Research On Multi-party Key Agreement Protocol

With the fast development of computer technology and the prosperous of the Internet, how to ensure information security in open network has become a research field whose key technology is cryptography.Key agreement protocol produces a secret session key in a information interactive way, while participants are in an uncertain security network, guaranteeing the security of communication data with symmetric encryption mechanism. It's a foundation of many advanced protocols in cryptography.Two design focuses of security key agreement protocol are security and validity.For the security, the basic properties of key agreement protocol are Known-Key Security, Key Control Property, Resist Key Leakage Attack, Perfect Forward Secrecy and Key Sharing. For the validity, we have to consider the number of rounds of communication and the amount of computation.According to the number of participants, the key agreement protocol includes three types, two parties key agreement protocol, three parties key agreement protocol and multi-party key agreement protocol. In this passage, we mainly research the multi-party key agreement protocol.Our research results are as follows:Firstly, we introduce the existing multi-party key agreement protocols, analyse communication complexity and computational complexity about them, and discuss whether they can be used for dynamic changes of the members.Secondly, we propose a novel multi key agreement scheme that is PKI authentication based on elliptic curve. We use a secure one-way function instead of bilinear pairing to construct that scheme and make a discussion with security and validity.Finally,with block chaining technique,we propose a new scheme of multi-party key agreement protocol based on block chaining. The protocol combines with block chain storage to decrease the reliance on third party trusted centers, which is only used to the distribute public and private key, prevent the center from doing evil and make the protocol process more secure and transparent.