Hierarchical Key Assignment Scheme Research Articles

Retracted: A Novel Hierarchical Key Assignment Scheme for Data Access Control in IoT

Retracted: A Novel Hierarchical Key Assignment Scheme for Data Access Control in IoT

A Hierarchical Key Assignment Scheme: A Unified Approach for Scalability and Efficiency

A Hierarchical Key Assignment Scheme: A Unified Approach for Scalability and Efficiency

Efficient dynamic key‐aggregate cryptosystem for secure and flexible data sharing

SummarySecure and efficient enforcement of dynamic access control policies on shared data is a central problem in dynamic and scalable application scenarios, including the Internet of Things and smart cities. Key‐aggregate cryptosystem (KAC) is an efficient mechanism to delegate decryption rights of a subset of a large collection of data items to authorized users. While KAC provides an efficient solution to the problem of secure data sharing, we identify that using it to enforce continuously changing access policies is highly inefficient. In this article, we propose a novel dynamic KAC that, in addition to satisfying all key‐aggregate efficiency requirements, enforces dynamic updates to the aggregate sets with constant computation and constant communication cost. We propose a concrete construction for our dynamic KAC, prove its soundness and formal security, and analyze its theoretical and practical performance. We implement the procedures of a dynamic hierarchical key assignment scheme using the proposed as well as the existing dynamic KACs. We compare the costs of enforcing dynamic updates in large hierarchies. We conclude that the performance enhancement achieved by the proposed dynamic KAC compared to the existing KACs is even more significant in practical access control scenarios.

Hierarchical Access Control in Cloud Computing

Access control is an essential security component of cloud computing, and hierarchical access management is of particular interest because different access privileges are granted in practice. As a solution to versatile and fine-grained hierarchical access control in cloud computing, this paper also presents a hierarchical key assignment scheme based on linear geometry. The encryption key of each class in the hierarchy is connected with a private vector and a public vector in our scheme, and the inner product of an ancestor class's private vector as well as the public variable of its decedent’s class could be used to deduce the encryption method of that descendant class. The proposed scheme is among the direct access strategies on hierarchical access control, which also means so each class at a higher level can straight derive this same encryption key of its decedent’s class without and need to iterate. In furthermore to this basic hierarchy key derivation, we propose a dynamic key management mechanism to handle possible changes in the hierarchy efficiently. Under the assumption of pseudo - random number functions, our scheme requires only light computations over a finite field by providing strong key in-distinguishability. Furthermore, the simulation demonstrates that our scheme maximises the trade-off among computation consumption as well as storage space.

A Novel Hierarchical Key Assignment Scheme for Data Access Control in IoT

Hierarchical key assignment scheme is an efficient cryptographic method for hierarchical access control, in which the encryption keys of lower classes can be derived by the higher classes. Such a property is an effective way to ensure the access control security of Internet of Things data markets. However, many researchers on this field cannot avoid potential single point of failure in key distribution, and some key assignment schemes are insecure against collusive attack or sibling attack or collaborative attack. In this paper, we propose a hierarchical key assignment scheme based on multilinear map to solve the multigroup access control in Internet of Things data markets. Compared with previous hierarchical key assignment schemes, our scheme can avoid potential single point of failure in key distribution. Also the central authority of our scheme (corresponding to the data owner in IoT data markets) does not need to assign the corresponding encryption keys to each user directly, and users in each class can obtain the encryption key via only a one-round key agreement protocol. We then show that our scheme satisfies the security of key indistinguishability under decisional multilinear Diffie-Hellman assumption. Finally, comparisons show the efficiency of our scheme and indicates that our proposed scheme can not only resist the potential attacks, but also guarantee the forward and backward security.

Extended hierarchical key assignment scheme (E-HKAS): how to efficiently enforce explicit policy exceptions in dynamic hierarchies

In this paper, we focus on practically motivated flexibility requirements for the hierarchical access control model, namely transitive exception and anti-symmetric exception. Additionally, we motivate a new flexibility requirement called “class delegation with descendant(s) safety” in a practical application scenario. We propose our extended hierarchical key assignment scheme (E-HKAS) that satisfies all three aforementioned flexibility requirements in a dynamic hierarchy of security classes. To propose a generic E-HKAS, we model the hierarchical access control policy as a collection of access groups. E-HKAS enforces transitive and anti-symmetric exceptions using an efficient group-based encryption scheme. To enforce class delegation with descendant(s) safety, we propose a novel cryptographic primitive called group proxy re-encryption (GPRE) that supports proxy re-encryption between two access groups. We present an IND-CPA-secure construction of our proposed GPRE scheme and formally prove its security. Performance analysis shows that the proposed E-HKAS enforces explicit transitive and anti-symmetric exceptions more efficiently than the existing approaches in the literature. Computation cost for key derivation is constant and does not depend on the depth of the hierarchy. Also, to enforce class delegation with descendant(s) safety, the proposed E-HKAS requires constant number of computational steps to be executed.

