Because of the increasing number of threats in the IoT cloud, an advanced security mechanism is needed to guard data against hacking or attacks. A user authentication mechanism is also required to authenticate the user accessing the cloud services. The conventional cryptographic algorithms used to provide security mechanisms in cloud networks are often vulnerable to various cyber-attacks and inefficient against new attacks. Therefore, developing new solutions based on different mechanisms from traditional cryptography methods is required to protect data and users' privacy from attacks. Different from the conventional cryptography method, we suggest a secure mutual authentication protocol based on the visual cryptography technique in this paper. We use visual cryptography to encrypt and decrypt the secret images. The mutual authentication is based on two secret images and tickets. The user requests the ticket from the authentication server (AS) to obtain the permission for accessing the cloud services. Three shared secret keys are used for encrypting and decrypting the authentication process. We analyze the protocol using the Barrows-Abadi-Needham (BAN)-logic method and the results show that the protocol is robust and can protect the user against various attacks. Also, it can provide a secure mutual authentication mechanism.

The IoT-enabled Smart Grid uses IoT smart devices to collect the private electricity data of consumers and send it to service providers over the public network, which leads to some new security problems. To ensure the communication security in a smart grid, many researches are focusing on using authentication and key agreement protocols to protect against cyber attacks. Unfortunately, most of them are vulnerable to various attacks. In this paper, we analyze the security of an existent protocol by introducing an insider attacker, and show that their scheme cannot guarantee the claimed security requirements under their adversary model. Then, we present an improved lightweight authentication and key agreement protocol, which aims to enhance the security of IoT-enabled smart grid systems. Furthermore, we proved the security of the scheme under the real-or-random oracle model. The result shown that the improved scheme is secure in the presence of both internal attackers and external attackers. Compared with the original protocol, the new protocol is more secure, while keeping the same computation efficiency. Both of them are 0.0552 ms. The communication of the new protocol is 236 bytes, which is acceptable in smart grids. In other words, with similar communication and computation cost, we proposed a more secure protocol for smart grids.

Scalar multiplication is a key operation on elliptic curves, and the implementation of scalar encoding is crucial to overall performance. Existing research on optimizing scalar encoding rarely considers parallel optimization for computing multiple single-scalar multiplications, because different scalars lead to different ordered calculation sequences, which makes it difficult to use SIMD and other techniques for parallel computing. In order to solve the problem of inconsistent scalar computation sequences, this paper proposes an efficient parallel single-scalar multiplication framework, named PSSM. By introducing a greedy sequence scheduling algorithm, this framework generates identical operation sequences when computing different scalars in parallel. Then, the method of constructing parallel modules with SIMD is given. The experimental results show that the common encoding methods—NAF, wNAF, and BNAF—implemented with PSSM achieve speedups of $5.98\times$, $5.69\times$, and $5.38\times$, respectively, on the i7-14700HX platform. The framework proposed can improve the implementation speed of existing NAF and its variant scalar encoding methods on CPU, which is significant for improving the performance of ECC-based cryptographic systems.