Group Signature

A vehicular ad hoc network is a capable method of making possible road well-being, traffic supervision, as well as information distribution for driving users and travelers. One definitive objective in the blueprint of this type of network is to refuse to accept a variety of malevolent mistreatment and security assaults. The paper analyzed the existing procedure, which has covered the ways of offering security duties and conserving user solitude in the context of wireless access in vehicular environments (WAVE) applications. To make the standards more realistic, it considers techniques of certificate revocation and conditional privacy preservation. These techniques are found to be the most promising ones in vehicular ad hoc networks (VANET). Therefore, a group of narrative security methods is proposed for the safe implementation of the techniques of certificate revocation and conditional privacy preservation. For enhancement of security, the paper proposes that the message should be encapsulated with a proper certificate and be duly signed. For faster communication, we propose the use of optical wireless communication (OWC) between an onboard unit (OBU) and a roadside unit (RSU).

A Zero-knowledge protocol provides provably secure entity authentication based on a hard computational problem. Among many schemes proposed since 1984, the most practical rely on factoring and discrete log, but still they are practical schemes based on NP-hard problems. Among them, the problem SD of decoding linear codes is in spite of some 30 years of research effort, still exponential. We study a more general problem called MinRank that generalizes SD and contains also other well known hard problems. MinRank is also used in cryptanalysis of several public key cryptosystems such as birational schemes (Crypto'93), HFE (Crypto'99), GPT cryptosystem (Eurocrypt'91), TTM (Asiacrypt'2000) and Chen's authentication scheme (1996). We propose a new Zero-knowledge scheme based on MinRank. We prove it to be Zero-knowledge by black-box simulation. An adversary able to fraud for a given MinRank instance is either able to solve it, or is able to compute a collision on a given hash function. MinRank is one of the most efficient schemes based on NP-complete problems. It can be used to prove in Zero-knowledge a solution to any problem described by multivariate equations. We also present a version with a public key shared by a few users, that allows anonymous group signatures (a.k.a. ring signatures).

Acoustic territorial displays are common among birds but comparatively rare among mammals. An exceptionally vocal mammal well-known for its elaborate territorial displays is the polygynous greater sac-winged bat, Saccopteryx bilineata. Male S. bilineata are often philopatric and establish small territories in their birth colony in which females can roost during the day. During territorial defense, males produce complex territorial songs that are learned through vocal imitation. Territorial songs are mainly produced at dawn and dusk. We studied social influences on male vocal activity and the occurrence of vocal signatures in territorial songs of 27 male S. bilineata from 12 differentsized colonies in Panama. Males produced significantly more territorial songs when they had more territorial neighbors or when they had females roosting in their territories, indicating that male vocal activity rises with increasing male-male competition. Territorial songs are multisyllabic vocalizations with low-frequency buzz syllables being most prominent. We found statistical evidence for a pronounced individual signature encoded in the buzz syllables of territorial songs that could facilitate individual recognition among rival neighbors. Additionally, we found a vocal group signature in territorial songs, suggesting that young males may learn territorial songs from more than one tutor male. Resident male S. bilineata appear to cooperatively defend their colony against male intruders, making a group signature in territorial songs potentially advantageous.

In this paper, we introduce Attribute-Based Signatures with User-Controlled Linkability (ABS-UCL). Attribute-based signatures allow a signer who has enough credentials/attributes to anonymously sign a message w.r.t. some public policy revealing neither the attributes used nor his identity. User-controlled linkability is a new feature which allows a user to make some of his signatures directed at the same recipient linkable while still retaining anonymity. Such a feature is useful for many reallife applications. We give a general framework for constructing ABS-UCL and present an efficient instantiation of the construction that supports multiple attribute authorities.

This paper proposes a new efficient signature scheme from bilinear maps that is secure in the standard model (i.e., without the random oracle model). Our signature scheme is more effective in many applications (e.g., blind signatures, group signatures, anonymous credentials etc.) than the existing secure signature schemes in the standard model such as the Boneh-Boyen [6], Camenisch-Lysyanskaya [10], Cramer-Shoup [15] and Waters [33] schemes (and their variants). The security proof of our scheme requires a slightly stronger assumption, the 2SDH assumption, than the SDH assumption used by Boneh-Boyen. As typical applications of our signature scheme, this paper presents efficient blind signatures and partially blind signatures that are secure in the standard model. Here, partially blind signatures are a generalization of blind signatures (i.e., blind signatures are a special case of partially blind signatures) and have many applications including electronic cash and voting. Our blind signature scheme is much more efficient than the existing secure blind signature schemes in the standard model such as the Camenisch-Koprowski-Warinsch [8] and Juels-Luby-Ostrovsky [22] schemes, and is also almost as efficient as the most efficient blind signature schemes whose security has been analyzed heuristically or in the random oracle model. Our partially blind signature scheme is the first one that is secure in the standard model and it is very efficient (almost as efficient as our blind signatures). We also present a blind signature scheme based on the Waters signature scheme.

