Research Of Key Agreement Protocol Based On Certificateless Cryptosystem

Key agreement, which may protect the confidentiality and integrity of the data, is still oneof today’s cryptography research focuses. The early key agreement protocols can be achievedusing a public-key infrastructure or identity-based cryptography. There is a great deal ofcalculations in the traditional public-key cryptography, and there exists a key escrow problemin the identity-based cryptography. In order to overcome the above two disadvantages,Al-Riyami and Paterson presented the concept of certificateless public key cryptosystem in2003.Security of existing certificateless authentication key agreement protocol can beimproved. In this thesis, certificateless key agreement protocols are investigated concretely,that is,(1) two-party key agreement protocol based on certificateless;(2) tripartite keyagreement protocol based on certificateless;(3) authenticated group key agreement protocolbased on certificateless. The major contributions of the dissertation are as follows:1) We propose a new two-party certificatless key agreement protocol without pairing.Through the security analysis, the scheme satisfies known key security、 forward security、resistance to key compromise impersonation attack and unknown key sharing security.Through the efficiency analysis, the results shows that the user of the new scheme only needsfive point multiplication and two hashed to get the final session key. Compared with otherschemes with pairing, the efficiency of the scheme is higher.2) The authenticated tripartite key agreement protocol based on certificatelesscryptography proposed by Chen Jiaqi is analysised. The results shows that the protocol can notresist passive adversary attacks and meet the security attributes he stated. We improve theprotocol, and put forward a tripartite authenticated certificateless key agreement protocol. Ourprotocol is more security and efficient than that proposed by Chen, and can also be applied inthe plurality KGCs case.3) A one-round authentication asymmetric group key agreement protocol based oncertificateless is proposed. Through the security analysis, the scheme satisfies the securityattributes of the key agreement. Throughout the protocol process, the user only needsone-round communication, so efficiency of the protocol is very high.