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Today, mobile devices such as PDAs and notebooks etc are became most important in human life. A MANET is a mobile ad-hoc network which supports all types of communication such as unicast, multicast and "many-to-many" transmission. Until recently, efficient methods were not devised to generate group key for such groups. Generally, communication in wireless networks is, the risk of sensitive information being intercepted by unintended recipients is a real concern. So, MANETs require efficient and secure group communication. With the model, the groups are established as the forming of group keys. Our results show that this approach can completely satisfy the today's needs of both security and efficiency for group communication. [ABSTRACT FROM AUTHOR]

Vehicular Ad Hoc Network (VANET), a wireless network for V2X communication, provides a new opportunity to create a safer, comfortable and efficient traffic environment. However, the large scale and open environment of VANET brings many problems and challenges to information security, especially the vehicular authentication problem. Many existing authentication schemes always used complex cryptographic algorithms in the process of vehicular authentication to avoid the leak of users' privacy information. Nevertheless, these schemes are unsuitable for VANET due to its higher computational overhead, because VANET's environments are characterized by short communication time between the vehicles and the Road-Side Units (RSUs). Therefore, efficiency and security should be fully considered during the process of vehicular authentication. This paper proposed A Self-checking Authentication Scheme with Higher Efficiency and Security for VANET, named SAES. The proposed scheme adopts self-checking authentication based on pseudonym instead of traditional authentication with the Trusted Authority (TA) participating in the authentication process to minimize the authentication cost. Meanwhile, the group signature is used to reduce the frequency of authentication for legitimate vehicles. The security and performance results of the proposed scheme, analyzed by the provable security and simulation, indicate that this scheme not only meets the requirements of security for VANET but also has a better performance in comparison with existing schemes. [ABSTRACT FROM AUTHOR]

Message authentication and conditional privacy preservation are two critical security issues in vehicular ad hoc networks (VANETs), which have been extensively studied in recent years. To achieve these security issues, many information security technologies have been proposed so far. Among them, pseudonyms-based and group-based messages signing and verifying are two of the main methods adopted in recently published literature. However, analysis points out that both of the two technologies have their downsides. To address these issues, a secure and efficient message authentication protocol (SEMA) is proposed in this article, which aims to achieve mutual authentication among vehicles and road-side units (RSUs) in VANETs by combining the advantages of pseudonyms-based and group-based methods. Security analysis shows that SEMA is robust to various security attacks. Performance evaluation demonstrates that SEMA is computationally lightweight on both vehicles and RSUs. Finally, simulations are performed to prove the feasibility in highway and urban environment. [ABSTRACT FROM AUTHOR]

Vehicle sensor networks (VSN) play an increasingly important part in smart city, due to the interconnectivity of the infrastructure. However similar to other wireless communications, vehicle sensor networks are susceptible to a broad range of attacks. In addition to ensuring security for both data-at-rest and data-in-transit, it is essential to preserve the privacy of data and users in vehicle sensor networks. Many existing authentication schemes for vehicle sensor networks are generally not designed to also preserve the privacy between the user and service provider (e.g., mining user data to provide personalized services without infringing on user privacy). Controllable linkability can be used to facilitate an involved entity with the right linking key to determine whether two messages were generated by the same sender, while preserving the anonymity of the signer. Such a functionality is very useful to provide personalized services. Thus, in this paper, a threshold authentication scheme with anonymity and controllable linkability for vehicle sensor networks is constructed, and its security is analyzed under the random oracle model. [ABSTRACT FROM AUTHOR]

