The agent of kdc producing key on the basis of users " individual character information , it adopts the digital watermark technology based on colored static digital picture to hide users " individual character information in the corresponding picture , use rsa algorithm to produce the public - key and private key , and utilize the diffie - hellman algorithm safe conveying to kdc system ; as to session key system , use algorithms of one - time key that put forward in text producing 个性化kdc代理采用基于彩色静止数字图像的数字水印技术将用户的个性信息隐藏在相应的图像中，对于公开密钥系统运用rsa算法产生基于用户个性信息的公开密钥私人密钥，并利用密钥交换算法? ? diffie - hellman算法将公开密钥安全的传送到kdc系统；对于会话密钥系统，运用本文提出的一次一密会话密钥产生的算法，利用单向散列函数的性质产生在既定范围内随着明文密文进行加密解密的需要而动态生成的一次一密的会话密钥。
Then , it introduce several cryptographic protocol based on elliptical curve , including diffie - hellman key switching , elgamal encryption and decryption , elgamal digital signature , ecdsa , etc . based on these , the author analyze kinds of security threat faced to 3g system and discuss the security rule and security objectives 然后介绍了基于椭圆曲线的几种密码协议，包括diffie ? hellman密钥交换， elgamal加解密， elgamal数字签名， ecdsa等协议。在此基础之上，分析了3g系统面临的各种安全威胁并对系统的安全原则和安全目标进行了讨论。
The main contributions of the dissertation are summarized as follows . ( 1 ) elliptic curve cryptosystems in optimal extension fields ( oef ) , including elgamal encryption algorithm , diffie - hellman key agreement scheme and elliptic curve digital signature algorithm ( ecdsa ) , are implemented , and a software package , which is applicable to microcomputers , is developed 本文所取得的主要研究成果是： ( 1 )完整实现最优扩域oef上的椭圆曲线密码体制，其中包括elgamal加密算法、 diffie - hellman密钥共享方案以及椭圆曲线数字签名算法ecdsa ，并且提供了相应的适合在微机上实现的软件包。
