Traceable Digital Signature And Its Applications To Anonymous Authentication In Mobile Communication

In recent years, accompanied by the development of internet and mobile communication technologies, new security challenges are posed by emerging mobile internet which is consists of several heterogeneous subnets. Identity authentication is the key to the security of the mobile network. Digital signature is one of key techniques in information security, especially in the authentication, data integrity and non-repudiation. Digital signature has a wide range of applications, while the most important one is anonymous authentication in mobile internet. In order to protect the privacy of the users, anonymous digital signatures are used usually. Generallly, anonymous digital signatures include unconditionally anonymous signatures and traceable anonymous digntures. The unconditional anonymity of unconditionally anonymous signatures may be abused, while the traceable anonymous signatures can avoid these.This thesis mainly focused on the research of key technology of traceable anonymous signatures including anonymous proxy signature, threshold signature, and group signature. On this basis, this thesis further studies the applications of these traceable signatures to anonymous authentication in mobile internet. The main contributions are summarized as follows.(1) The problem of low efficiency in digital signature and verification is pointed out by analyzing Yu et al.’s anonymous proxy signature scheme firstly, and then an efficient and secure proxy signature with the properties of anonymity and traceability is proposed. Compared with Yu et al.’s scheme, the proposed scheme has higher efficiency; it is provably secure in the random oracle model based on the CDH assumption. (2) An anonymous proxy signature with revocation is proposed, and according to it, an anonymous roaming authentications scheme for mobile communication network is given. The proposed schemeis is proved to be existentially unforgeable in standard model against the adaptive chosen message attack; its security is based on the CDH assumption, and it not only achieves anonymity of mobile terminal, controllability and revocation of access permission, but also reduces the computational load of mobile terminal, which makes it more suitable for mobile terminal with limited power.(3) We present a security analysis of Liu-Huang threshold proxy signature scheme and demonstrate that their scheme does not satisfy proxy signer’s deviation and identifiability.t or more proxy signers can forge a valid signature that cannot be traced to themselves.An improved threshold proxy signature scheme is given based on Liu-Huang’scheme and the improved scheme achieves proxy signer’s deviation and identifiability.(4) In order to solve the problem that Camenisch-Stadler’s group signature scheme could not revoke members, a new member revocation scheme based on the Camenisch-Stadler’s group scheme is proposed, which allows the group manager to add new members or revoke old members flexibly and freely. When a member joins the group, the group manager issues member certificate to him/her, and other members need not update the key and certificate; when a member is revoked, the group manager only adds the anonymous identity of it to revocation list, and other members need not update the key and certificate too. Furthermore, the length of the signature and the computational effort for signing and verifying are independent of the number of the group members and the revoked members. The proposed scheme is more efficient than existing revocation scheme.(5) An anonymous access protocol on mobile internet is proposed, which is based on the group signature. This mechanism defined two visit mode of mobile termimal----self access and cross-domain access and the progress of each mode was described in details. The analysis shows that this protocol implements anonymous access to the mobile service and is correct, non-repudiation and traceable.