Announcement protocol in Internet of Vehicles (IoV) is an intelligent application to enhance public safety, alleviate traffic jams and improve transportation quality. It requires communication between vehicles, roadside units and pedestrian to disseminate safety-related messages. However, as vehicles connected to internet, it makes them accessible globally to a potential adversary. Safety-related application requires a message to be reliable, however it may intrude the privacy of a vehicle. Contrarily, if some misbehaviour emerges, the malicious vehicles must be able to traceable and revoke from the network. This is a contradiction between privacy and accountability since the privacy of a user should be preserved. For a secure communication among intelligent entities, we propose a novel announcement protocol in IoV using group signature. To the best of our knowledge, our work is the first comprehensive construction of an announcement protocol in IoV that deploys group signature. We show that our protocol efficiently solves these conflicting security requirements of message reliability, privacy and accountability using 5G communication channel. The performance analysis and simulation results signify our work achieves performance efficiency in IoV communication. [ABSTRACT FROM AUTHOR]

Nowadays traveling is the activity that everyone likes the most, but sometimes there is one traveling member who is lost and confused looking for the location of the other members. When traveling, they must bring a smartphone because of its small size and easy to carry anywhere. For this reason, an Android-based smartphone application that is able to send GPS data to all travelling members is proposed. In order to secure data transmission, cryptography and group signature to ensure that only traveling members could find out the location are applied. We use hybrid cryptography, which is a combination of symmetric cryptography using AES and asymmetric cryptography using IB-mRSA. We also add group signature as verification that members are in the same traveling group. The test result showed that the proposed method is safer than the comparison method because the symmetric key is encrypted before the key is distributed, so the attacker can not know the key. The total processing time needed to send data until member get data is 2.01 s.

Mobile sensing receives lots of attention since it exploits sensors embedded in smartphones to gather information for quality improvement of daily life. In particular, mobile users (MUs) carrying smartphones act as queriers who request information provided by MUs who act as data collectors, and the data collection and delivery are facilitated by human mobility and ubiquity. However, additional privacy considerations rise in this paradigm, where MUs might not want to reveal their identities when providing some information at a specific position during a particular period. By adopting group signature, where any member of its group can sign a message on behalf of the entire group, the signer of the sensed information cannot be recognized, and thus, anonymity is preserved. The concept of group signature can be realized when introducing mobile edge computing, where base stations are clustered into a region to serve a group of MUs. In such region-based group signature, MUs located in the same region are grouped and thus are indistinguishable. Due to the localized movement feature of human, MUs might not frequently leave the current group and join a new group, which subsequently reduces the infamous rekeying overhead. We implement group signature on Android smartphones and conduct simulation experiments to investigate the performance of the proposed region-based grouping approach from the perspectives of rekeying overhead and delay. The simulation results show that the region-based grouping method is efficient. Moreover, the optimal group number for the minimization of rekeying overhead is suggested.

Vehicular Ad hoc Network is an emerging area as a key component of the intelligent transport system. Despite the immense researches going on in this area, it is yet to be deployed at its full scale due to lack of trust, safety, and confidentiality in the network. Moreover, the security algorithms proposed till now are complex, and calculations involved are difficult to be completed within the strict real-time constraints. This paper introduces the SignReCrypting Proxy Re-signature scheme, which reduces the time taken for encryption at sender side as well as for decryption at receiver side. Signcryption reduces the computation cost by converting two steps of signature and encryption into one, whereas re-encryption and re-signature enable Alice to decrypt and sign a message on behalf of Bob. These three terminologies altogether with group signature make the proposed algorithm robust, secure, and efficient. The compromised vehicle is revoked from group using dynamic accumulators, and security is verified using automated validation of Internet security protocols and applications.

In the group signature,a member can sign the message instead of the group. The verifier can verify the group signature, meanwhile it will not know the identity of the signer. This paper proposed a forward security group signature scheme based on the Chinese remainder theorem. The proposed scheme would dynamically add and delete the group members without modifying the group public key. The scheme had forward security probability, because the attackers couldn' t achieve the keys in other periods even if they corrupted the keys in a certain period. M eanwhile, the proposed scheme achieves these security properties, including anonymity, revocability, anti-forgery, and traceability. [ABSTRACT FROM AUTHOR]

