Secondly, we make a contrast of different schemes with the PSMLAC in Table I. As all of these schemes have realized user privacy protection in smart grid, we mainly pay attention to message authentication, traceability of broken SM, dynamic user, complex statistical analysis, and the existence of TTP. As Garcia and Jacobs [7] and Chen et al. [20] make use of Paillier encryption, C cannot verify the validity of the received message; and as what C received are all consumption data in encrypted form, C can only make a simple statistic analysis of the real-time electricity use information, such as the sum of all consumption data. Zargar and Yaghmaee [17] and Chen et al. [20] both have the properties of traceability of broken SM and dynamic users; however, their securities rely on the security of TTP. If the TTP colludes with the adversary
or is compromised by the adversary, the user even enjoys
no privacy. We observe that Liu [18] can achieve the same
functions as our PSMLAC. However, Liu [18] uses the linkable
ring signature, and the length of signature in his scheme
is O(N), where N is the number of public keys that a user
uses to make signature.