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Quantum secret sharing (QSS) is a fundamental primitive in quantum cryptography. The existing QSS protocols are either (n,n)-threshold or (t,n)-threshold access structure, where n denotes the number of players and t denotes the threshold number of players. Here, we introduce a novel verifiable QSS scheme that executes a restricted hyperstar access structure by using entangled states. Our method involves encoding selected quantum states and their corresponding measurements to yield outcomes of either + 1 or − 1. Furthermore, we give the validation of the scheme through the system of equations derived from the measurements, which then guarantees the honesty of the participants. At last, we also analyze the security of our scheme in two primary quantum attacks, such as external attacks and internal attacks. [ABSTRACT FROM AUTHOR]

There are perfect and ideal threshold secret sharing schemes, for example, Shamir’s secret sharing scheme. For the case of general secret sharing schemes with an arbitrary access structure, it is possible to construct a perfect scheme for any access structure (for example, the Ito – Saito – Nishizeki scheme, the Benaloh – Leichter scheme), but in general, such a scheme will not be an ideal secret sharing scheme. In the paper, for some classes of access structures, the construction of perfect and ideal secret sharing schemes based on linear codes is given. We also give a construction of perfect verifiable secret sharing schemes for any access structure for which there is a line code that implements this structure.

Sharing confidential information is a critical concern in today's world. Secret sharing schemes facilitate the sharing of secrets in a way that ensures only authorized participants (shareholders) can access the secret using their allocated shares. Hierarchical secret sharing schemes (HSSSs) build upon Shamir's scheme by organizing participants into different levels based on priority. Within HSSS, participants at each level can reconstruct the secret if a specified number, denoted as the threshold value (t), or more of them are present. Each level has a predetermined threshold value. If the number of participants falls below the threshold at any level, higher-level participants must be involved in reconstructing the secret at lower levels. Our paper proposes schemes that implement hierarchical access structures and enable the sharing of multiple secrets. Additionally, our proposed scheme includes share verification. We have analyzed potential attacks and demonstrated the scheme's resistance against them. Through security analysis and comparison with existing schemes, we highlight the novelty and superiority of our proposed approach, contributing to advancements in secure information-sharing practices. [ABSTRACT FROM AUTHOR]

The modern medical system is convergence of cutting-edge technologies and advancements in the healthcare environment. In the modern medical system, the storage of electronic health records is generally leased out to third-party cloud service providers (CSPs). But, CSPs cannot be entirely relied upon due to the potential security and privacy issues. This article presents Multi-Authority and Hierarchical Attribute-Based Encryption Scheme (MH-ABE) scheme to promote secure information sharing and protect patient's privacy. The utilization of CP-ABE in conjunction with multiple Attribute Authorities within the proposed MH-ABE scheme presents a scalable and fine-grained approach to data access control. The proposed MH-ABE scheme incorporates the utilization of a Hierarchical Access Tree to effectively encrypt numerous files concurrently, hence reducing the computational and storage cost. The proposed scheme has also been evaluated using a comparative analysis with existing schemes, emphasizing the assessment of computational and storage costs. The findings of this analysis demonstrate improved performance and efficiency of the proposed ciphertext policy based encryption scheme. The proposed MH-ABE scheme incorporates features such as policy hiding and revocation, and it exhibits resilience against attacks, including collusion resistance, Indistinguishability under chosen-plaintext attack and forward secrecy. [ABSTRACT FROM AUTHOR]

—In order to provide access control on encrypted data, Attribute-based encryption (ABE) defines each user using a set of attributes. Fuzzy identity-based encryption (FIBE) is a variant of ABE that allows for a threshold access structure for users. To address the potential threat posed by future quantum computers, this paper presents a postquantum fuzzy IBE scheme based on lattices. However, current lattice-based ABE schemes face challenges related to computational complexity and the length of ciphertext and keys. This paper aims to improve the performance of an existing fuzzy IBE scheme by reducing key length and computational complexity during the encryption phase. While negative attributes are not utilized in our scheme, we prove its security under the learning with error (LWE) hard problem assumption in the selective security model. These improvements have significant implications for the field of ABE.