In this study, anonymity related to the cryptographic scheme is specified, especially the design of anonymous schemes limited to blockchain caused by the implementation of group signatures. In general, the output of this research is the implementation of group signature scheme based on elliptic curve cryptography on blockchain Ethereum. The resulting software aims to address money laundering using cryptocurrency particularly Ethereum. [ABSTRACT FROM AUTHOR]

Recently, oblivious random access machine (ORAM) has been widely used to prevent privacy leakage from user's access pattern. However, in multi-user scenarios, the obliviousness property of ORAM facilitates the malicious data modification by unauthorized users, which brings a new security challenge of user accountability to ORAM applications. Moreover, based on our observations, existing user accountability schemes for multi-user ORAM induce the extremely unacceptable overhead in both time and storage. What is worse, it is still inherent the traditional cloud accountability problem that the untrusted cloud server may have misbehavior on storing the outsourced data. In this paper, we focus on the issue that how to do accountability for both malicious users and untrusted cloud server without the independent trusted third party server. To address the above problem, we design and implement a Traceable Oblivious RAM, or T-ORAM for short, a cryptographic system that protects the privacy of users and the integrity of outsourced data based on group signatures. It can detect malicious users quickly by utilizing the traceability property of group signatures, and cost less storage overhead comparing with the existing solutions. Then, we further propose a more secure solution of Blockchain-based Traceable Oblivious RAM (BT-ORAM). Specifically, by introducing the blockchain technology, BT-ORAM can detect the malicious behavior from both malicious users and untrusted cloud server. BT-ORAM is the first accountability work for multi-user ORAM that deal with both malicious users and the untrusted cloud server. Finally, security analysis and experimental results show that our method outperforms the state-of-the-art accountability work for oblivious RAM, S-GORAM, in both security and performance. • We summarize the two critical problems in data integrity protection by applying ORAM technology into the cloud storage. • We present a Traceable Oblivious RAM (T-ORAM) with malicious user accountability for multi-user ORAM. • To achieve a high-level secure ORAM system, we further propose a Blockchain-based Traceable Oblivious RAM (BT-ORAM) with a comprehensive accountability scheme. • Experimental results show that T-ORAM has a better performance than existing related solutions, and BT-ORAM can achieve a higher level security than previous work. [ABSTRACT FROM AUTHOR]

Quantum group signature is an important branch of quantum signature. Most of the existing quantum group signature schemes require that all the signatories must be present to generate a valid signature, and this property may limit their application in practice. In this paper, we will propose a quantum (t, n) threshold group signature scheme. In our scheme, n signatories compose a group, and any t out of these n signatories can generate a valid signature on behalf of the group. The t signatories use the quantum-controlled-not operations to expand the quantum message into t-particle entangled states, and then use the entanglement swapping to transmit the quantum message to the receiver. The receiver performs the single-particle measurements and unitary operations to recover the initial quantum message, and then verifies the signature with the help of the arbitrator. Compared to the existing quantum group signature schemes, our (t, n) threshold scheme will be more flexible in practice. [ABSTRACT FROM AUTHOR]

Vehicular ad hoc networks (VANETs) enable wireless communication between vehicles and roadside infrastructure to provide a safer and more efficient driving environment. However, due to VANETs wireless nature, vehicles are exposed to several security attacks when they join the network. In order to protect VANETs against misbehaviours, one of the vital security requirements is to revoke the misbehaved vehicles from the network. Some existing revocation protocols have been proposed to enhance security in VANETs. However, most of the protocols do not efficiently address revocation issues associated with group signature-based schemes. In this paper, we address the problem by constructing a revocation protocol particularly for group signatures in VANETs. We show that this protocol can be securely and efficiently solve the issue of revocation in group signature schemes. The theoretical analysis and simulation results demonstrate our work is secure against adversaries and achieves performance efficiency and scalability. [ABSTRACT FROM AUTHOR]

