Trust establishment among vehicles is essential for vehicular ad hoc networks (VANETs) as it directly impacts the security and privacy of vehicular communication. Many trust estimation approaches have been introduced, however, they often suffer from ensuring effective trust for vehicles. In fact, existing approaches do not involve all malevolent properties of vehicles in trust computation and can not properly handle the content tampering attack, which eventually affect the accuracy of the estimated trust. Moreover, most of them do not consider the uncertainty of VANET arising from vehicles’ mobility, their inaccurate/incomplete data dissemination, and the wireless communication channels, which also affects the reliability of the trust estimation. To address these limitations, this paper proposes a fuzzy logic-based approach to estimate vehicles’ trust. The new approach considers three trust factors, captured by fuzzy sets, to model malicious properties of a vehicle. Further, it involves a new data-centric parameter to capture the impact of content tampering on trust evaluation. In addition, the new approach includes an inter-edge trust transfer mechanism to carry forward a vehicle’s trust when it switches to a new edge server to ensure a seamless operation in VANETs. We evaluate the performance of the proposed scheme against the state-of-the-art approaches using both synthetic and real-world datasets. The experimental results reveal that it outperforms existing schemes in detecting malicious vehicles with higher recall, precision, and accuracy. Further, the new scheme reduces end-to-end delay and messages per data packet compared to other schemes.

Trust estimation of vehicles is vital for the correct functioning of Vehicular Ad Hoc Networks (VANETs) as it enhances their security by identifying reliable vehicles. However, accurate trust estimation still remains distant as existing works do not consider all malicious features of vehicles, such as dropping or delaying packets, altering content, and injecting false information. Moreover, data consistency of messages is not guaranteed here as they pass through multiple paths and can easily be altered by malicious relay vehicles. This leads to difficulty in measuring the effect of content tampering in trust calculation. Further, unreliable wireless communication of VANETs and unpredictable vehicle behavior may introduce uncertainty in the trust estimation and hence its accuracy. In this view, we put forward three trust factors - captured by fuzzy sets to adequately model malicious properties of a vehicle and apply a fuzzy logic-based algorithm to estimate its trust. We also introduce a parameter to evaluate the impact of content modification in trust calculation. Experimental results reveal that the proposed scheme detects malicious vehicles with high precision and recall and makes decisions with higher accuracy compared to the state-of-the-art.

Summary In this paper, we explore the problem of providing selective read/write access to the outsourced data for clients using mobile devices in an environment that supports users from multiple domains and where attributes are generated by multiple authorities. We consider Ciphertext‐Policy Attribute‐based Encryption (CP‐ABE) scheme as it can provide access control on encrypted outsourced data. One limitation of CP‐ABE is that the users can modify the access policy specified by the data owner if write operations are introduced in the scheme. We propose a protocol for providing different levels of access to outsourced data that permits the authorized users to perform write operation without altering the access policy specified by the data owner. Our scheme provides fine‐grained read/write access to the users, accompanied with a light weight signature scheme and computationally inexpensive user revocation mechanism suitable for resource‐constrained mobile devices. We provide a theoretical analysis of the security of the proposed protocol and the experimental results measured from a real‐world testbed.

Outsourcing data to the cloud for computation and storage has been on the rise in recent years. In this paper we investigate the problem of supporting write operation on the outsourced data for clients using mobile devices. We consider the Ciphertext-Policy Attribute-based Encryption (CP-ABE) scheme as it is well suited to support access control in outsourced cloud environments. One shortcoming of CP-ABE is that users can modify the access policy specified by the data owner if write operations are incorporated in the scheme. We propose a protocol for collaborative processing of outsourced data that enables the authorized users to perform write operation without being able to alter the access policy specified by the data owner. Our scheme is accompanied with a light weight signature scheme and simple, inexpensive user revocation mechanism to make it suitable for processing on resource-constrained mobile devices. The implementation and detailed performance analysis of the scheme indicate the suitability of the proposed scheme for real mobile applications. Moreover, the security analysis demonstrates that the security properties of the system are not compromised.

Nowadays cloud services have become a cost-effective platform for sharing data and performing large scale computations. As outsourcing data to a third party involves security and privacy concerns, data should be sent to the cloud in encrypted form. To handle access control on encrypted cloud data, Ciphertext-Policy Attribute-based Encryption (CP-ABE) has become very popular. In this scheme data can be encrypted once and can be read multiple times by the authorized users. However, CP-ABE currently has no mechanism to protect against a user of data being able to alter the access policy originally specified by the owner of the data when s/he re-encrypts the modified data (write operation). In this work, we propose a scheme that extends CP-ABE without compromising the security to preserve data owner defined access policy when multiple write operations are performed along with a user revocation mechanism in a setting where multiple authorities generate decryption keys.

Attribute-based encryption schemes provide read access to data based on users' attributes. In these schemes, user privacy is compromised as the access policies are visible. This privacy issue has been addressed in literature by enabling the data owner to obfuscate the policy in a setting where a single authority generates decryption keys. However, a single authority can figure out the hidden access policy which violates user privacy. We present PPDAS, a scheme which overcomes these limitations and makes two contributions. Firstly, we present a mechanism which supports fine-grained read and write operations in a setting where decryption keys are generated by multiple attribute authorities, and the access policy is hidden from all unauthorized entities including the attribute authorities. Our scheme is also accompanied with a user revocation mechanism. Secondly, we show that it is possible to adapt the scheme for accessing data through resource-constrained devices such as smart watches and IoT devices through extensive experimental evaluations.

Outsourcing data to the cloud for computation and storage has been on rise in recent years. In this paper we investigate the problem of supporting write operation on the outsourced data for clients using mobile devices. We consider the Attribute-based Encryption (ABE) scheme as it is well suited to support access control in outsourced cloud environment. Currently there is a gap in the literature on providing write access on the data encrypted with ABE. Moreover, since ABE is computationally expensive, it imposes processing burden on resource constrained mobile devices. Our work has two fold advantages. Firstly, we extend the single authority Ciphertext-Policy Attribute-based Encryption (CP-ABE) scheme to support write operations. Secondly, in achieving this goal, we move some of the expensive computations to a manager and remote cloud server by exploiting their high-end computational power. Our security analysis demonstrates that the security properties of system are not compromised.

We study the problem of finding a minimum energy broadcast tree in duty cycled wireless sensor networks. In such networks, every node has a wakeup schedule and is awake and ready to receive packets or transmit in certain time slots during the schedule and asleep during the rest of the schedule. We assume that a forwarding node needs to stay awake to forward a packet to the next hop neighbor until the neighbor is awake. The minimum energy broadcast tree minimizes the number of additional time units that nodes have to stay awake in order to accomplish broadcast. We show that finding the minimum energy broadcast tree is NP-hard. We give two heuristic algorithms for finding energy-efficient broadcast trees in such networks. We performed extensive simulations to study the performance of these algorithms and compare them with previously proposed algorithms. Our results show that our algorithms exhibit the best performance in terms of average number of additional time units a node needs to be awake, as well as in terms of the number of highly loaded nodes, while being competitive with previous algorithms in terms of total number of transmissions and delay.