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Vehicular adhoc network is one of the recent area of research to administer safety to human lives, controlling of messages and in disposal of messages to users and passengers. VANETs allows communication of moving vehicular nodes. Movement of nodes leads in changing network size and scenario. Whenever a new node joins the network, there is a threat of malicious node attack. So, we need an environment that is secure and trust worthy. Therefore a new cluster based secure technique is proposed where cluster head is responsible for providing communication between the vehicular nodes. Performance parameters used in this paper are message drop ratio, packet delay ratio and verification time.

We propose a version of ring signatures for which the set of potential signers may be reduced: the real signer can prove that he or she has created the signature, while every other member of the ring can prove not to be the signer. Possibility to run these protocols is triggered by publishing certain secret information. The proposed scheme is an intermediate solution between the classical ring and group signatures, and can be used for instance for e-auction schemes.

Vehicular Ad Hoc Networks (VANETs) are a particular subclass of mobile ad hoc networks that raise a number of security challenges, notably from the way users authenticate the network. Authentication technologies based on existing security policies and access control rules in such networks assume full trust on Roadside Unit (RSU) and authentication servers. The disclosure of authentication parameters enables user's traceability over the network. VANETs' trusted entities (e.g. RSU) can utilize such information to track a user traveling behavior, violating user privacy and anonymity. In this paper, we proposed a novel, lightweight, Adaptive Group-based Zero Knowledge Proof-Authentication Protocol (AGZKP-AP) for VANETs. The proposed authentication protocol is capable of offering various levels of users' privacy settings based on the type of services available on such networks. Our scheme is based on the Zero-Knowledge-Proof (ZKP) crypto approach with the support of trade-off options. Users have the option to make critical decisions on the level of privacy and the amount of resources usage they prefer such as short system response time versus the number of private information disclosures. Furthermore, AGZKP-AP is incorporated with a distributed privilege control and revoking mechanism that render user's private information to law enforcement in case of a traffic violation.

Vocal learning is well known among passerine and psittacine birds, but most data on mammals are equivocal. Speci¢c bene¢ts of vocal learning are poorly understood for most species. One case where vocal learning should be favoured by selection is where calls indicate group membership and group mates are unrelated. Female greater spear-nosed bats, Phyllostomus hastatus, live in stable groups of unrelated bats and use loud, broadband calls to coordinate foraging movements of social group mates. Bats bene¢t from group foraging. Calls di¡er between female social groups and cave colonies, and playback experiments demonstrate that bats perceive these acoustic di¡erences. Here I show that the group distinctive structure of calls arises through vocal learning. Females change call structure when group composition changes, resulting in increased similarity among new social group mates. Comparisons of transfers with agematched half-sibs indicate that call changes are not simply due to maturation, the physical environment or heredity. These results suggest that studies testing vocal learning in mammals could pro¢t by focusing on vocalizations that signify group membership.

The advent of the cloud computing makes storage outsourcing becomes a rising trend, which promotes the secure remote data auditing a hot topic that appeared in the research literature. Recently some researches consider the problem of secure and efficient public data integrity auditing for shared dynamic data. In this paper, signifies that the collusion attack in the exiting scheme and provide an efficient public integrity auditing scheme with secure group user revocation based on vector commitment and verifier-local revocation group signature. Analysis shows a concrete scheme based on the scheme definition. The scheme supports the public checking and efficient user revocation and also some nice properties, such as confidently, efficiency, count ability and traceability of secure group user revocation.

Without trust, buyers may not join a coalition. Despite the tremendous need for trustworthy relationships in buyer coalitions, no current buyer coalition scheme explicitly tackles confidence issues with blockchain technology. This study proposes an algorithmic design, the blockchain-based trusty buyer coalition scheme, to satisfy the trust requirement among different actors while forming the coalition. All activities forming a coalition through a decentralized public ledger can be explicitly examined. Consequently, the proposed algorithm can ensure anonymity within a community, resulting in trusting relationships. Furthermore, the proposed algorithm can ensure correctness and accountability by recognizing misbehavior and enforcing alternative forms of punishment. Additionally, the discovered algorithm can be applied to mobile commerce applications.

In order to improve road traffic safety, reduce congestion, improving driving experience, intelligent transportation systems and vehicular networking concepts arises at the historic moment. In vehicle larger density scene, can't guarantee safe reliable and information transmission timely, sometimes can also cause problems such as the broadcast storm. Represented by LTE-A evolution of new generation of mobile communication network rapid development. It performance optimization in the system capacity, the peak rate, transmission delay and other key. In this paper, we proposed a privacypreserving and cross-domain group authentication scheme. It can effectively solve the security problems. Theoretical analysis and simulation results are shown that compared with other authentication protocol, our scheme has more security properties and better performance.

