在資訊數位化與網路化的趨勢下，以網際網路傳遞訊息已非常普及。傳統方法採用加解密技術保護訊息，將明文資料轉換為無法識別的亂碼，僅讓擁有解碼金鑰的接收者可正確解讀資訊，因而確保了資料的安全性。然而，在資料傳遞的過程中仍有可能被截獲並且破譯。另外，傳輸加密資料在某些場合中是不被允許的，或是對於訊息的加密反而招致竊聽者或攻擊者的興趣。因此，如何加強資料傳遞的隱蔽性以確保訊息安全是項重要的議題。 本論文中提出在網路電話Voice over Internet Protocol (VoIP) 系統上的額外訊息傳輸機制。我們利用H.264/AVC視訊來達成有效的資料傳輸，另外記錄並告知接收端每單位資料量所需要的編碼宏塊數，讓接收者可檢視封包宏塊開始位置與前個封包的結束位置來判斷是否發生封包遺失以利重新傳遞。這些關於訊息大小與單位資料量所需宏塊數資訊將以G.729音訊封包傳送，同時減低了視訊處理的工作量。實驗結果將顯示本機制的實用性。 ;With the rapid growth of networking technologies and digital data, content transmission on the Internet has become a common operation. Traditionally, we encrypt the data to make them unreadable so that only the recipient who owns the decryption key can read the data successfully. Nevertheless, it is still possible that the eavesdropper may still intercept the data for further analysis. Besides, the application of cryptography in certain occasions may not be allowed. The encrypted data may even arouse the interest from the eavesdroppers. Therefore, how to transmit the data in a more secured way has been an important research issue. In this research, an additional data transmission scheme in Voice over Internet Protocol (VoIP) is designed. The H.264/AVC bit-stream is responsible for transmission the major data. The file size and the number of macroblocks for embedding a data unit are carried in G.729. By signaling the start and the end of macroblocks in H.264/AVC for embedding a data unit, we can know whether the packet lost has occurred and the retransmission can be applied. The experimental results will show the feasibility of the proposed method.
