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Anonymous identity-based encryption (AIBE) is an extension of identity-based encryption (IBE) that enhances the privacy of a ciphertext by providing ciphertext anonymity. In this paper, we introduce the concept of revocable IBE with anonymous revocation (RIBE-AR), which can issue an update key and hide the revoked set of the update key that efficiently revokes private keys of AIBE. We first define the security models of RIBE-AR and propose an efficient RIBE-AR scheme in bilinear groups. Our RIBE-AR scheme is similar to the existing RIBE scheme in terms of efficiency, but it is the first RIBE scheme to provide additional ciphertext anonymity and revocation privacy. We show that our RIBE-AR scheme provides selective message privacy, selective identity privacy, and selective revocation privacy.

Recently, using advanced cryptographic techniques to process, store, and share data securely in an untrusted cloud environment has drawn widespread attention from academic researchers. In particular, Ciphertext-Policy Attribute-Based Encryption (CP-ABE) is a promising, advanced type of encryption technique that resolves an open challenge to regulate fine-grained access control of sensitive data according to attributes, particularly for Internet of Things (IoT) applications. However, although this technique provides several critical functions such as data confidentiality and expressiveness, it faces some hurdles including revocation issues and lack of managing a wide range of attributes. These two issues have been highlighted by many existing studies due to their complexity which is hard to address without high computational cost affecting the resource-limited IoT devices. In this paper, unlike other survey papers, existing single and multiauthority CP-ABE schemes are reviewed with the main focus on their ability to address the revocation issues, the techniques used to manage the revocation, and comparisons among them according to a number of secure cloud storage criteria. Therefore, this is the first review paper analysing the major issues of CP-ABE in the IoT paradigm and explaining the existing approaches to addressing these issues.

With the rapid development of big data and Internet of things (IOT), the number of networking devices and data volume are increasing dramatically. Fog computing, which extends cloud computing to the edge of the network can effectively solve the bottleneck problems of data transmission and data storage. However, security and privacy challenges are also arising in the fog-cloud computing environment. Ciphertext-policy attribute-based encryption (CP-ABE) can be adopted to realize data access control in fog-cloud computing systems. In this paper, we propose a verifiable outsourced multi-authority access control scheme, named VO-MAACS. In our construction, most encryption and decryption computations are outsourced to fog devices and the computation results can be verified by using our verification method. Meanwhile, to address the revocation issue, we design an efficient user and attribute revocation method for it. Finally, analysis and simulation results show that our scheme is both secure and highly efficient.

In vehicular ad-hoc networks (VANETs), the correctness of a message requires authentication of the origin vehicle. In this paper, we introduce a novel authentication scheme for VANETs which suggests a new solution for secure vehicle communications. The proposed scheme is an road side unit (RSU) based scheme in which the master key of the Trusted Authority (TA) is embedded in a tamper-proof device provided at the RSUs. Compared with the schemes that store the master key in the on-board units, our scheme is more practical because of a secure and high speed communication link between TA and RSUs. To the best of our knowledge, this solution has not yet been devised for secure authentication in VANETs and the same objective has been fulfilled in this paper. Moreover, we introduce a formal proof to prove the security of the proposed scheme. Finally, we present a simulation and comparison indicating the performance and efficiency of our scheme.

Despite their strong humanitarian reputations abroad, Norway and Canada have adopted domestic immigration policies that produce permanently precarious residents. These policies affect individuals—including refugees, permanent residents, and naturalized citizens—who have traditionally enjoyed secure legal statuses. Adopting the analytic lens of ‘probationary immigration’, this article explores the legal mechanisms behind three interrelated developments in both countries: 1) the fragmentation of protection regimes in terms of access, rights and duration; 2) stricter/less predictable requirements for permanent residence and citizenship; and 3) intensified practice regarding the revocation of citizenship.

Any system or network is always susceptible to attacks. If an adversary has access to the network, they may disrupt the network in several ways. Sybil attack, selective forwarding, tampering, etc., are some of the attacks that disrupt the network. If the sensor network is employed in critical areas such as warzones or border protection systems, any attack or breach of security may prove to be fatal. Therefore, proper security mechanisms have to be integrated into the system to ensure that the data remains secure. In our project, we intend to identify and isolate the compromised nodes that selectively forwards data packets. The proposed protocol uses a reputation based system to determine the integrity of the neighboring nodes. Once a compromised node has been identified, that node is excluded from further communication after verification from base station.

The rapid advancement of the Internet of Vehicles (IoV) has led to a massive growth in data received from IoV networks. The cloud storage has been a timely service that provides a vast range of data storage for IoV networks. However, existing data storage and access models used to manage and protect data in IoV networks have proven to be insufficient. They are centralized and usually accompanied by a lack of trust, transparency, security, immutability, and provenance. In this paper, we propose VBlock, a blockchain-based system that addresses the issues of illegal modification of outsourced vehicular data for smart city management and improvement. We introduce a novel collusion-resistant model for outsourcing data to cloud storage that ensures the network remains tamper-proof, has good data provenance and auditing, and solves the centralized problems prone to the single point of failure. We introduced a key revocation mechanism to secure the network from malicious nodes. We formally define the system model of VBlock in the setting of a consortium blockchain. Our simulation results and security analysis show that the proposed model provides a strong security guarantee with high efficiency and is practicable in the IoV environment.

Attribute-based encryption can be used to realize fine-grained data sharing in open networks. However, in practical applications, we have to address further challenging issues, such as attribute revocation and data search. How do data users search for the data they need in massive amounts of data? When users leave the system, they lose the right to decrypt the shared data. In this case, how do we ensure that revoked users cannot decrypt shared data? In this paper, we successfully address these issues by proposing a hidden policy attribute-based data sharing scheme with direct revocation and keyword search. In the proposed scheme, the direct revocation of attributes does not need to update the private key of non-revoked users during revocation. In addition, a keyword search is realized in our scheme, and the search time is constant with the increase in attributes. In particular, the policy is hidden in our scheme, and hence, users’ privacy is protected. Our security and performance analyses show that the proposed scheme can tackle the security and efficiency concerns in cloud computing.

This article not only considers conversions to Lutheranism from the convert’s perspective, but understands conversion as a process involving multiple actors with a range of motivations. This perspective moves the conversation away from the converts’ own narratives and instead concentrates on Lutheran theologians, urban dignitaries and Protestant princes, who participated in the conversions in various ways. It asks how these actors benefitted from supporting the converts and argues that they actively promoted conversion to Lutheranism. Conversion became a key feature of the Lutheran self-perception and theologians and princes celebrated and promoted them in Germany and beyond. Contrary to previous scholarship, this article shows that Lutherans actively advocated conversions and the converts played a crucial role in the construction of a Lutheran identity.