File sharing is one of the most typical applications in P2P networks. Due to the problems of certificate management and key escrow, the traditional public key cryptosystems including PKI and ID-PKC are very difficult to be applied in the P2P networks. Identity authentication is always hard to be brought into effect, which brings some trust problems, such as free riding. The trust problems widely exist in such file sharing systems. In this paper, we research the applications with identity certification based on certificateless public key cryptography (CL-PKC), and build a file sharing system based on the JXTA platform in the P2P networks. The system implements key generation, identity authentication and file content authentication, verifies its feasibility and validity, and proves that it is so secure.

Now P2P network has been rapidly developed,but it faces a lot of security problems because of the structural characteristics.Network security has greatly hampered the development of P2P systems.Based on the respective analysis of the advantages and disadvantages of the traditional public key infrastructure(PKI),identity-based cryptography(ID-PKC) and certificateless public key cryptography(CL-PKC),proposes one kind of bidirectional authenticated and key agreement protocols in one domain and across multiple domains based on CL-PKC for hybrid P2P network.At last analyses its security.The scheme overcomes the problem of complicated management of PKI certificates and the key escrow of ID-PKC in P2P network.It speeds up the time of bidirectional authenticated and key agreement protocols,proved to be more efficient,and can better solve the security problems in hybrid P2P network.