A novel pairing-free certificateless authenticated key agreement protocol with provable security

Recently, He et al. (Computers and Mathematics with Applications, 2012) proposed an efficient pairing-free certificateless authenticated key agreement (CL-AKA) protocol and claimed their protocol was provably secure in the extended Canetti-Krawczyk (eCK) model. By giving concrete attacks, we indicate that their protocol is not secure in the eCK model. We propose an improved protocol and show our improvement is secure in the eCK model under the gap Diffie-Hellman (GDH) assumption. Furthermore, the proposed protocol is very efficient.