Consensus algorithms are the core technology of blockchain and a focus in the current distributed system research. The consensus algorithms are widely used in distributed systems, it has solved the decentralization problem. The traditional consensus algorithm needs the process of node legitimacy checking, identity authentication, and primary node view change, so the time cost of reaching an agreement between nodes is still exponential. In response to the problem, a lightweight consensus algorithm based on graph (LCAG) is proposed for the Internet of Things (IoT) in this paper, which is proposes an access control table, and reaches an agreement among nodes by calculating the probability of nodes in the control table, and reduces the time overhead of the reaching an agreement in distributed systems. We have carried out simulation experiments for the new algorithm, and the experiments show that: the new algorithm needs less time overhead than the classical Byzantine algorithm need, as well as Byzantine Generals problem (BGP), practical Byzantine fault-tolerant algorithm (PBFT) and directed acyclic graph (DAG) algorithm, and so on. The new algorithm can be applied to the devices of IoT, which have limited computing power.

The π ‐calculus is a basic theory of mobile communication based on the notion of interaction, which, is aimed at analyzing and modeling the behaviors of communication processes in communicating and mobile systems, and is widely applied to the security analysis of cryptographic protocol’s design and implementation. But the π ‐calculus does not provide seamless logical security analysis, so the logical flaws in the design and the implementation of a cryptographic protocol cannot be discovered in time. This paper introduces logical rules and logical proofs, binary tree, and the KMP algorithm and proposes a new extension of the π ‐calculus theory, a logical security analysis method, and an algorithm. The aim is to analyze whether there are logical flaws in the design and the implementation of a cryptographic protocol, to ensure the security of the cryptographic protocol when it is encoded into software and implemented. This paper presents the logical security proof and analysis of the TLS1.3 protocol’s interactional implementation process. Empirical results show that the additional extension theory, the logical security analysis method, and the algorithm can effectively analyze whether there are logical flaws in the design and the implementation of a cryptographic protocol.

The security analysis of protocols on theory level cannot guarantee the security of protocol implementations. To solve this problem, researchers have done a lot, and many achievements have been reached in this field, such as model extraction and code generation. However, the existing methods do not take the security of protocol implementations into account. In this paper, we have proposed to exploit the traces of function return values to analyze the security of protocol implementations at the source code level. Taking classic protocols into consideration, for example (like the Needham-Schroeder protocol and the Diffie-Hellman protocol, which cannot resist man-in-the-middle attacks), we have analyzed man-in-the-middle attacks during the protocol implementations and have carried out experiments. It has been shown in the experiments that our new method works well. Different from other methods of analyzing the security of protocol implementations in the literatures, our new method can avoid some flaws of program languages (like C language memory access, pointer analysis, etc.) and dynamically analyze the security of protocol implementations.