A Publicly Verifiable Secret Sharing (PVSS) scheme allows anyone to verify the validity of the shares computed and distributed by a dealer. The idea of PVSS was introduced by Stadler in [18] where he presented a PVSS scheme based on Discrete Logarithm. Later, several PVSS schemes were proposed. In [2], Behnad and Eghlidos present an interesting PVSS scheme with explicit membership and disputation processes. In this paper, we present a new PVSS having the advantage of being simpler while offering the same features. 1

Attribute-Based Encryption (ABE) is an advanced cryptographic technique that secures data by leveraging user attributes rather than conventional cryptographic keys. Expanding upon this, Multi-Authority Attribute-Based Encryption (MA-ABE) introduces multiple governing bodies, each managing distinct sets of attributes, to enhance flexibility and control in large-scale systems. The primary objective of this research is to address the challenges of privacy, anonymity, and access control in Identity and Access Management (IAM) through a novel MA-ABE framework. This study fills a critical gap in the current literature by providing a decentralized solution that effectively distributes authority and integrates advanced cryptographic techniques to safeguard sensitive data against unauthorized access and malicious attacks. The methodology employed integrates Elliptic Curve Cryptography (ECC) and the Elliptic Curve Diffie-Hellman (ECDH) key exchange for secure key generation and sharing. A novel approach for signing data with temporal context is introduced, utilizing Digital Signature Standard (DSS) with timestamping to enhance data integrity and authentication. The proposed model also incorporates Advanced Encryption Standard (AES) in EAX mode to ensure data confidentiality and integrity during encryption and decryption processes. The integration of these algorithms within a decentralized MA-ABE framework represents a significant advancement in the field of cryptographic systems for IAM. The findings demonstrate that the proposed MA-ABE system effectively maintains data security, user privacy, and anonymity. The experimental results show robust performance in handling dynamic access scenarios, enforcing strict access control, and preserving user anonymity without compromising system efficiency.

It is considered a group signature scheme in frame of which different sets of signers sign electronic documents with hidden signatures and the head of the signing group generates a group signature of fixed size. A new mechanism for imbedding the information about signers into a group signature is proposed. The method provides possibilities for reducing the signature size and to construct collective signature protocols for signing groups. New group signature and collective signature protocols based on the computational difficulty of discrete logarithm are proposed.

Anonymity is an important feature in many twoparty communication systems. Its main meaning is that either the message sender or the receiver (or both) is unidentifiable to other users, even between themselves. Many mechanisms have been proposed to hide the identity of the sender, receiver, or both. Similarly, anonymity is an important feature in multiparty computing environments, but, little research has been conducted on this topic even though many secure group communication schemes have been proposed. In this paper, we highlight the concepts of anonymity for secure group communication and propose to extend a recently invented innovative group key management mechanism, Access Control Polynomial [54], to multi-party group communication. This newly extended scheme can not only enforce anonymous group membership and group size but also implement secure and anonymous group communication. The experimental results and comparison with existing schemes show that the new scheme is elegant, flexible, efficient and practical. The paper also summarizes and classifies typical existing anonymous group communication schemes.

This thesis studies a particular functionality for privacy-preserving systems, that allows a user to demonstrate a proof showing that the user has been approved by a number of authorities, without revealing their identities. We first consider this functionality for two fundamental cryptosystems: digital signature schemes, and public key encryption schemes, and introduce a new notion “grade” for these systems. Within this scope, we formalize two new primitives, graded signatures and graded encryption. Graded signature schemes enable a user to consolidate a set of signatures on a message m originating from l different signers. The resulting consolidated signature object on m reveals nothing more than the grade of the signature and the validity of the original signatures without leaking the identity of the signers. On the other hand, graded encryption schemes allow a sender to specify a numerical grade i for the ciphertext during the encryption depending on the importance of the messag...

Linkable ring signatures is a useful cryptographic tool for constructing applications such as ones relative to electronic voting (e-voting), digital cashes (e-cashes) as well as cloud computing. Equipped with linkable ring signatures, e-voting, e-cash systems can simultaneously enjoy the privacy and the unreusability properties thanks to the anonymity and the linkability of linkable ring signatures. Likewise, cloud servers can enjoy a privacy-preserving ability, a flexible access control and an efficient security management with linkable ring signatures. Moreover, linkable ring signatures built in the identity-based setting would help to remove the expense of using the conventional public key infrastructure and also could be applied to the user management. This primitive hence would be suitable for huge-scale applications. In this paper, we present the first identity-based linkable ring signatures (IdLRS) in both integer lattice and ideal lattice setting. The proposed IdLRS is proved secure in the random oracle model and based on the hardness of the short integer solution and ring short integer solution assumption. We also implement the proposed idLRS as a proof of concept and then do some experiments to evaluate the running times and the sizes. INDEX TERMS Identity-based linkable ring signatures, e-voting, e-cash, cloud computing, lattices.

Linkable ring signatures is a useful cryptographic tool for constructing applications such as ones relative to electronic voting (e-voting), digital cashes (e-cashes) as well as cloud computing. Equipped with linkable ring signatures, e-voting, e-cash systems can simultaneously enjoy the privacy and the unreusability properties thanks to the anonymity and the linkability of linkable ring signatures. Likewise, cloud servers can enjoy a privacy-preserving ability, a flexible access control and an efficient security management with linkable ring signatures. Moreover, linkable ring signatures built in the identity-based setting would help to remove the expense of using the conventional public key infrastructure and also could be applied to the user management. This primitive hence would be suitable for huge-scale applications. In this paper, we present the first identity-based linkable ring signatures (IdLRS) in both integer lattice and ideal lattice setting. The proposed IdLRS is proved secure in the random oracle model and based on the hardness of the short integer solution and ring short integer solution assumption. We also implement the proposed idLRS as a proof of concept and then do some experiments to evaluate the running times and the sizes. INDEX TERMS Identity-based linkable ring signatures, e-voting, e-cash, cloud computing, lattices.