In this paper, we propose a novel verifiable quantum secret sharing scheme tailored for a specific class of low-density parity-check (LDPC) codes. In the proposed protocol, Alice, the dealer, initially utilizes the generator matrix of the chosen LDPC code to calculate all secret shares and distributes individual shares to all participants in a quantum secure direct communication channel. In the distribution phase, each participant computes a hash value based on their respective share and a randomly generated sequence, which is then published. In the recover phase, each participant performs a unitary operation on these received particles and sends them to the next participant using the decoy-photon technique. Furthermore, the last participant performs Bell measurements on the final quantum states to obtain the original secret. At last, we demonstrate our protocol to be secure against intercept-and-resend attack, entangle-and-measure attack and dishonest participant attack. In addition, we present a comparison of our protocol with other existing schemes. [ABSTRACT FROM AUTHOR]

In order to provide access control on encrypted data, Attribute-based encryption (ABE) defines each user using a set of attributes. Fuzzy identity-based encryption (FIBE) is a variant of ABE that allows for a threshold access structure for users. To address the potential threat posed by future quantum computers, this paper presents a postquantum fuzzy IBE scheme based on lattices. However, current lattice-based ABE schemes face challenges related to computational complexity and the length of ciphertext and keys. This paper aims to improve the performance of an existing fuzzy IBE scheme by reducing key length and computational complexity during the encryption phase. While negative attributes are not utilized in our scheme, we prove its security under the learning with error (LWE) hard problem assumption in the selective security model. These improvements have significant implications for the field of ABE. [ABSTRACT FROM AUTHOR]

Sharing confidential information is a critical concern in today’s world. Secret sharing schemes facilitate the sharing of secrets in a way that ensures only authorized participants (shareholders) can access the secret using their allocated shares. Hierarchical secret sharing schemes (HSSSs) build upon Shamir’s scheme by organizing participants into different levels based on priority. Within HSSS, participants at each level can reconstruct the secret if a specified number, denoted as the threshold value (t), or more of them are present. Each level has a predetermined threshold value. If the number of participants falls below the threshold at any level, higher-level participants must be involved in reconstructing the secret at lower levels. Our paper proposes schemes that implement hierarchical access structures and enable the sharing of multiple secrets. Additionally, our proposed scheme includes share verification. We have analyzed potential attacks and demonstrated the scheme’s resistance against them. Through security analysis and comparison with existing schemes, we highlight the novelty and superiority of our proposed approach, contributing to advancements in secure information-sharing practices.

Quantum multi-secret sharing plays a vital role in secure multi-key management. In this paper, an authenticable quantum multi-secret sharing scheme based on monotone span program is proposed. In our scheme, the distributor/participants run a quantum state digital signature algorithm to identify dishonest participants, strengthening the proposed scheme's security. During the reconstruction phase, the participants encode their shares onto the generalized Bell states with the generalized Pauli operator to reconstruct multiple secrets. Here, the phase shift operator is utilized to share d-dimensional quantum states. Furthermore, security analysis shows that the proposed scheme can resist the entangle-measure attack, intercept-resend attack, and common internal attacks such as forgery attack, collusion attack, and denial attack. [ABSTRACT FROM AUTHOR]

In order to solve the key security problem in attribute-based encryption, a ciphertext policy attribute-based encryption scheme against key abuse was proposed based on the ring learning with error over ring and the access structure of ordered binary decision diagram.Firstly, two different institutions were constructed to jointly generate the user’s secret key, which reduced the risk of key disclosure by institutions.Secondly, the user’s specific information was embedded in each secret key to realize the traceability of the key, and the access of illegal users and malicious users were avoided by maintaining the white list.In addition, the access structure of ordered binary decision diagram was adopted by the proposed scheme, and the positive and negative values of attributes on the basis of supporting attribute AND, OR and Threshold operation were increased.Analysis shows that the proposed scheme meets the distinguishable security of anti-collusion attack and chosen-plaintext attack, reduces the storage and computing overhead, and it is more practical than other schemes.

