Enhanced ID-based authenticated key agreement protocols for a multiple independent PKG environment

In 2005, Lee et al. proposed an ID-based 2-party key agreement protocol between users whose private keys were issued by independent PKGs that do not share any system parameters. This work was the first kind that assumes completely independent multiple PKG environment. However, Lee et al. protocol has a flaw that allows attackers to impersonate others without knowing their private keys. In this paper, we propose a modification to the protocol of Lee et al. that prevents impersonation attacks. We also show a simple technique that can improve the efficiency of tripartite key agreement protocol of Lee et al. We also provide analysis of the security and efficiency of the proposed protocols.