近年來由於個人通訊及網路科技快速的進步，造成人類生活上型態上重大的改變。在通訊方面，從早些年的有線電話，近期內快速的朝個人無線通訊發展，而無線通訊的標準也由於技術的改進而以日新月異的速度不斷的改良與更新。
　　在網路方面，近年來由於政府以及廠商大力的提倡全民上網，因此網路在很短的時間內便深入每一個家庭。而從最早期的窄頻撥接上網，到現在只需要少許的錢便可以寬頻到家，其變化與進步不可謂不大，透過寬頻網路的應用，使得人們得到更便利的生活，視訊會議便是其中一項偉大的應用。
　　這篇論文是希望從應用層的方向著手，透過由上層所付加的安全模組來達到『通訊安全』上的要求，並將之應用在已問世的視訊會議標準(如：H.323)上，並考慮與沒有由我們所發展的系統做溝通，以及降低資料量的加密運算等，藉此希望可以達成『安全和即時的通訊』這個目標。

　　Network communication techniques have been developed rapidly in recent years.Computer network becomes more and more popular and gradually turns into an essential part of human life. However, the convenience and the popularization of network accompany with latent threats. The network environment is open to every user and the information transmitted over network can be obtained without difficulty. For this reason, communication on network is insecure if there are not any security mechanisms.
　　With the mature development of data communication, it is a trend to integrate telecommunication and computer network. Voice communication over Internet is a new technology which many companies take great interest in. However, the voice signals are unprotected while transmission no matter over traditional telephone networks of computer networks. A secure voice system is necessary for achieving secure conversations.
　　This thesis proposes a secure voice communication system which supports transmission over PSTN and Internet. The proposed system applies cryptographic techniques to achieve private communication so that the video and voice signals are encrypted in the transmission channels. The key distribution protocol of the proposed system guarantees mutual identity authentication, key confirmation, and information security that other video conferencing communication systems do not provide. We also implement the system as software so that it is more flexible and practical for user, reduce the operations of encryption.

[1] Advanced Encryption Standard, http://csrc.nist.gov/encryption/aes/
[2] B. Schneier, “Applied Cryptography, 2nd Edition,” J.Wiley&Sons, Inc 1996.
[3] Carlton R. Davis, “IPSec: Securing VPNs,” The McGraw-Hill Companies, Inc.,2002.
[4] C.M. Chang, C.S. Laih, “The Design and Implementation of Secure Video/Speech
Communication System Over Internet,” 2002.
[5] D. Jones., Data compression and encryption algorithm, http://www.cs.uiowa.edu/~jones/compress/
[6] F. Cuervo and et. al., “Megaco Protocol Version 1.0,” RFC 3015, 2000.
[7] G. A. Spanos, T. B. Maples, “Security for real-time,” MPEG compressed video in distributed multimedia applications,” Proceedings of the 1996 IEEE Fifteenth
Annual International Phoenix Conference on Computers and Communications, 1996, pp. 72-78.
[8] H.323 Open source project: OpenH323, http://www.openh323.org/
[9] H.Cheng, Li Xiaobo, “Partial encryption of compressed images and videos,” IEEE
Transactions on Signal Processing, Volume: 48 Issue: 8, Aug. 2000 pp.2439-2451.
[10] ITU-T Recommendations H.261, “Video Codec for Audiovisual Services at p×64kbit/s,” 1993.
[11] ITU-T Recommendations H.263, “Video coding for low bit rate communication,”1998.
[12] ITU-T Recommendations H.264, “Advanced video coding for generic audiovisual services,” 2003.
[13] ITU-T Recommendations H.320, “Narrow-band ISDN visual telephone terminals to B-ISDN environment,” 2004.
[14] ITU-T Recommendations H.321, “Adaptation of H.320 visual telephone terminals to B-ISDN environment,” 1998.
[15] ITU-T Recommendations H.322, “Visual telephone systems and terminal equipment for local area networks which provide a guaranteed quality of service,” 1996.
[16] ITU-T Recommendations H.323, “Packet-based multimedia communications systems,” 2003.
[17] ITU-T Recommendations H.324, “Terminal for low bit rate multimedia communications,” 2004.
[18] ITU-T Recommendations V.70, “Procedures for the simultaneous transmission of data and digitally encoded voice signals over the GSTN, or over a 2-wire leased
point-to-point telephone type circuits,” 1996.
[19] M. Arango and et. al., “Media Gateway Control Protocol (MGCP) Version 1.0,”RFC 2705, 1999.
[20] M. Handley and et. al., “SIP: Session Initiation Protocol,” RFC 2543, 1999.
[21] NBA FIPS PUB 46-1, “Data Encryption Standard,” National Bureau of Standards, U.S. Department of Commerce.
[22] R. Naujoks, M. Gustafsson, “A public key encryption system for defective data transmission,” Proceeding of Seventh IEEE International Workshops on Enabling Technologies: Infrastructure for Collaborative Enterprises, 1998, pp.346-351.
[23]賴溪松，韓亮，張真誠， “近代密碼學及其應用”，松崗電腦圖書資料股份有限公司，1995。
[24] 陳培德，陳坤元，賴溪松，王文能，“加速實現AES 密碼器的方法”，第十一屆全國資訊安全會議論文集。
[25] 賴溪松，邱榮輝，林祝興，盧而輝，張克章，“電子簽章 應用與實習”，旗標出版社，2004。
[26] 戴顯權，陳瀅如，王春清，“多媒體通訊”，紳藍出版社，2002。