The Internet of Things (IoT) is a new technology that has drawn interest from both industry and academia in the modern digital era. The IoT provides a platform for any device to connect and share data over the Internet. Because of the diverse IoT environment and resource-constrained IoT devices, this nascent technology has numerous security challenges. Due to the lack of fine-grained access control and flexibility, traditional cryptographic algorithms such as private key encryption and public-key encryption are not suitable for providing access control mechanisms. ABE (Attribute-Based Encryption) is a new cryptographic approach that not only provides security but also fine-grained access control. This paper provides a comprehensive survey of ABE and its various forms, such as key policy ABE and ciphertext policy ABE, based on access structure, multi-authority, and hierarchy features. Further access structures used in ABE and applications of the ABE technique in IoT are also discussed. A comparison of different ABE schemes is presented regarding features, efficiency, and security. In addition, numerous schemes are analyzed to uncover obstacles, issues, and gaps that need to be investigated further. [ABSTRACT FROM AUTHOR]

In order to solve the key security problem in attribute-based encryption, a ciphertext policy attribute-based encryption scheme against key abuse was proposed based on the ring learning with error over ring and the access structure of ordered binary decision diagram. Firstly, two different institutions were constructed to jointly generate the user's secret key, which reduced the risk of key disclosure by institutions. Secondly, the user's specific information was embedded in each secret key to realize the traceability of the key, and the access of illegal users and malicious users were avoided by maintaining the white list. In addition, the access structure of ordered binary decision diagram was adopted by the proposed scheme, and the positive and negative values of attributes on the basis of supporting attribute AND, OR and Threshold operation were increased. Analysis shows that the proposed scheme meets the distinguishable security of anti- collusion attack and chosen-plaintext attack, reduces the storage and computing overhead, and it is more practical than other schemes. [ABSTRACT FROM AUTHOR]

In cloud storage, data owners usually achieve confidentiality of information through giving encrypted data to the server and as a consequence, the possibility of searching over the database is lost. Searchable encryption (SE) is a method to encrypt data in such a way that keyword searching would still be possible. However, to the best of our knowledge, existing literature on SE schemes only supports search operations carried out by an individual users. In this paper, we introduce the concept of public key encryption with distributed keyword search (PEDKS) to provide a solution for scenarios where the search ability can be distributed among authorized subsets of users according to a predefined access structure. Therefore, by employing a PEDKS, group members realizing the specified access structure can cooperatively query to search. We further propose a concrete construction of a PEDKS scheme and prove its security under the intractability of ECDL and BDH problems. Performance analysis and comparison with related concepts are provided as well. [ABSTRACT FROM AUTHOR]

In this paper, we construct a physical process to mask the d-dimensional quantum state into multipartite quantum systems. According to this masker, we propose a quantum secret sharing scheme to realize a class of special hypergraph access structures. In the distribution phase of the proposed protocol, the distributor wants to share an unknown d-dimensional quantum state and mask the secret state into a multi-party quantum systems. In the reconstruction phase, participants in the authorized set carry out several measurements and a series of appropriate unitary operations on their particles to obtain the original information state. At last, we also analyze the security of our scheme in three primary quantum attacks. [ABSTRACT FROM AUTHOR]