Vehicular ad hoc networks (VANET) is one of the most awaited and ambitious projects of Intelligent Transport System (ITS), where vehicles are permitted to talk with each other. The ultimate goal of the network is to develop a connected network of automobiles, and eventually to reduce traffic and accidents. However, VANET is an ad hoc network without any infrastructure. Apart from architectural issues, there are plenty of security and performance issues, which makes it difficult to be implemented. Therefore, we are using fully authenticated Signcryption technique along with re-cryptography and shareable cloud to make the network safe, reliable and robust. Signcryption combines signature and encryption in a single step, hence decreasing the number of computations. Re-cryptography allows alternative authorities to take charge of the primary authority while maintaining communication transparency. Group signature facilitates secure communication within the group. Security has been verified using Burrows-Abadi-Needham (BAN) logic and Automated Validation of Internet Security Protocols and Applications (AVISPA). [ABSTRACT FROM AUTHOR]

Blockchain technology has attracted significant attention since its publication. However, most existing blockchain platforms are isolated systems, which makes it difficult to exchange data among different blockchains. The industry has proposed the notary schemes to enhance blockchain interoperability, which can exchange messages among different blockchains through a notary. However, conventional notary schemes are centralized, which suffers from single point of failures. To address these issues, this paper proposes a distributed cross-chain notary model with regulatory mechanisms, based on improved threshold group signatures. We improve the group signature scheme by setting up a group of tracing authorities to achieve distributed tracing. Furthermore, we incorporate this signature scheme into our notary scheme, where a group of notaries signs cross-chain transactions using group signatures. We also introduce a group of regulators to reveal the true identities of malicious notaries when disputes occur. Finally, we prove the security of our signature scheme based on the Random Oracle Model. In our experiments, when the number of notaries is 102 and the threshold is 2/3 of that, it takes 166 ms to set up and generate signature. Also, it takes 161 ms for regulators to reveal the true identities of malicious notaries. [ABSTRACT FROM AUTHOR]

Recently, with the great development of e-health, more and more countries have made certain achievements in the field of electronic medical treatment. The digitization of medical equipment and the structuralization of electronic medical records are the general trends. While bringing convenience to people, the explosive growth of medical data will further promote the value of mining medical data. Obviously, finding out how to safely store such a large amount of data is a problem that urgently needs to be solved. Additionally, the particularity of medical data makes it necessarily subject to great privacy protection needs. This reinforces the importance of designing a safe solution to ensure data privacy. Many existing schemes are based on single-server architecture, which have some natural defects (such as single-point faults). Although blockchain can help solve such problems, there are still some deficiencies in privacy protection. To solve these problems, this paper designs a medical data privacy protection system, which integrates blockchain, group signature, and asymmetric encryption to realize reliable medical data sharing between medical institutions and protect the data privacy of patients. This paper proves theoretically that it meets our security and privacy requirements, and proves its practicability through system implementation.

In cloud environments, group data sharing has become a hot topic in recent years. How to share data securely and efficiently in cloud environments is an urgent problem to be solved. Recently, an anonymous and traceable group data sharing scheme was proposed by Shen et al. to address this issue. They constructed their scheme using a group signature scheme as the building block. In this comment, we discuss the security of their group signature scheme and point out that it does not achieve the anonymity which they claimed and give a corresponding attack. [ABSTRACT FROM AUTHOR]

Starting with the presented concept by Chaum and van Heijst and its refers to digitally signing for a document by a group member, such signatures allows the signers to remains anonymous but any verifier can confirm that the signer is a group member. The signatory anonymity can be revealed only by a designated group authority that has some auxiliary information. We present a complexity efficient group signature scheme based on zero knowledge and Schnorr signature algorithm. The scheme has two phases: the first one demonstrates that the signer is a member of the group while the second generates the message signature. In the end, we modify the classic scheme using differential elliptic curve cryptography to increase the system's performance against differential attacks.