An efficient and provably secure time‐limited key management scheme for outsourced data

SummaryA time‐limited data access control scheme allows a user's access to the data files only for a specified time period. A cryptographic solution to the time‐limited access control problem is by encrypting each data group associated with a time period with a distinct key. The data is encrypted by the data owner. The respective decryption keys are then distributed to authorized users by the data owner. A user requires one secret decryption key storage for each authorized time period. To reduce the secret key storage with each user, time‐limited hierarchical key management schemes are generally used. Many such schemes are proposed in the recent years. The objective of these schemes is system efficiency and data security. Construction of such schemes become more challenging when data is outsourced to an untrusted third party service provider. In current work, an efficient and secure time‐limited hierarchical key assignment scheme is proposed for key management suitable for data outsourcing scenario. We compare it with the other recent similar schemes. The scheme is formally proved against the modern stronger security notion called key indistinguishability.

Cryptographic Hierarchical Access Control for Dynamic Structures

A hierarchical key assignment scheme is a method to assign some private information and encryption keys to a set of classes in a partially ordered hierarchy, in such a way that the private information of a higher class can be used to derive the keys of all classes lower down in the hierarchy. Sometimes, it is necessary to make dynamic updates to the hierarchy, in order to implement an access control policy which evolves with time. All security models for hierarchical key assignment schemes have been designed to cope with static hierarchies and do not consider the issue of performing dynamic updates to the hierarchy. In this paper, we define the concept of hierarchical key assignment schemes supporting dynamic updates, formalizing the relative security model. In particular, we provide the notion of security with respect to key indistinguishability, by considering the dynamic changes to the hierarchy. Moreover, we show how to construct a hierarchical key assignment scheme supporting dynamic updates, by using as a building block a symmetric encryption scheme. The proposed construction is provably secure with respect to key indistinguishability, and provides efficient key derivation and updating procedures, while requiring each user to store only a single private key.

Supporting dynamic updates in storage clouds with the Akl–Taylor scheme

With the wide diffusion of cloud technologies, an ever increasing amount of sensitive data is moved on centralized network-based repository services, providing elastic outsourced storage capacity, available through remote access. This introduces new challenges associated to the security and privacy of outsourced data that has to be dynamically created, shared, updated and removed by a large number of users, characterized by different access rights and views structured according to hierarchical roles.To address such challenges, and implement secure access control policies in those application domains, several cryptographic solutions have been proposed. In particular, hierarchical key assignment schemes represent an effective solution to deal with cryptographic access control. Starting from the first proposal due to Akl and Taylor in 1983, many hierarchical key assignment schemes have been proposed. However, the highly dynamic nature of cloud-based storage solutions may significantly stress the applicability of such schemes on a wide scale.In order to overcome such limitations, in this work we provide new results on the Akl–Taylor scheme, by carefully analyzing the problem of supporting dynamic updates, as well as key replacement operations. In doing this, we also perform a rigorous analysis of the Akl–Taylor scheme in the dynamic setting characterizing storage clouds, by considering different key assignment strategies and proving that the corresponding schemes are secure with respect to the notion of key recovery.

Key Indistinguishability versus Strong Key Indistinguishability for Hierarchical Key Assignment Schemes

A hierarchical key assignment scheme is a method to assign some private information and encryption keys to a set of classes in a partially ordered hierarchy, in such a way that the private information of a higher class can be used to derive the keys of all classes lower down in the hierarchy. In this paper we analyze the security of hierarchical key assignment schemes according to different notions: security with respect to key indistinguishability and against key recovery , as well as the two recently proposed notions of security with respect to strong key indistinguishability and against strong key recovery . We first explore the relations between all security notions and, in particular, we prove that security with respect to strong key indistinguishability is not stronger than the one with respect to key indistinguishability. Afterwards, we propose a general construction yielding a hierarchical key assignment scheme offering security against strong key recovery, given any hierarchical key assignment scheme which guarantees security against key recovery.

