Study On (t,n) Threshold Group Signature Scheme Without Trusted Party

This thesis focuses on (t,n) threshold group signature scheme without trusted party based on elliptic curve and its application in mobile Ad Hoc networks.Adopting Shamir threshold secret sharing technique, a new (t,n) threshold group signature scheme without trusted party based on an improved elliptic curve digital signature algorithm is proposed. This new scheme has following advantages: The system has no trusted authority which can enhance the system's security and prevent from authority cheating, soften the precondition for threshold signature scheme and extend the extent of application of it; compared with existing control scheme, in the proposed scheme no trust center is needed for managing secret keys of signers, and no secure channel is maintained. So this scheme is easier in key management, significantly reduces the communication cost and computation cost, improve the system's efficiency and provides better adaptability. The thesis analyzes some commonly used attacks in detail to verify its security, including the effectual attacks of forgery attack, collusion attack etc. Results of the security analysis showed that it was impossible for the adversary to forge the individual signature and group signature. There was no secret information leakage during the total signature process. So this scheme makes good sense both in theory and practice.Mobile Ad Hoc networks are composed of mobile terminal nodes with wireless communication devices typically characterized by their multi-hop, temporary and non-trusted-center. Mobile Ad Hoc networks have their unique characteristics, such as energy constrained, dynamic network topology, multiple hop routing, and limited bandwidth .These characteristics make mobile ad hoc networks facing more serious threats of network security than centralized wireless networks. Now research on security in MANET is still in its infancy. Because of the inherent characteristics in the Ad Hoc wireless network, the centralized authentication services provided by CA in traditional networks is not suitable for this network. In this paper an identity-certification mechanism is introduced and so a new dynamic threshold group signature scheme suitable for MANET based on elliptic curve is proposed. It distributes the authentication services into the whole network, so that each individual node can potentially provide other trusted nodes with certification services. The scheme not only localizes the authentication service but also adapts to the scalability. At the same time, this scheme overcomes the limit to other distributed certification services which need trusted party at initialization phase in the system.