Proxy re-encryption is an essential prerequisite that facilitates a foreign entity (e.g., cloud server) to enforce the access of provisions of a document extended by one user to another user. While performing this task it is essential that the foreign entity does not learn any information about the actual document inside the encrypted envelop. In this paper, we present a scheme on Privacy-preserving Proxy Re-encryption for Access Control in Public Cloud, termed as PAC, that provides the proxy re-encryption of attribute-based encrypted data with receiver privacy. The proposed PAC scheme enables a proxy server to perform the re-encryption operation without learning anything about the data or the access policy. The PAC provides data confidentiality, and preserves receiver privacy. We show the PAC scheme adaptively secure against indistinguishability of ciphertext policy and chosen-plaintext attack (IND-CP-CPA) under the 2-Decisional Bilinear Diffie-Hellman Inversion assumption. The scheme is implemented on Google cloud instance and the experimental results show that the PAC scheme is storage and computation-efficient when compared to other related schemes. [ABSTRACT FROM AUTHOR]

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Copyright of Lexikos is the property of Bureau of the Woordeboek van die Afrikaanse Taal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Authentication is an important primitive of cryptography. With the rapid progress of network communication, the urgent data needs to ensure it integrity and privacy, therefore, the authentication of multi-receiver has a significant impact on the development of network interaction. R. Safavi-Nalni and H. Wang showed that authentication scheme based on Reed-Solomon code is unconditionally secure and allows multiple messages to be authenticated, but the number of receiver to verify is less than q, where the messages are in Fq. In 2014, the secure multi-receiver authentication scheme base on linear code was proposed, however, this scheme can not realize any a given access structure. In this paper, we present a multireceiver authentication scheme to realize any a given ideal access structure, and demonstrate that our scheme is unconditionally secure and allows r messages to be authenticated with each receiver own private key.

Internet of Things (IoT) is a modern technology that is applicable almost everywhere nowadays. Everything is connected to the Internet in the modern digital era. IoT is a collection of things that are interconnected to share information. Devices connected to IoT networks have some limitations in performing heavy computational tasks because of the availability of less computational and battery power. Attribute Based Encryption (ABE) is a modern public-key cryptographic technique that provides privacy with access control. The bilinear map is an expensive operation that is used in most of the ABE schemes. Elliptic Curve Cryptography (ECC) is an alternative for bilinear pairing to reduce the computation of encryption and decryption in ABE schemes. The process of encryption and decryption of ABE is a heavy computational task for resource-constrained devices. In this paper, an outsourcing-based decryption of ABE using ECC is proposed to reduce the decryption overhead of devices that have limited computational resources. Our scheme divides the computation of the decryption of ABE into two stages: first, the partial decryption of ciphertext in the cloud server, and second, the final decryption of partially decrypted ciphertext by the data user to retrieve the original message. This scheme is secure against the malicious cloud server by adding a blinding factor into the secret to be shared. The blinding factor is shared with intended users through attribute authority. The experimental results demonstrate that our scheme can reduce the decryption complexity and save the computational time of devices, compared to the existing schemes. Thus the proposed scheme is applicable for lightweight devices used in IoT. [ABSTRACT FROM AUTHOR]

A group-characterizable (GC) random variable is induced by a finite group, called main group, and a collection of its subgroups. The notion extends directly to secret sharing schemes (SSSs). It is known that linear and abelian SSSs can be equivalently described in terms of GC SSSs. In this paper, we present a necessary and sufficient condition for a SSS to be equivalent to a GC one. Using this result, we show that homomorphic SSSs (HSSSs) are equivalent to GC SSSs whose subgroups are normal in the main group. We also present two applications for this equivalent description of HSSSs. One concerns lower bounding the information ratio of access structures for the class of HSSSs, and the other is about the coincidence between statistical, almost-perfect and perfect security notions for the same class. [ABSTRACT FROM AUTHOR]

Quantum secret sharing plays an important role in quantum cryptography. In this paper, we propose a new general quantum secret sharing scheme based on access structure and monotone span program. In our scheme, the secret distributor first distributes the secret share according to the access structure, and then each participant in the authorization set hides their secret share in the qubits, and then transmits each qubit safely performed on unitary transformation. Compared with the existing quantum secret sharing schemes, our scheme is more flexible, general and less computational cost in practical applications. [ABSTRACT FROM AUTHOR]