For increasing safety of driving, intelligent vehicles in vehicular ad hoc networks (VANETs) communicate with each other by sending announcements. The existence of a system that guarantees the trustworthiness of these announcements seems necessary. The proposed approach generating announcements should be preserved from internal and external attackers that attempt to send fake messages. In this paper, we use a group-based endorsement mechanism based on threshold signatures against internal attackers. We choose NTRUSign as a public key cryptosystem for decreasing signature generation and verification times. This approach optimizes the network overhead and consequently its performance. In this scheme, also the privacy of signers and endorsers that generate or endorse trustworthy announcements is preserved.

Many types of digital signature schemes have been researched and published in recent years. In this paper, we propose two new types of collective signature schemes, namely i) the collective signature for several signing groups and ii) the collective signature for several individual signings and several signing groups. And then we used two difficult problems factoring and discrete logarithm to construct these schemes. To create a combination of these two difficult problems we use the prime module p with a special structure: p = Nn + 1 with n = rq, N is an even number, r and q are prime numbers of at least 512 bit. Schnorr's digital signature scheme and the RSA key generation algorithm are used to construct related basic schemes such as the single signature scheme, the collective signature scheme, and the group signature scheme. The proposed collective signature schemes are built from these basic schemes. The correctness, security level and performance of the proposed schemes have also been presented in this paper.

The representative collective digital signature scheme allows the creation of a unique collective signature on document M that represents an entire signing community consisting of many individual signers and many different signing groups, each signing group is represented by a group leader. On document M, a collective signature can be created using the representative digital signature scheme that represents an entire community consisting of individual signers and signing groups, each of which is represented by a group leader. The characteristic of this type of letter is that it consists of three elements (U, E, S), one of which (U) is used to store the information of all the signers who participated in the formation of the collective signature on document M. While storing this information is necessary to identify the signer and resolve disputes later, it greatly increases the size of signatures. This is considered a limitation of the collective signature representing 3 elements. In this paper, we propose and build a new type of collective signature, a collective signature representing 2 elements (E, S). In this case, the signature has been reduced in size, but it contains all the information needed to identify the signer and resolve disputes if necessary. To construct the approved group signature scheme, which is the basic scheme for the proposed representative collective signature schemes, we use the discrete logarithm problem on the prime finite field. At the end of this paper, we present the security analysis of the AGDS scheme and a performance evaluation of the proposed collective signature schemes.

Due to the rapid development of new technologies, data security is one of the big challenges in today's world. Particularly, in the healthcare field, a large amount of data is generated every day. To maintain the patient personal records by manually and handling them, is not very sure, and Also avoiding the paperwork in the health care industry is not a good practice. As more records are stored electronically they need security and confidentiality. Different methods were proposed to prevent both internal and external threats in the healthcare industry. In healthcare industries record are extremely sensitive; therefore requires more security and privacy when storing and sharing of those records. The security as well as the privacy of sensitive health records are the major challenges in health care industries. To prevent unauthorized access to the healthcare records the user should be authenticated to get access to the records. To secure the data, cryptography techniques are used. The first is symmetric key encryption techniques which use only one key for both encryption and decryption of the data. Their design simple but can be easily cracked by using brute force attacks. On the other hand, the second is asymmetric key encryption techniques which use a pair of keys, one for encryption, and the other for decryption, whose security is higher as compared to the symmetric key encryption ones but lack in time efficiency. In our proposed system different access control mechanisms are used to provide security and confidentiality on healthcare records.

G-Merkle (GM) (PQCrypto 2018) is the first hash-based group signature scheme where it was stated that multi-tree approaches are not applicable, thus limiting the maximum number of supported signatures to 2 20. DGM (ESORICS 2019) is a dynamic and revocable GM-based group signature scheme that utilizes a computationally expensive puncturable encryption for revocation and requires interaction between verifiers and the group manager for signature verification. In this paper, we propose GM MT , a hash-based group signature scheme that provides solutions to the aforementioned challenges of the two schemes. GM MT builds on GM and adopts a multi-tree construction that constructs new GM trees for new signing leaves assignment while keeping the group public key unchanged, Compared to a single GM instance which enables 2 20 signature, GM MT allows growing the multi-tree structure adaptively to support 2 64 signatures under the same public key. Moreover, GM MT has a revocation mechanism that attains linkable anonymity of revoked signatures and has a logarithmic verification computational complexity compared to the linear complexity of DGM. The group manager in GM MT requires storage that is linear in the number of members while the corresponding storage in DGM is linear in the number of signatures supported by the system. Concretely, for a system that supports 2 64 signatures with 2 15 members and provides 256-bit security, the required storage of the group manager is 1 MB (resp. 10 8.7 TB) in GM MT (resp. DGM).

