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Machine-type communication (MTC) is a very important application of the Internet of things. It has a vast market and application scenarios. However, supporting a large number of low-power devices transmission is an important issue in long-term evolution/long-term evolution advanced (LTE/LTE-A) networks. Specifically, when a large number of machine-type communication devices (MTCDs) with low-power consumption requirements simultaneously request access to the LTE/LTE-A networks, each MTCD needs an independent complete access authentication process with core network, which may cause a serious signaling congestion in the core network. To solve this problem, in this paper, we propose a novel group authentication protocol with privacy-preserving for MTC in the LTE/LTE-A networks. The proposed protocol cannot only simultaneously authenticate a group of MTCDs and minimize the signaling overhead but also provide robust privacy-preserving for each MTCD (including anonymity, unlinkability, and traceability). In particular, our scheme can avoid denial of service attack by filtering some illegal devices in the first four procedures of the mutual authentication. Moreover, our scheme fulfills all the security requirements of the MTC in LTE/LTE-A networks. In addition, the formal verification by the ProVerif tool shows that the proposed scheme is secure against various malicious attacks, and the performance evaluation indicates that it achieves outstanding results in terms of signaling and computation overhead.

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A single-source ZnTi-layered double hydroxide precursor was used to prepare single phase Zn2TiO4. This approach involves two steps: the calcination of a ZnTi-layered double hydroxide precursor and selective leaching zinc oxide from the resultant calcined products. The materials were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) thermogravimetric and differential thermal analysis (TG-DTA), transmission electron microscope (TEM), surface area measurement and UVvis diffuse reflection spectroscopy. The results indicated that a single phase Zn2TiO4 could be successfully obtained from a ZnTi-layered double hydroxide precursor at a relatively low temperature in short calcination time. The TEM and SEM show that the diameter of Zn2TiO4 particles prepared at 900 degrees C is in the range of 20-100 nm and smaller than that prepared by the solid-state method. UV-Vis diffuse reflection spectroscopy demonstrates that the material has an energy bandgap around 3.7 eV.