Security analysis and improvements of hierarchical identity based authenticated key agreement scheme

The security of hierarchical identity based authenticated key agreement scheme which was proposed by CAO et al. (2014) is cryptanalyzed. First, it is pointed out that the scheme is not completely secure against the basic impersonation attack. Then, the process and the reasons of the attack are described. Finally, an improvement scheme to mend the security leaks is proposed based on the hierarchical identity based encryption (BONEH et al.2005). The security proof of the proposal is presented in the BJM model. The computation efficiency of the proposed scheme is nearly equivalent to the CAO et al.'s.