XOR-based Visual Cryptography System (XVCS) is developed to achieve high contrast and good resolution of the recovered secret image. In general (k,n) VCS, the secret image can be visualized only if k or more than k shares are stacked together. In (k,n,t)∗ access structure, t number of participants are considered as the essential participants(t ≤ k ≤ n) whose shares are absolutely necessary to reconstruct the secret image. Several methods have been already proposed for the construction of (k,n)∗ VCS for black and white images. The major focus of this work is to design an XVCS for (k,n,t)∗ access structure for both black and white images and color images with maximum contrast. The experimental outcome shows that the proposed method has better results than other techniques proposed so far. Also, numerical examples are provided for (k,n,t)∗ XVCS for t = 1 and 2. The XVCS designed for (k,n,t)∗ access structure can be used for any real time application and is demonstrated with an example of user authentication in banking system. [ABSTRACT FROM AUTHOR]

Cipher text-policy attribute-based encryption schema(CP-ABE) is widely used in protection of sensitive data.In CP-ABE,When the users access the cipher text,the access structure and the cipher text were sent to the users.However,the access structure is also has private information which can lead to leak of the privacy.The group signatures were used in CP-ABE to realize protection of the privacy.What’s more,it can satisfy indistinguishable under the choice of plaintext attack.

Cipher text-policy attribute-based encryption schema(CP-ABE) is widely used in protection of sensitive data. In CP-ABE, When the users access the cipher text, the access structure and the cipher text were sent to the users. However, the access structure is also has private information which can lead to leak of the privacy. The group signatures were used in CP-ABE to realize protection of the privacy.What’s more, it can satisfy indistinguishable under the choice of plaintext attack.

The purpose of this paper is to develop an algorithm for sharing k secret images to n participants in such a way that each participant gets a single share image by encoding all k images. Any qualified subgroup of t : t ≤ n of those n participants can reconstruct the kith secret image only by combining their share images if they are qualified to reconstruct the kith secret image. Most of the existing literature solves this problem for the cases where t = 2 or t = n making it a very restrictive scheme. In this article, we aim to design a multi-secret image sharing scheme based on XOR operation where t is not restricted to be 2 or n. We have used n random matrices of the same size as the secret image size as private share to generate r (where r is the number of qualified subgroups) share images as public share using XOR operations. The proposed scheme is computationally lightweight and lossless due to XOR operation only. It does not involve any pixel expansion. The experimental results with a very low correlation coefficient between share and secret images confirm that share image does not reveal anything about secret image. The scheme is secure against differential attack as a higher value of Number of Changing Pixel rate (NPCR) confirms that. The current proposal is based on a general access structure, and hence any secret image can be reconstructed by a qualified group of t or more shares where t need not be 2 or n only. [ABSTRACT FROM AUTHOR]

The increasing deployment of Internet of Things in diversified fields provides groundwork for smart living. However, at the same time, it brings challenges like security and privacy. Among the numerous proposed security schemes, attribute-based encryption (ABE) is considered as one of the most promising security and privacy preserving scheme in distributed environment (or cloud environment). Many variants of the ABE exist, but most of them employ the expensive bilinear pairing operations. In this article, we have proposed a lightweight elliptic-curve-cryptography-based key-policy ABE without bilinear pairing and having a feature of key refresh/update mechanism. Also, the key distribution is done by the authority, which incorporates direct attribute/user revocation. The scheme is secured under elliptic curve decisional Diffie–Hellman assumption. The performance analysis demonstrates that the proposed scheme is efficient as compared to the existing ABE schemes. [ABSTRACT FROM AUTHOR]

