ABSTRACT Graph neural networks (GNNs) have been widely applied to various machine learning tasks, particularly in social network analysis and healthcare. Meanwhile, privacy concerns in GNN have attracted increasing attention. In graph‐level classification tasks, differential privacy mechanisms are commonly employed to protect sensitive information, often implemented through stochastic gradient descent. However, the addition of excessive noise can significantly degrade model performance. In this paper, we propose layer‐adaptive differential privacy (LADP), an adaptive noise injection mechanism designed for graph classification tasks. In the proposed mechanism, the noise addition process is separated into the stages of node feature aggregation and whole‐graph feature update. To reduce the impact of noise on model utility, adaptive noise is added to each layer individually, allowing for more precise gradient control across the network. We evaluate our method on several public benchmark datasets. Experimental results show that LADP achieves higher classification accuracy than existing approaches under comparable privacy budgets.

Summary Object detection in crowded scenes involves various difficulties, such as small objects, occluded objects, and insufficient features. Existing models for crowded object detection often focus on only one detection difficulty, and they are too large to be applied in practice. To address the diverse challenges of object detection in crowded scenes, we construct a lightweight crowded object detector called MBB‐YOLO, which contains several modules for comprehensive improvement. To improve the network's ability to extract fine‐grained features, we use SPD‐Conv and the proposed MS‐Conv to replace the strided convolution in the network. An bi‐branch multi‐scale convolution attention (BMCA) module is proposed to aggregate multi‐scale contextual information. We also propose boundary‐NMS to better identify proposal boxes from different objects, which reduces suppression errors caused by object occlusion. MBB‐YOLO achieves 87.6% AP and an inference speed of 78.8 FPS on the CrowdHuman dataset, which surpasses other mainstream lightweight object detectors.

With the proliferation of the Internet of Things (IoT), access control has become particularly important in protecting data security. However, traditional access control models have limited capabilities in addressing challenges such as single points of failure, coarse-grained access control, and insufficient security in distributed environments. To tackle these challenges, we propose DTSAC, a smart contract-based access control with distributed delegation and dynamic trust management. This model utilizes blockchain for the decentralized delegation of capabilities and distributes delegation relationships across multiple delegation trees to enable fast revocation of capabilities. In addition, we design a dynamic trust assessment mechanism between the delegator and the delegatee to more comprehensively evaluate the credibility of the subject. Finally, a functional prototype of the DTSAC is successfully deployed on the public Sepolia Ethereum testnet. The experimental evaluation is conducted to verify the feasibility and effectiveness of the proposed model.

Summary In order to protect private data in edge computing system and ensure that ciphertexts encrypted under different keys can be processed in the cloud, we propose a privacy protection protocol for edge computing, which is based on blockchain technology and multikey fully homomorphic encryption (MFHE). By constructing a Merkle hash tree and saving the Merkle root node to the blockchain, the integrity of the data in edge nodes is protected. For the data with high computational complexity in edge nodes, the GSW fully homomorphic encryption scheme is employed to process the encrypted private data of a single edge node by the CMS. The LinkAlgo algorithm is applied to link different keys by the relation between them, which enables the CMS to process the encrypted private data of multiple edge nodes. The security analysis and performance evaluation of the proposed privacy protection protocol show that our protocol has high security and good efficiency.

The Internet of Things (IoT) is an emerging technology and expected to provide solutions for various industrial fields. As a basic technology of the IoT, wireless sensor networks (WSNs) can be used to collect the required environment parameters for specific applications. Due to the resource limitation of sensor node and the open nature of wireless channel, security has become an enormous challenge in WSN. Authentication as a basic security service can be used to guarantee the legality of data access in WSN. Recently, Chang and Le proposed two authentication protocols for WSN for different security requirements. However, their protocol cannot provide proper mutual authentication and has other security and functionality defects. We present a three-factor user authentication protocol for WSN to remove the weaknesses of previous protocols. The security of the proposed protocol is analyzed, and the security, functionality and performance of our protocol are compared with other related protocols. The comparison results and simulation results by NS-3 show that the proposed protocol is robust and energy efficient for IoT applications.

ABSTRACT With the development and maturation of the wireless communication technologies, the wireless sensor networks have been widely applied in different environments to acquire specific information. The wireless medical sensor networks (WMSNs), as a professional application of the wireless sensor networks in medicine, have attracted more and more attention because of its potential in improving the quality of healthcare services. Through the WMSNs, the parameters of patients' vital signs can be gathered from the sensor nodes equipped on the body of the patients and then can be accessed by the healthcare professionals by using a mobile device. By reason of the open feature of wireless communication, how to guarantee secure communication becomes an important issue. On the other hand, because the vital signs parameters are sensitive to the patients' health status and no one wants to reveal it to the others except the healthcare professionals, the protection of patients' privacy becomes another key issue for WMSNs applications. User authentication protocol with anonymity is the most basic and commonly used method to resolve the security and privacy issues of WMSNs. Recently, He et al. proposed an enhanced authentication protocol for healthcare applications using WMSNs to protect the security and privacy problems. However, we find that their scheme is incorrect in authentication and session key agreement phase. Besides, their scheme has no wrong password detection mechanism, which will not only waste the unnecessary computation and communication costs, but also may deduce the denial of service problem. In this paper, the biometric is introduced as the third authentication factor, and a new user anonymous authentication protocol based on WMSNs is designed so as to remove the drawbacks of the protocol of He et al. Compared with previous protocols, the new presented protocol enhances the security and also keeps the computation efficiency. Copyright © 2015 John Wiley & Sons, Ltd.

Abstract As the fast growth of multimedia information, the security of multimedia systems is becoming a rather important topic nowadays. Multimedia systems are often suffering attacks when users access the information and online services. Because of the excellent features of the biometric, many biometric‐based three‐factor remote user authentication schemes have been proposed to provide high level of security for different network‐based application systems. Recently, An pointed out the weaknesses of Das's three‐factor remote user authentication scheme and proposed an improved biometric‐based three‐factor remote user authentication scheme. An's scheme improves the security problems of previous schemes while keeping the efficiency. However, after detailed analysis, we find that An's scheme exists some weaknesses such as vulnerable to denial‐of‐service attack and forgery attack, cannot detect unauthorized login quickly, and does not provide session key agreement. In order to provide high level of security for multimedia systems, we design a robust three‐factor remote user authentication scheme with key agreement using elliptic curve cryptosystem. Copyright © 2014 John Wiley & Sons, Ltd.

Authentication protocols are the basis of security in many distributed systems. NSSK protocol is an early classical authentication protocol, which is the basic model of Kerberos protocol widely applied. This paper introduces NSSK protocol, and analyzes its security, and proposes an improved NSSK protocol which is formally proved with BAN logic. The proof shows that the improved NSSK protocol can accomplish its security goal and resist some attacks, such as replay and cheat.