Pervasive social networking (PSN) supports instant social activities anywhere and at any time with the support of heterogeneous networks, where privacy preservation is a crucial issue. One of the effective methods to achieve privacy preservation is anonymous authentication on trust. However, few literatures pay attention to it. In this paper, we propose an anonymous authentication scheme based on group signature for authenticating trust levels rather than identities of nodes in order to avoid privacy leakage and guarantee secure communications in PSN. The scheme achieves secure anonymous authentication with anonymity and conditional traceability with the support of a trusted authority (TA). We also provide a mechanism to guarantee communications among nodes when TA is not available for some nodes. In addition, the utilization of batch signature verification further improves the efficiency of authenticity verification on a large number of messages. Performance analysis and evaluation further prove that the proposed scheme is effective with regard to privacy preservation, computation complexity, communication cost, flexibility, reliability, and scalability.

Mobile Ad hoc Network is stated as a cluster that contains Digital data terminals and they are furnished with the wireless transceivers which are able to communicate with each other with no need of any fixed architecture or concentrated authority. Security is one of the major issues in MANETs because of vast applications such as Military Battlefields, emergency and rescue operations[10]. In order to provide anonymous communications and to identify the malicious nodes in MANETs, many authors have proposed different secure routing protocols but each protocol have their own advantages and disadvantages. In MANTE’s each and every node in the communicating network functions like router and transmits the packets among the networking nodes for the purpose of communication[11]. Sometimes nodes may be attacked by the malicious nodes or the legitimate node will be caught by foemen there by controlling and preventing the nodes to perform the assigned task or nodes may be corrupted due to loss of energy. So, due to these drawbacks securing the network under the presence of adversaries is an important thing. The existing protocols were designed with keeping anonymity and the identification of vicious nodes in the network as the main goal. For providing better security, the anonymity factors such as Unidentifiability and Unlinkability must be fully satisfied[1]. Many anonymous routing schemes that concentrate on achieving anonymity are proposed in the past decade and they provides the security at different levels and also provides the privacy protection that is of different cost. In this paper we consider a protocol called Authenticated Secure Routing Protocol proposed which provides both security & anonymity. Anonymity is achieved in this protocol using Group signature. Over all by using this protocol performance in terms of throughput as well as the packet dropping rate is good compared to the other living protocols.

Vehicular ad hoc networks (VANETs) face two important and conflicting challenges with regards to security: preserve the privacy of vehicles in order to prevent malicious entities from tracking users and detect and remove bad actors that attempt to game the system for their own advantage. In particular, detecting Sybil attacks, in which one node attempts to appear as many, seemingly conflicts with the goal of privacy preservation, and existing schemes fail on either one or both accounts. To fill this gap, we present a hierarchical key management system which uses short group signatures to preserve member privacy at lower levels while allowing mid-level nodes to detect Sybil attacks and highly trusted nodes at the top of the hierarchy to completely reveal the real identities of malicious nodes in order to prevent them from rejoining the system and for use by legal authorities. In addition, we present an argument for relaxing the requirement of backward secrecy in VANET groups in the case when no malicious activity has been detected.

The vehicular ad hoc networks (VANETs) face serious privacy threats, due to the numerous vehicles, variable node speeds and network openness. To tackle the threats, this paper proposes a conditional privacy protection (CPP) mechanism based on group signature anonymous authentication and the cryptographic algorithms of bilinear pairings on elliptic curve. Unlike most existing group signature mechanisms, this mechanism can achieve anonymous and nonconnectable conditions at the same time, and allow the trust authority (TA) to track the identity of the sender of any controversial message. Finally, simulation results show that the CPP outperformed the group signature-based (GSB) protocol and the human anonymous keysbased (HAB) protocol in verification speed, tacking efficiency and scalability. [ABSTRACT FROM AUTHOR]

In order to address the anonymous batch authentication problem of a legal reader to many tags in RFID (Radio Frequency Identification) system, an efficient RFID anonymous batch authentication protocol was proposed based on group signature. The anonymous batch authentications of reader to many tags are achieved by using a one-time group signature based on Hash function; the authentication of the tag to the reader is realized by employing MAC (Message Authentication Code). The tag's anonymity is achieved via the dynamic TID (Temporary Identity) instead of the tag's identity. The proposed protocol can resist replay attacks by using random number. Theoretical analyses show that, the proposed protocol reaches the expected security goals. Compared with the protocol proposed by Liu, the proposed protocol reduces the computation and storage of the server and tag while improving the security. [ABSTRACT FROM AUTHOR]