Recently non-abelian groups have attracted the atten- tion of cryptographers for constructing public-key cryp- tographic protocols. In this paper we use the conju- gacy problem in non-abelian groups to construct a zero- knowledge undeniable signature scheme. a more efficient alternative to well established numeric computations in abelian groups. Where as the secu- rity of cryptographic protocols based on number-theoretic abelian groups are based on the hardness of problems like integer factorization and discrete logarithm, the se- curity of cryptographic protocols based on non-abelian groups are based on the hardness of problems like conju- gacy search, decomposition and root problem. Almost all the undeniable signature schemes constructed so far have been based on the hardness of integer factorization (10) and discrete logarithm problems (6, 7). In this paper, we present a zero-knowledge undeniable signature scheme based on the hardness of the conjugacy problem in non- abelian grou...

In group signature schemes, one of the important issues is the member revocation, and lots of revocable schemes have been proposed. Recently, Group Signature scheme with Probabilistic Revocation (GSPR) is proposed. In GSPR, by employing a novel notion of probabilistic revocation, the computation cost of the revocation check is drastically reduced, although the correctness of the check is with a certain probability. However, in the GSPR scheme, there is another problem: m alias tokens are embedded into the certificate of a member. Then, in signing, each token is used, and O(m) exponentiations are needed to prove that the used token is embedded in the certificate. When m is large, this signing cost including O(m) exponentiations becomes a big problem for powerless mobile devices. In this paper, we propose an extended GSPR scheme where the signing cost is reduced, but the revocation mechanism is exactly the same as the original GSPR scheme. Our main idea is to utilize an efficient pairing-based accumulator with multiplications to embed lots of alias tokens in a certificate. Thus, in the proposed scheme, the signing cost is reduced to only O(m) multiplications instead of O(m) exponentiations.

Artin's braid groups have been recently suggested as a new source for public-key cryptography. In this paper we propose the first group signature schemes based on the conjugacy problem, decomposition problem and root problem in the braid groups which are believed to be hard problems.

Recently non-abelian groups have attracted the atten- tion of cryptographers for constructing public-key cryp- tographic protocols. In this paper we use the conju- gacy problem in non-abelian groups to construct a zero- knowledge undeniable signature scheme. a more efficient alternative to well established numeric computations in abelian groups. Where as the secu- rity of cryptographic protocols based on number-theoretic abelian groups are based on the hardness of problems like integer factorization and discrete logarithm, the se- curity of cryptographic protocols based on non-abelian groups are based on the hardness of problems like conju- gacy search, decomposition and root problem. Almost all the undeniable signature schemes constructed so far have been based on the hardness of integer factorization (10) and discrete logarithm problems (6, 7). In this paper, we present a zero-knowledge undeniable signature scheme based on the hardness of the conjugacy problem in non- abelian grou...

In this work we propose the first code-based group signature. As it will be described below, its security is based on a relaxation of the model of Bellare, Shi and Zhang [3] (BSZ model) verifying the properties of anonymity, traceability and non-frameability. Furthermore, it has numerous advantages over all existing post-quantum constructions and even competes (in terms of properties) with pairing based constructions: it allows to dynamically add new members and signature and public key sizes are constant with respect to the number of group members. Last but not least, our scheme can be extended into a traceable signature according to the definition of Kiayias, Tsiounis and Yung [19] (KTY model) and handles membership revocation. The main idea of our scheme consists in building a collision of two syndromes associated to two different matrices: a random one which enables to build a random syndrome from a chosen small weight vector; and a trapdoor matrix for the syndrome decoding problem, which permits to find a small weight preimage of the previous random syndrome. These two small weight vectors will constitute the group member's secret signing key whose knowledge will be proved thanks to a variation of Stern's authentication protocol. For applications, we consider the case of the code-based CFS signature scheme [11] of Courtois, Finiasz and Sendrier.

Partially-blind signatures find many applications in the area of anonymity, such as in e-cash or e-voting systems. They extend classical blind signatures, with a signed message composed of two parts: a public one (common to the user and the signer) and a private one (chosen by the user, and blindly signed). The signer cannot link later the message-signature to the initial interaction with the user, among other signatures on messages with the same public part. This paper presents a one-round partially-blind signature which achieves perfect blindness in the standard model using a Common Reference String, under classical assumptions: CDH and DLin assumptions in symmetric groups, and similar ones in asymmetric groups. This scheme is more efficient than the previous ones: reduced round complexity and communication complexity, but still weaker complexity assumptions. A great advantage is also to end up with a standard Waters signature, which is quite short. In addition, in all the previous schemes, the public part required a prior agreement between the parties on the public part of the message before running the blind signature protocol. Our protocol does not require such pre-processing: the public part can be chosen by the signer only. Our scheme even allows multiple messages provided from independent sources to be blindly signed. These messages can either be concatenated or aggregated by the signer, without learning any information about them, before returning the blind signature to the recipient. For the aggregation (addition of the messages), we provide a new result, of independent interest, about the Waters hash function over non binary-alphabets.

