Research On Key Problems In Identity Based Public Key Cryptography

The challenge today in developing secure systems based on public key cryptography is not only choosing appropriately secure algorithms and implementing these, but also developing an infrastructure to support the authenticity of a user's public key. In the traditional public key infrastructure (PKI), certificates are used to provide an assurance of the relationship between public keys and the identities that hold the corresponding private keys. However, a PKI faces many challenges in practice, such as the scalability of the infrastructure and certificate management. To address the shortcomings of PKI and to simplify key management, Shamir proposed the notion of identity-based public key cryptography (ID-PKC) in 1984. In ID-PKC, the public keys are derived from the users'identities, such as a username or an e-mail address. The certificate is not required to authenticate the public keys of users. ID-PKC is another valid way to authenticate the user's public key. Compared with PKI, ID-PKC has advantages in key management.Shamir proposed a first identity based signature scheme when he introduced the notion of ID-PKC. But the research on identity based encryption has less progress. Until 2001, Boneh and Franklin proposed a practical and secure identity based encryption using Weil pairing, which makes the ID-PKC become a research hot again. Since then, many identity based cryptosystems have been proposed. However, ID-PKC still has some open problems such as key escrow, key revocation, security model building problem and so on. It is important to research and solve these problem not only on theory but also on practice. This paper focuses on these problems, proposes some valid schemes and gets some research results. The main researches in the paper are as follows:1. We have a research on the key escrow problem in ID-PKC and point out the certificateless public key cryptography CL-PKC which has the advantages of ID-PKC can overcome the key escrow limitation in ID-PKC. A new certificateless public key encryption scheme is proposed. In this paper, we propose a new CL-PKE scheme which is based on the nice algebraic properties of Weil pairing and proof the security of the scheme formally in the random oracle model. Different from existing series model, the new scheme works in a kind of parallel model. MapToPoint function is not involved in the scheme which is hard computed. In the encryption algorithm no paring computation is required and the proposed scheme is more efficient on performance than the existing schemes. Hence, the proposed scheme has important practical value.2. We have a more research on certificateless authentication key agreement. CL-PKC...