Anonymous authentication is one of the most critical tools for the privacy protection in Internet-of-Things (IoT). The primitive of group signature has been widely applied to achieving anonymous authentication. Any mobile device is able to prove its privilege of the access control to a remote server which is an authenticated device with valid attestation. However, the traditional group signature schemes cannot support dynamic authentication efficiently. Furthermore, they are insecure against quantum attack. To tackle the abovementioned challenges, a new lattice-based dynamic group signature scheme is proposed. The new scheme allows any user to dynamically join the group while achieving efficient revocation. Furthermore, it is shown that the new scheme can achieve the security of non-frameability. The security of non-frameability guarantees that any user's signature can not be forged by other users in the system. In addition, the scheme based on the hardness of lattice problem in the random oracle model is provably secure. The efficiency analysis demonstrates that the scheme is effective in practice. [ABSTRACT FROM AUTHOR]

In the cloud computing, different cloud service providers are often in different trust domains. As the traditional identity authentication mode cannot be applied to the cloud computing, the cross-domain identity authentication mechanism is needed to solve the identity authentication problem in the cloud computing. In view of the security problems in cloud computing, a cross-domain identity authentication scheme based on group signature is proposed. This scheme introduces a group of cloud service providers and users who are located in different trust domains. Any member of the group can generate the signature on behalf of the whole group, making the user access the cloud service provider in the case of privacy security. At the same time, with traceability it can track illegal operation of illegal users. In addition, the scheme uses the Chinese Remainder Theorem to integrate the message, and it can control the length of the data in the calculation process, simplifying the calculation process. It also realizes the join and revocation of group members without changing the key of other legitimate group members, and the maintenance cost of authentication schemes is low. The results show that the scheme has the advantages of anonymity, anti-counterfeit, traceability, anti- joint attack and so on. It can not only realize tracking function under the condition of guaranteeing user's privacy, but can also simplify the authentication calculation process to improve the efficiency of the cross domain identity authentication, and its performance is more suitable for large-scale cloud computing environment. [ABSTRACT FROM AUTHOR]

This paper deals with an anonymous data collection in the Internet of Things (IoT). the privacy and anonymity of the data source is important for many IoT applications, such as in agriculture, health, and automotive. the proposed data‑collection system provides anonymity for the data sources by applying a cooperation group scheme. the group scheme also provides a low power consumption. the system is built upon the Tor (The Onion Router) anonymous network, which is a part of the Internet darknet. the proposed system was designed for the Android devices on the client side and for Java environment on the server side. We evaluated the anonymous data collection in a real‑use scenario that covers selected data acquisition (e.g. signal strength) from smartphones triggered by their geographical location change. the results show that the proposed system provides the sufficient data source anonymity, an effective revocation, a low computational cost and a low overhead.

In modern applications, such as Electronic Voting, e-Health, e-Cash, there is a need that the validity of a signature should be verified by only one responsible person. This is opposite to the traditional digital signature scheme where anybody can verify a signature. There have been several solutions for this problem, the first one is we combine a signature scheme with an encryption scheme; the second one is to use the group signature; and the last one is to use the strong designated verifier signature scheme with the undeniable property. In this paper, we extend the traditional digital signature scheme to propose a new solution for the aforementioned problem. Our extension is in the sense that only a designated verifier (responsible person) can verify a signer’s signature, and if necessary (in case the signer refuses to admit his/her signature) the designated verifier without revealing his/her secret key is able to prove to anybody that the signer has actually generated the signature. The comparison between our proposed solution and the three existing solutions shows that our proposed solution is the best one in terms of both security and efficiency.