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Most of the existing cryptographic schemes, e.g., key agreement protocol, call for good randomness. Otherwise, the security of these cryptographic schemes cannot be fully guaranteed. Nonce-based cryptosystem is recently introduced to improve the security of public key encryption and digital signature schemes by ensuring security when randomness fails. In this paper, we first investigate the security of key agreement protocols when randomness fails. Then we define the security model for nonce-based key agreement protocols and propose a nonce-based key agreement protocol that protects against bad randomness. The new protocol is proven to be secure in our proposed security model.

Computationally lightweight and unconditionally secure key agreement protocols are very useful for secure communication in public networks. Recently, Guan et al. proposed a key agreement protocol whose security is based on the unpredictability of channel noise rather than computationally hard problems. These protocols are efficient, computationally lightweight, and unconditionally secure. However, authentication was not integrated into these protocols. In this article, we propose a new protocol with authentication capability that enables two nodes in the network to establish a secret session key for secure communication. It is more efficient, and it also preserves the lightweight and unconditional secure features of the key agreement protocols proposed by Guan et al. Therefore, it is more suitable for devices with limited computing power, such as sensors in Internet of Things (IoT).

A method of shared secret key distribution applicable to optical coherent multiplexing systems is proposed. It provides ways to detect the extent of eavesdropping. Detecting test factors and system design rules are suggested, and performance evaluation is performed in terms of mutual information between legitimate users and an eavesdropper. This scheme devises a new way of attaining secure optical communications without entirely relying on computational complexity.

Wireless sensor networks (WSNs) can take the advantages by utilizing the security schemes based on the concepts of quantum computation and cryptography. However, quantum wireless sensor networks (QWSNs) are shown to have many practical constraints. One of the constraints is the number of entangled qubits which is very high in the quantum security scheme proposed by [Nagy et al., Nat. Comput.9 (2010) 819]. In this work, we propose a modification of the security scheme introduced by Nagy et al. and hence the reduction in the number of entangled qubits is shown. Further, the modified scheme can overcome some of the constraints in the QWSNs.

An efficient ID-based authenticated key agreement protocol is proposed in this paper. This protocol provides known key security, perfect forward secrecy, key-compromise impersonation resilience, unknown key-share and imperfect key control. The computational complexity of the proposed protocol is only one elliptic curve point multiplications, one elliptic curve point addition and one operation of the pairing for each party, and the proposed protocol is efficient. The proposed protocol can be extended to address key escrow and key confirmation for application in reality.

Smart grid represents the future of power grid system. Apart from its various advantages on real-time monitor and control, it also brings many new security challenges. For example, users’ consumption data needs to be collected without violating their privacy. Moreover, authenticity and integrity of the data need to be protected during transmission. To solve these problems, many data aggregation schemes for smart grid have been proposed in the past few years. However, most of these schemes have employed expensive cryptographic functions, such as homomorphic encryption, making them impractical for the real use. In this paper, we introduce a lightweight privacy preserving data aggregation scheme for smart grid. A simple and innovative method is designed for the data aggregation phase. The benefit is that our proposed scheme is not only more efficient than the existing schemes, but also it achieves unconditional security in this phase. In other words, even if the adversary has unlimited computational power, he/she is unable to find out the consumption data for any individual user.