Identity-based Cryptography And Its Applications

Identity-based cryptosystem is first proposed by Shamir in 1984. Shamir suggested the information which can be a symbol of user's identity be used as the public key in the cryptosystem , such as the user's name or email address.The main practical benefit of Identity-based cryptosystem is greatly reducing the need for, and reliance on, public key certificates. Because of the applications of the bilinear pairings, IBC system improved rapidly. Since Boneh and Franklin proposed the first secure and practical Identity-based encryption using Parings Technique in 2001, IBC system gained much production, which has been an active hotspot direction in cryptography field. However, there are some problems about IBC, such as identity authentication, private key distribution, key escrow and so on. Aiming at these problems, this thesis studied IBC system deeply . We use Elliptic Curve Cryptography , bilinear mapping, difficult assumption, hash function as basic knowledge tools.At first, the basis condition and the framework of IBC is introduced in this paper, The Identity-based Encryption based on bilinear pairings which is proposed by Boneh and Franklin(BF-IBE)is analyzed in detail. And We compare the existing categories of IBE design about it's safety and efficiency .A new efficient scheme constructed is based on a new difficult assumption (decision weak bilinear Diffie Hellman assumption),and this scheme is proved secure against adaptive chosen ciphertext attack.Key-escrow is a problem in Identity-based crytosystem. The former authors mainly used two ways to solve this problem: the one is giving the job of generating key to multi-entities. The method changes the situation that a key generator center is trusted absolutely. The other one is that the user is concerned with the process of generating the key. The private key includes some information which can only be known by user then not any key generator center need be trusted. The thesis proposed a new Key-escrow scheme based on HIBE scheme and twice registration and the former two ways are fused well.It is more reliable than other ways.Email is one of the most widely used and the most important applications on the Internet, it is simple and speedy, convenient for people to communicate with each other. Because the Internet is an open system, the Email message on it would be attacked here and there. To prevent the Email from all kinds of attacks, secure Email solutions should be proposed and used in specific fields.This paper introduce the schemes and ways about secure email nowadays. Moreover, on the basis of the idea of two new schemes above, a more security email is proposed and realized.