| Popis: |
In the above article [1], there is an inconsistency in defining the equation $HV$ in the login phase and mutual authentication phase as shown in Figs. 3 and 5, respectively. In the Cloud Server $CS$ of Fig. 3, $HV$ is equal to $h\left(RV_{i} \oplus CID_{i} \| HS\right)$ in which $RV_{i} \oplus CID_{i}$ is equal to $h\left(VID_{i}\right)$ as described in Fig. 2 and $HS=h\left(S_{i, t}^{\prime}\right)$ as shown in the previous line of equation $HV=h\left(RV_{i} \oplus CID_{i} \| HS\right)$ . Then, in the User $U_{i}$ of Fig. 3, $V K_{x}=h\left(VID_{i}^{*} \| h\left(S_{i, t}^{\prime}\right)\right) \oplus K_{x}^{\prime}$ in which the value of $V K_{x}$ is equal to $HV \oplus K_{x}$ as derived in the Vehicle $V_{i}$ of Fig. 5. However, the $HV$ in the previous $V K_{x}$ of Fig. 3 is wrong, as the consequence, it should be $V K_{x}=h\left(h\left(VID_{i}^{*}\right) \| h\left(S_{i, t}^{\prime}\right)\right) \oplus K_{x}^{\prime}$ in order to make it consistent with the previous definition of $HV$ in the Cloud Server $CS$ of Fig. 3. Therefore, the $HV^{\prime}= h\left(VID_{i} \| HS^{\prime}\right)$ in the Vehicle $V_{i}$ of Fig. 5 should be modified into $HV^{\prime}=h\left(h\left(VID_{i}\right) \| HS^{\prime}\right)$ . |
