Identity-Based Cryptosystems

本课题是为Shamir在Crypto '84上提出的基于身份的密码系统开发一种安全的实现方案，以实现邮件类型的密码通信和一些重要文件的数字签名。为了实现这样的密码系统，有必要研究一种新的可以创建两类秘密信息的单向函数，并利用它构造中心算法，这是我提出的概念。我们将离散对数问题与因式分解问题巧妙地结合起来，在基本概念的基础上展开研究，成功地解决了上述问题。然后根据可信中心给出的用户秘密信息和对方的公开身份信息生成公共信息，并对其进行修改，作为DES和FEAL等公共密钥密码系统的公共密钥。最后，上述公共信息可用于实现多种身份识别系统、签署重要消息和传递会议密钥。

This research project is to develop a secure realization scheme for the identity-based cryptosystem, of which concept is proposed by Shamir at Crypto '84, in order to realize a mail-type cryptographic communication and a digital signature for some important documents. For realization of such a cryptosystem, it is necessary to research a new one-way function which can creates two classes of secret information, of which concept is proposed by myself, and to construct the center algorithm using it. We developed our research being based on the basic concept to combine the discrete logarithm problem and the factoring problem ingeniously, and we could succeed to solve the above problem. Then the common-information is generated being based on the user's secret information given by the trusted center and the other party's public identity-information, and modifying it it is used as a common-key for the common-key cryptosystem such as DES and FEAL. Finally the above common-information can be used for implementing many kinds of identification systems, signing important messages and delivering conference keys.