In 2008, Groth and Sahai proposed a powerful suite of techniques for constructing non-interactive zero-knowledge proofs in bilinear groups. Their proof systems have found numerous applications, including group signature schemes, anonymous voting, and anonymous credentials. In this paper, we demonstrate that the notion of smooth projective hash functions can be useful to design round-optimal privacy-preserving interactive protocols. We show that this approach is suitable for designing schemes that rely on standard security assumptions in the standard model with a common-reference string and are more efficient than those obtained using the Groth-Sahai methodology. As an illustration of our design principle, we construct an efficient oblivious signature-based envelope scheme and a blind signature scheme, both round-optimal.

We propose in this paper a security protocol based on periodic change of pseudonyms. The idea is to avoid illegal traceability of vehicles during their communications and preserve their privacy and confidential information. Two different approaches are proposed. In the first approach, each vehicle asks the central authority a new communication pseudonym after a time t. While in the second approach, each vehicle generates itself after a time t, a new communication pseudonym. Our objective is to permit at least two vehicles to change their pseudonym in the same time interval. We evaluate in this work, the bandwidth used by considering the vehicles speed in each approach. The proposed protocol is based on equidistant distribution of the road side unit and uses the average of speed permitted on the road to evaluate lifetime t of the communication's pseudonyms and certificates. The exchange of information is based on asymmetric and symmetric cryptography scheme and it uses hash function. Our protocol provides authentication, non-repudiation and privacy.

As the next generation of computing technology, as per customer demand and requirements, cloud computing offers the flexibility to dynamically add new resources and services. An increasing number of people and organizations are now able to shift their services to the cloud due to the rapidly evolving technology that supports cloud computing. Even though cloud computing is making rapid progress, security continues to be a major barrier to adoption. The adoption of cloud computing is seen as having been affected by the constant problem of data security. Challenges with data privacy, integrity, and trust are among the serious security concerns that are directing the wide adoption of cloud computing. One of the best ways to protect cloud storage is through cryptography. The problems of data integrity, privacy, and trust must be considered, and a number of algorithms and protocols have been created and are currently utilized. However, they are ineffective. Hence, to develop an effective cloud storage system, privacy-preserving cloud computing for data storage security frameworks using regenerating Homomorphic encryption is presented. Utilizing homomorphic encryption, data is transformed into ciphertext so that it can be studied and utilized in its original state. Encryption and decryption are the primary focus of this framework, which provides cloud users with data security assurance.

We introduce a lattice-based group signature scheme that provides several noticeable improvements over the contemporary ones: simpler construction, weaker hardness assumptions, and shorter sizes of keys and signatures. Moreover, our scheme can be transformed into the ring setting, resulting in a scheme based on ideal lattices, in which the public key and signature both have bit-size O(n • log N), for security parameter n, and for group of N users. Towards our goal, we construct a new lattice-based cryptographic tool: a statistical zero-knowledge argument of knowledge of a valid message-signature pair for Boyen's signature scheme (Boyen, PKC'10), which potentially can be used as the building block to design various privacy-enhancing cryptographic constructions.

The increasing growth of storage data in the cloud and virtual reality allows it a significant challenge to maintain the security of data that is outsourced by the data owners. The existing protocols for the auditing of cloud storage normally use post-quantum cryptography to monitor data integrity to solve this issue. Nevertheless, these protocols use strong cryptography to create data tags that reduce their reliability and extensibility. In this research work, we propose a novel protocol named "Advanced Distribution Verification Protocol (ADVP)" to design secure cloud storage to track the quality of cloud-saved data with the help of "Multiple-Third Party Auditors" (mTPAs) and not a "Single-TPA" (sTPA). This protocol requires several SUBTPAs that operate throughout the single TPA, which then needs to be spread equally throughout the SUBTPAs to guarantee that every SUBTPA is checked throughout the entire section. It then has strict safety evidence of mal...

In 2005 I. Anshel, M. Anshel, D. Goldfeld, and S. Lemieux introduced E-Multiplication, a quantum-resistant, group-theoretic, one-way function which can be used as a basis for many different cryptographic applications. To date, all analysis and attacks on E-Multiplication have been exponential in their runtime and all have been readily addressed and defeated. This paper introduces WalnutDSA, a new E-Multiplication-based public-key digital signature method that provides very efficient verification, allowing low-powered and constrained devices to quickly and inexpensively validate digital signatures (e.g., a certificate or authentication). This paper presents an in-depth discussion of the construction of the digital signature algorithm, analyzes the security of the scheme, provides a proof of security under EUF-CMA, and discusses the practical results from implementations on several constrained devices. With the implementation of parameters that defeat all known attacks, WalnutDSA is c...

As the next generation of computing technology, as per customer demand and requirements, cloud computing offers the flexibility to dynamically add new resources and services. An increasing number of people and organizations are now able to shift their services to the cloud due to the rapidly evolving technology that supports cloud computing. Even though cloud computing is making rapid progress, security continues to be a major barrier to adoption. The adoption of cloud computing is seen as having been affected by the constant problem of data security. Challenges with data privacy, integrity, and trust are among the serious security concerns that are directing the wide adoption of cloud computing. One of the best ways to protect cloud storage is through cryptography. The problems of data integrity, privacy, and trust must be considered, and a number of algorithms and protocols have been created and are currently utilized. However, they are ineffective. Hence, to develop an effective cloud storage system, privacy-preserving cloud computing for data storage security frameworks using regenerating Homomorphic encryption is presented. Utilizing homomorphic encryption, data is transformed into ciphertext so that it can be studied and utilized in its original state. Encryption and decryption are the primary focus of this framework, which provides cloud users with data security assurance.

