【作者】 邢斌；

【导师】 侯春萍；

【作者基本信息】 天津大学 ， 通信与信息系统， 2007， 硕士

【摘要】 近年来,随着电话和传真机的广泛应用,通信安全隐患逐渐显露出来。对此,本文提出并实现了一种电话传真加密系统。针对电话和传真安全方面存在的问题,设计并实现了一种基于3DES(Data Encryption Standard)算法的电话传真加密系统。系统采用单片机作为中央控制单元;利用FPGA实现话音信号的加密解密;借助计算机的串行通信接口与系统相连,PC机运行用C++Builder编写的windows程序,用户可以通过此程序输入、修改密钥。系统密钥长度为256bit,可以按照规定的时间间隔跳变。采用该系统,能解决电话窃听所造成的信息泄露等问题,可用于各个领域的保密通话。经过实际应用,证明本系统设计合理,运行稳定可靠,符合电话安全产品化的要求。电话传真的加密都是通过转发加密后的电话和传真的数字信号实现的。电话加密是加密压缩后电话语音数字信号,在发送端,把电话话筒产生的模拟语音信号数字化、压缩、加密后通过调制解调器发送到接收端,接收端把接收到的数据解密、解压缩,最后转换为模拟语音信号驱动电话听筒。传真加密是加密传真的报文,传真调制解调器解调出传真的报文,加密后通过调制解调器发送到接收端,接收端解密报文后,把已解密的报文通过传真调制解调器发送给传真。目前,本系统已经设计完成,经公共交换电话网络(PSTN)测试,其传送话音清晰,传真图文清晰度不下降,并且密钥为256比特,每8秒钟跳变一次。更多还原

【Abstract】 In recent years, the telephone and the fax have been widely used. The communication security has gradually been a problem for their development. In this text, the design and application of a system that encrypt speech signal or the fax data is discussed.Aiming at the safety of telephone communication, a telephone encrypt system based on 3DES algorithm is described in this paper. The single chip is used as the central control unit and FPGA is used to encrypt and decrypt the data. The computer’s serial interface is used to download and change the secret key. The secret key of the system is 256-bit, and can be changed continuously. With this system, the problem of voice data being stolen can be solved. This telephone encrypt system has been implemented successfully and performs well, and can be used widely.The encryption of telephone and fax is achieved through transmitting the encrypted digital signal of telephone and fax. For telephone encryption, at the transmitter, analog voice signal, form microphone, is changed to digital signal and then it is compressed, encrypted and sent to the receiver by modem. At the receiver, information is decrypted and decompressed. And finally it is converted to the analog voice signal to drive the telephone handset. For fax encryption, data received by fax modem from fax is encrypted and tranmitted to the receiver. At the receiver, data is decrypted and sent to fax by fax modem.The system has been validated on the PSTN (Public Switched Telephone Network). It is indicated that the voice transmitted is clear and that the quality and the speed of the fax is ensured. It won’t affect the work of the telephone or the fax.更多还原