的方法，如此一來影片的擁有者便要面臨到檔案被任意複製和非法傳播的風險。 本文提出了一結合Kerberos使用者認證機制及數位著作權管理(Digital Rights Management) 的隨選視訊系統。系統使用認證伺服器 (Authentication Server) 來管理所有使用者的資訊，利用Kerberos中門票的觀念來對合法的使用者核發門票，使得使用者可以持此門票來向各個伺服器來要求服務及其欲觀看的影片。在影片的管理上我們使用對稱式加密的方法將影片加密，然後利用DRM中License的技術，使得播放器可以藉由License中獲得解密的金鑰以及其中的規定來限制存取的權限及方法。最後，我們利用熱門廣播法來實作出整套系統，並且實際在網路上播放以測試其效能。 As the growth of bandwidth of Internet, the demand of media streaming is increasing as well. The development of video on demand system is considered as next main application on the internet. Due to the characteristics of copying easily and distributing rapidly, there are many illegal copies sold nowadays. Users can get Internet everywhere, they can distribute media files by P2P network or FTP and so on. The rights holders are losing their ability to manage media files. The traditional VOD system has the same case. Although VOD has applied for simulation for many years, the variant algorithms of video on demand (for example: cache replacement algorithms of cache server, algorithms of video broadcasting) have developed to a mature and complete architecture, but most of them are focused on the simulation. Because we have some others considerations in applying on commerce or other aspects, it still has a distance to the practice of application. Content owner may take the risk of copying and distributing illegally. Thus we need to solve the problems below: The first problem is the management of users: the system allows only the legitimate users to log in to watch the movies that they want. The offered information when the users login must prevent from malicious eavesdrop or interception. The second one is the management and the protection of the video copyrights. When users receive the video, we have to manage and protect the copyrights. The video owners have to take the risk of copying video arbitrarily and distributing illegally by users without any protection. There must be an approach to protect the copyrights of video. We proposed a VOD system with Kerberos user authentication mechanism and digital rights management. By using authentication server, we can manage all information of users. With the concepts of tickets in Kerberos, we grant tickets to the legitimate users. Users who get the tickets can request the services and the videos that they want to watch. We encrypt the videos using symmetric encryption algorithm to manage videos. Then we use the license technique in digital rights management such that the video player can get the key to decrypt the video from license and the rules to limit access rights. Finally we implement the system with hot-video broadcasting and test it on real network.