This paper presents a privacy-preserving identity management system, referred to as Pima. The proposed system is built over a novel unlinkable malleable signature scheme, called UMS. Pima supports pseudonymity, as it is more in line with today's web service interactions than anonymity. The originality of the approach is manifold. First, Pima satisfies both users' and providers' basic security and privacy needs as it provides a user centric approach which permits the users to keep control over their revealed attributes, and the service providers to get attributes certified by an identity provider and associated with different pseudonymous sessions. Second, Pima helps service providers to comply with the data minimization principle required by the E.U. General Data Protection Regulation, through the enforcement of both sanitizable and redactable features. Third, the proposed signature scheme UMS fulfills main security and strong privacy requirements at a constant pairing computation overhead. Fourth, Pima's concrete construction is proven as secure under the generic group model. Fifth, the implementation results demonstrate high efficiency w.r.t. most closely related work, while considering resource-constrained devices, i.e., Android-10 smartphone.

Security and protection of private user information are a prerequisite for the deployment of the mobile network technologies.Nevertheless, the establishment of secure communication architecture within mobile ad hoc networks addresses special challenges, due to the characteristic and specific cities of such environment (high dynamic and mobility of nodes, high rate of topology changes, high variability in nodes density and neighbourhood, broad-cast/geocast communication nature).. A number of secure authentication schemes based on asymmetric cryptography have been proposed to prevent such attacks. In this paper, we address some interesting issues arising in such MANETs by designing an anonymous routing framework (ALERT) extended to key server management and group signature algorithm. It uses nodes' current locations to construct a secure MANET map. Based on the current map, each node can decide which other relay nodes it wants to communicate with. ALERT takes advantage of some advanced cryptographic primitives to achieve node authentication, data integrity, anonymity and untraceability (tracking-resistance). It also offers resistance to certain insider attacks.

A Sybil attack consists of an adversary assuming multiple identities to defeat the trust of an existing reputation system. When Sybil attacks are launched in vehicular networks, the mobility of vehicles increases the difficulty of identifying the malicious vehicle location. In this paper, a novel protocol for Sybil detection in vehicular networks is presented. Considering that vehicular networks are cyber-physical systems, the technique exploits well grounded results in the physical (i.e., transportation) domain to detect the Sybil attacks in the cyber domain. Compared to existing works that rely on additional cyber hardware support, or complex cryptographic primitives for Sybil detection, the protocol leverages the theory of platoon dispersion that models the physics of naturally occurring vehicle dispersion. Specifically, the proposed technique employs a certain number of roadside units that periodically collect reports from vehicles regarding their physical neighborhood. Leveragi...

Secure group communications present a unique environment where there can be multiple clients and hosts are trying to communicate securely within the group. As the number of clients and hosts increases the complexity of the communication security also increases. Group communications are based on a dynamic environment where the clients may join or leave the group at any moment. Hence it is important to ensure that only permitted entities have access to the group and those that have left the group or are not part of the group have no access to the group communications. This paper explores the delineation of a secure communication filter function that is applicable to group communications and is based on the latest Integrated Circuits Metrics (ICMetrics). The proposed scheme is based on the use of hash functions. To test the scalability of the scheme it has been implemented using SHA1 and SHA2.

a violação da desigualdade de Clauser-Horne-Shimony-Holt na prática. Após realizar o experimento, usaram os dados na desigualdade e concluíram que a desigualdade, obtida por meio de argumentos probabilísticos, era violada, confirmando as conclusões obtidas por John S. Bell de que não era possível uma teoria de variáveis ocultas nas condições propostas por Einstein, Podolsky e Rosen. O objetivo deste trabalho é observar a validade das fórmulas nas

Vehicular ad-hoc networks (VANETs) are a promising communication scenario. Several new applications are envisioned, which will improve traffic management and safety. As VANETs present some unique features (e.g. high mobility of nodes, geographic extension, etc.) traditional security mechanisms are not always suitable. The main intention of this network is to send and receive messages from the vehicles. VANETs follow the concept of Public Key Infrastructure (PKI) and Certificate Revocation Lists (CRL) for enhancing security. It can be achieved by intensifying the process carried out in Message Authentication Code (MAC). Through this, it is obvious that the security can be made efficient and processed faster than the existing schemes.

