Due to the advent of healthcare wireless medical sensor networks (HWMSNs) technology, the traditional model of medical treatment has been transformed. In HWMSNs environments, sensor nodes (e.g., wearable devices) collect medical data from patients and transmit them to doctors for diagnosis. Several certificateless aggregate signature (CLAS) schemes have been put forward to guarantee secure transmission of medical data and privacy of patients in HWMSNs. However, the utilization of a centralized key generation center (KGC) implies elevated risk of insecurity and privacy disclosure. Practical and destructive coalition attacks resulting from the collusion of an insider signer with a malicious KGC are difficult to resist. Therefore, a security-enhanced certificateless designated verifier anonymous aggregate signature (CL-DVAAS) scheme is devised to solve these problems. As introduced in the you only speak once (YOSO) model, an ever-changing, unpredictable committee replaces the role of the KGC for system initialization and key distribution. The serverless computing paradigm empowers the proposed scheme with excellent attack prevention and privacy protection capabilities. The proposed scheme is provably secure against various types of attacks in the random oracle model. Moreover, the performance evaluation and comparison illustrate that our scheme outperforms the state-of-the-art solutions.

Vehicular ad hoc network (VANET) enables a more efficient and secure traffic environment by integrating several emerging technologies. The technology of certificateless aggregate signature (CLAS) is widely utilized to guarantee secure communications in VANET. However, the legitimation of vehicles’ public keys cannot be verified effectively in existing CLAS protocols for VANET. Thus, a malicious key generation center (KGC) can masquerade as any vehicle and generate legitimate signatures. In this article, a reliable malicious KGC-resistant CLAS protocol, called RelCLAS, is proposed to eradicate this problem. RelCLAS solves the key escrow problem owning to the combination of registration-based encryption (RBE) and CLAS. Partial public keys selected by vehicles are stored in a key accumulator to prevent malicious KGC from forging valid signatures. Formal security proof demonstrates that RelCLAS satisfies the fundamental security requirements of VANET. Extensive simulations illustrate that RelCLAS is efficient, reliable, and feasible.

Vehicular ad hoc network (VANET) is an emerging technology that can significantly improve the efficiency of transportation systems and mitigate traffic accidents by exchanging traffic-related messages or announcements. Nevertheless, there has not been a consensus on how to generate, distribute, and validate trustworthy announcements in such an untrusted wireless environment. Security and privacy, inspiration mechanism, and resource integration are significant challenges for announcement generation and dissemination. In this paper, a secure and trustworthy announcement dissemination scheme is realized for location-based service (LBS) application in VANET. A blockchain-assisted vehicular cloud (VC) architecture is proposed to harvest underutilized heterogeneous resources of vehicles participating in VANET. Moreover, the technologies of blockchain and smart contract are adopted to classify vehicles into different levels automatically by bidding for bonuses. What’s more, vehicles can generate trustworthy announcements with the help of neighbor vehicles by adopting the technology of threshold signature. Meanwhile, the reputation of announcements is evaluated for trust management. Formal security analysis shows that the proposed scheme satisfies fundamental security and privacy requirements in VANET. Experimental results show that the proposed scheme is robust and efficient.

With an increasing number of IoT devices being deployed in healthcare, massive amounts of electronic health records (EHRs) are generated and shared in the cloud. To preserve data privacy, one promising data-sharing tool named attribute-based encryption (ABE) has been widely employed. However, it is a challenge to achieve flexible data sharing without loss of confidentiality when authorized users are dynamic. Another challenge is how to guarantee fleet data access time when resource-limited devices are used. In this article, a dynamic access policy ABE (DAP-ABE) system for EHRs in the cloud is proposed. The cloud server can update the access policy without sensitive information, while decryption keys of authorized users do not need to be updated. Authorized users enjoy approximately 0.07 ms data access by outsourcing the majority of the decryption overhead to the cloud server. Furthermore, a verification procedure is embedded in DAP-ABE to check the identities of patients in the data sharing stage, which ensures that no malicious user can upload invalid EHRs. Extensive experiments demonstrate the feasibility and efficiency of the DAP-ABE system.

Mobile crowdsensing enables people to collect and process a massive amount of information by using social resources without any cost on sensor deployment or model training. Many schemes focusing on the problems of task assignment and privacy preservation have been proposed so far. However, the privacy-preserving of requesters and task access control, which are vital to mobile crowdsensing, is barely considered in the literature. To address the aforementioned issues, a fine-grained task access control system for mobile crowdsensing is proposed. In particular, the requester can decide the group of task performers who can access the task by utilizing attribute-based encryption technology. T he untrusted crowdsensing platform cannot obtain any sensitive information concerning the requester or the task, while the qualified task performers are capable of retrieving tasks within 0.85 ms. Security analysis and experimental results are presented to show the feasibility and efficiency of the proposed system.

Return-Oriented Programming (ROP) is a technique which leverages the instruction gadgets in existing libraries/executables to construct Turing complete programs. However, ROP attack is usually composed with gadgets which are ending in ret instruction without the corresponding call instruction. Based on this fact, several defense mechanisms have been proposed to detect the ROP malicious code. To circumvent these defenses, Return-Oriented Programming without returns has been proposed recently, which uses the gadgets ending in jmp instruction but with much diversity. In this paper, we propose an improved ROP techniques to construct the ROP shellcode without returns. Meanwhile we implement a tool to automatically construct the real-world Return-Oriented Programming without returns shellcode, which as demonstrated in our experiment can bypass most of the existing ROP defenses.

The performance of wireless sensor networks (WSNs) is tightly coupled with the geometric environment in which sensors are deployed. In a practical environment, bottleneck regions, for example bridges, may exist due to the existence of physical obstacles or energy depletion. In this paper, we propose a load-balancing based optimal routing protocol (LORP). By finding the boundaries of holes in a sensor network with bottlenecks, LORP first identifies the bridges in the sensor field using our MACB algorithm. A centralized routing algorithm, "balance-first" routing is then employed to prolong the lifetime of a WSN with bottlenecks. Theoretical analysis prove that LORP can improve the load distribution among different bridges, increase the lifetime of a WSN, and enhance the quality of network services. This conclusion is reinforced in our simulation results.