Ciphertext-policy attribute-based encryption (CP-ABE) is a promising cryptographic solution to the problem for enforcing fine-grained access control over encrypted data in the cloud. However, when applying CP-ABE to data outsourcing scenarios, we have to address the challenging issue of policy updates because access control elements, such as users, attributes, and access rules may change frequently. In this paper, we propose a notion of access policy updatable ciphertext-policy attribute-based encryption (APU-CP-ABE) by combining the idea of ciphertext-policy attribute-based key encapsulation and symmetric proxy re-encryption. When an access policy update occurs, data owner is no longer required to download any data for re-encryption from the cloud, all he needs to do is generate a re-encryption key and produce a new encapsulated symmetric key, and then upload them to the cloud. The cloud server executes re-encryption without decryption. Because the re-encrypted ciphertext is encrypted under a completely new key, users cannot decrypt data even if they keep the old symmetric keys or parts of the previous ciphertext. We present an APU-CP-ABE construction based on Syalim et al.’s [Syalim, Nishide and Sakurai (2017)] improved symmetric proxy re-encryption scheme and Agrawal et al.’s [Agrawal and Chase (2017)] attribute-based message encryption scheme. It requires only 6 bilinear pairing operations for decryption, regardless of the number of attributes involved. This makes our construction particularly attractive when decryption is time-critical. [ABSTRACT FROM AUTHOR]

With the development of cloud computing, more and more video services are moving to the cloud. How to realize fine-grained access control of those data on cloud becomes an urgent problem. Attribute-based encryption provides a solution. However, heavy computation is still a bottleneck restricting the wider application of attribute-based encryption in cloud computing. In addition, we find that expression of the access control structure on media cloud can be further improved. To solve these problems, we propose an enhanced media ciphertext-policy attribute-based encryption algorithm and introduce its two key components, the multiple access tree and the key chain. To increase the scalability of the proposed algorithm, we discussed the issues of multi-authorization, user revocation, and 1 − n multiple access tree. Security analysis shows that enhanced media ciphertext-policy attribute-based encryption can successfully resist chosen-plaintext attacks under the decisional bilinear Diffie–Hellman assumption. Performance analysis proves both theoretically and practically that the proposed algorithm incurs less computational cost than the traditional ciphertext-policy attribute-based encryption, multi-message ciphertext-policy attribute-based encryption, and scalable ciphertext-policy attribute-based encryption by optimizing the access control structure. Our proposed algorithm has strong practical significance in media cloud. [ABSTRACT FROM AUTHOR]

Cloud users are outsourcing their data day-by-day resulting in huge amount of data storage in Cloud server. Cloud service provider (CSP) themselves may go for modifying the data that leads to data integrity problem. Unauthorized users illegally gain access to the data stored in cloud server. Therefore, providing protection, achieving privacy and access control for user's data are big challenges in the Cloud. Ciphertext-policy attribute-based encryption (CP-ABE) is prominent encryption technique to solve the exigent dilemma of secure data sharing in cloud computing. The shared data files generally have the characteristic of multilevel hierarchy, predominantly in the areas of IT companies, healthcare and military; these areas require a multi-authority access control. However, the hierarchy construction of shared files and multi-authority access control approach are not been investigated in CP-ABE. This paper proposes an efficient multi-authority access control using attribute-based encryption scheme that achieves efficient, fine grained access control. The proposed scheme consists of one algorithm – (Role Hierarchy Algorithm (RHA) and Hierarchy Access Structure (HAS) to protect user's data, achieve privacy, multi-authority access control and fine grained access to a stored data. The RHA algorithm classifies Cloud users into groups based on their assigned attributes. The HAS helps to define an access structure for fine grained and multi-authority access control of Cloud resources. Simulation results prove that the proposed RHA, HAS are efficient (in terms of time consumption and storage consumption for encryption, decryption) compared to existing works. The advantages of proposed scheme become more and more conspicuous when there is more number of files at Cloud storage server. [ABSTRACT FROM AUTHOR]