Code-based cryptography has a long history but did suffer from periods of slow development. The field has recently attracted a lot of attention as one of the major branches of post-quantum cryptography. However, its subfield of privacy-preserving cryptographic constructions is still rather underdeveloped, e.g., important building blocks such as zeroknowledge range proofs and set membership proofs, and even proofs of knowledge of a hash preimage, have not been known under code-based assumptions. Moreover, almost no substantial technical development has been introduced in the last several years. This work introduces several new code-based privacy-preserving cryptographic constructions that considerably advance the state-of-the-art in code-based cryptography. Specifically, we present 3 major contributions, each of which potentially yields various other applications. Our first contribution is a code-based statistically hiding and computationally binding commitment scheme with companion zero-knowledge (ZK) argument of knowledge of a valid opening that can be easily extended to prove that the committed bits satisfy other relations. Our second contribution is the first code-based zero-knowledge range argument for committed values, with communication cost logarithmic in the size of the range. A special feature of our range argument is that, while previous works on range proofs/arguments (in all branches of cryptography) only address ranges of non-negative integers, our protocol can handle signed fractional numbers, and hence, can potentially find a larger scope of applications. Our third contribution is the first code-based Merkle-tree accumulator supported by ZK argument of membership, which has been known to enable various interesting applications. In particular, it allows us to obtain the first code-based ring signatures and group signatures with logarithmic signature sizes.

We introduce a lattice-based group signature scheme that provides several noticeable improvements over the contemporary ones: simpler construction, weaker hardness assumptions, and shorter sizes of keys and signatures. Moreover, our scheme can be transformed into the ring setting, resulting in a scheme based on ideal lattices, in which the public key and signature both have bit-size O(n • log N), for security parameter n, and for group of N users. Towards our goal, we construct a new lattice-based cryptographic tool: a statistical zero-knowledge argument of knowledge of a valid message-signature pair for Boyen's signature scheme (Boyen, PKC'10), which potentially can be used as the building block to design various privacy-enhancing cryptographic constructions.

Groups can be formed as a fixed or static set or as a varying or dynamic set. Previously, no researcher considered groups, other than the two configurations. Yet, a new method is the formation of groups and the signatures, based on demand approach, which non trivializes the issue. By considering groups as virtual, issues of scalability, revocation rights of members, memory area for storage of private key for each member, etc, are addressed. The dynamic characteristics of private key, public key, partial signatures of individual members, as well as the group as an entity are factors. The generation of signatures by a group member is with its private key and the groups partial signature. This arrangement facilitates many advantages such as scalability, revocation, tracing, man-in-the-middle attacks, space requirements, and multiple keys of the group members. Even so, the procedure is adaptable for cloud computing, group communication as in banks to access group accounts with group signatures, group mobile communication, etc. This framework automates the banking system completely.

SummaryGroups can be formed as a fixed or static set or as a varying or dynamic set. Previously, no researcher considered groups, other than the two configurations. Yet, a new method is the formation of groups and the signatures, based on demand approach, which non trivializes the issue. By considering groups as virtual, issues of scalability, revocation rights of members, memory area for storage of private key for each member, etc, are addressed. The dynamic characteristics of private key, public key, partial signatures of individual members, as well as the group as an entity are factors. The generation of signatures by a group member is with its private key and the groups partial signature. This arrangement facilitates many advantages such as scalability, revocation, tracing, man‐ in‐the‐middle attacks, space requirements, and multiple keys of the group members. Even so, the procedure is adaptable for cloud computing, group communication as in banks to access group accounts with g...

Traditional (physical) access control systems are well-established mechanisms, allowing organizations to determine who should be able to access which physical space. This can either be a facility such as a critical infrastructure with a well-defined set of individuals, e.g., employees, or public spaces where everyone can be subject to access control. During the Covid-19 pandemic, additional features to reduce the risks of individuals when entering spaces became popular or even mandatory, including automatic scanning for protective wear (e.g., whether an individual wears a mask), body temperature checks, or digital health certificates, certifying that one has been negatively tested for, or vaccinated against, Covid-19. We refer to this as risk-based access control (RiBAC). In the Covid-19 pandemic largely due to the time pressure for implementing these measures, many of such RiBAC extensions to classical AC systems required manual intervention. This, besides posing health risks for the individuals performing these checks, yields a solution which is not scalable. Now that the Covid-19 pandemic no longer constitutes a public health emergency of international concern by the World Health Organization (WHO), it is time to reconsider RiBAC systems. Our main focus in this work is to investigate requirements for such systems and to discuss possible generic architectures for RiBAC systems. In order to be prepared for a future pandemic, the goal should be to implement such systems in a way such that they are scalable and risk-minimizing. We will specifically focus on privacy of the individuals subject to access control in RiBAC, while preserving the functionality of the system. Moreover, our focus is on the European setting where digital health certificates were considered as a central risk-reducing mechanism. In this context, we discuss the use of privacy-preserving cryptography in order to be able to have RiBAC systems that are privacy-preserving already in place for any potential future pandemic. This work is licensed under a Creative Commons Attribution International 4.0 License.

In 2008, Groth and Sahai proposed a general methodology for constructing non-interactive zero-knowledge (and witness-indistinguishable) proofs in bilinear groups. While avoiding expensive NP-reductions, these proof systems are still inefficient due to the number of pairing computations required for verification. We apply recent techniques of batch verification to the Groth-Sahai proof systems and succeed to improve significantly the complexity of proof verification. We give explicit batch-verification formulas for generic Groth-Sahai equations (whose cost is less than a tenth of the original) as well as for specific popular protocols relying on their methodology (namely Groth's group signatures and the P-signatures by Belenkiy, Chase, Kohlweiss and Lysyanskaya).