Some Special Classes Of Identity-based Proxy Signature Scheme,

Since Diffie and Hellman proposed the concept of public key cryptography. Public key cryptography has been developing quickly. Digital signature which is an important part of public key cryptography has been researched in a broad and deep way. Digital signature is concerned so widely. Because it has the following features, confirm the authenticity of identity, to ensure the authenticity and non-repudiation of information.According the way of getting keys, digital signature can be divided into certificate based signature and identity based signature. Shamir first introduced identity based cryptosystem. In this system, public and private keys contain users'identification information. So, it avoid providing the certificate to verify whom a user's public key belongs to. It is precisely because identity based cryptosystem reduces the reliance on the certification. Identity based signature becomes a research hotspot.Proxy signature which is a sort of important digital signatures, first introduced by Mambo et al. in 1996. Identity based proxy signature is such kind of signature that combines identity based cryptography and proxy signature. This paper mainly discusses the development and current situation of several special identity based proxy signatures which generally exist the following problems. Proxy signers can forge valid signatures without being authorized. Attackers can compute or forge users' valid signing keys easily. The scope of the schemes that have been researched is limited. To solve these problems, this paper designs a identity based proxy ring signature scheme and two identity based threshold proxy signature schemes. Meanwhile, considering the research in identity based signatures based on large integer factoring is poor, this paper carries out research and exploration on this aspect, and proposes a identity based signature scheme and a proxy signature scheme using quadratic residues. The main results are as follows:1. Analyzing an identity based proxy ring signature scheme, the results show that the private key of original signer can be divulged easily and proxy signers can forge valid proxy ring signatures. A new secure scheme is proposed which is based on the original scheme, extending a single original signer into a ring. 2. This paper proposes two identity based threshold proxy signature schemes. In one scheme, proxy signers can generate the signature anonymously. The other scheme is constructed under the standard model.3. Analysis of a identity based signature scheme based on quadratic residues is given in this paper, pointing out attackers can forge valid signing keys through two ways. The scheme has the problem of low efficiency at the same time. A new signature scheme and a proxy signature scheme based on quadratic residues are proposed which are based on the original scheme. The new schemes solve the problems in the original scheme efficiently.