Achieving Simple, Secure and Efficient Hierarchical Access Control in Cloud Computing

Access control is an indispensable security component of cloud computing, and hierarchical access control is of particular interest since in practice one is entitled to different access privileges. This paper presents a hierarchical key assignment scheme based on linear-geometry as the solution of flexible and fine-grained hierarchical access control in cloud computing. In our scheme, the encryption key of each class in the hierarchy is associated with a private vector and a public vector, and the inner product of the private vector of an ancestor class and the public vector of its descendant class can be used to derive the encryption key of that descendant class. The proposed scheme belongs to direct access schemes on hierarchical access control, namely each class at a higher level in the hierarchy can directly derive the encryption key of its descendant class without the need of iterative computation. In addition to this basic hierarchical key derivation, we also give a dynamic key management mechanism to efficiently address potential changes in the hierarchy. Our scheme only needs light computations over finite field and provides strong key indistinguishability under the assumption of pseudorandom functions. Furthermore, the simulation shows that our scheme has an optimized trade-off between computation consumption and storage space.

Hierarchical and Shared Access Control

Access control ensures that only the authorized users of a system are allowed to access certain resources or tasks. Usually, according to their roles and responsibilities, users are organized in hierarchies formed by a certain number of disjoint classes. Such hierarchies are implemented by assigning a key to each class, so that the keys for descendant classes can be efficiently derived from classes higher in the hierarchy. However, pure hierarchical access may represent a limitation in many real-world cases. In fact, sometimes it is necessary to ensure access to a resource or task by considering both its directly responsible user and a group of users possessing certain credentials. In this paper, we first propose a novel model that generalizes the conventional hierarchical access control paradigm, by extending it to certain additional sets of qualified users. Afterward, we propose two constructions for hierarchical key assignment schemes in this new model, which are provably secure with respect to key indistinguishability. In particular, the former construction relies on both symmetric encryption and perfect secret sharing, whereas, the latter is based on public-key threshold broadcast encryption.

On the Equivalence of Two Security Notions for Hierarchical Key Assignment Schemes in the Unconditional Setting

The access control problem in a hierarchy can be solved by using a hierarchical key assignment scheme, where each class is assigned an encryption key and some private information. A formal security analysis for hierarchical key assignment schemes has been traditionally considered in two different settings, i.e., the unconditionally secure and the computationally secure setting, and with respect to two different notions: security against key recovery (KR-security) and security with respect to key indistinguishability (KI-security), with the latter notion being cryptographically stronger. Recently, Freire, Paterson and Poettering proposed strong key indistinguishability (SKI-security) as a new security notion in the computationally secure setting, arguing that SKI-security is strictly stronger than KI-security in such a setting. In this paper we consider the unconditionally secure setting for hierarchical key assignment schemes. In such a setting the security of the schemes is not based on specific unproven computational assumptions, i.e., it relies on the theoretical impossibility of breaking them, despite the computational power of an adversary coalition. We prove that, in this setting, SKI-security is not stronger than KI-security, i.e., the two notions are fully equivalent from an information-theoretic point of view.

A Robust Time-Bound Hierarchical Key Assignment Scheme

Recently, Chien proposed a time-bound hierarchical key assignment scheme based on tamper-resistant devices, which improves the performance in terms of the computational efforts and the implementation costs. Later, Santis et al. demonstrated a collusion attack on Chien's scheme to show that collusive malicious insiders can cooperatively derive some encryption keys and further proposed an improvement to eliminate the security flaws inherent in Chien's scheme. In this paper, we will prove that Santis et al.'s key derivation is incorrect and their claimed security requirements cannot be achieved. On the other hand, we will further propose a new key derivation to improve the weakness in Santis et al., scheme.

An Efficient Solution for Hierarchical Access Control Problem in Cloud Environment

The time-bound hierarchical key assignment scheme provides a cryptographic solution for the access control problem in distributed systems (e.g., Pay-TV and cloud computing applications). Most time-bound hierarchical key assignment schemes can be divided into two types: adopting tamper-resistant devices and utilizing public values. Despite the fact that adopting tamper-resistant devices can easily resist to collusion attacks, utilizing public values is much cheaper and more suitable for cloud environment. In this paper, we proposed a new time-bound hierarchical key assignment scheme, which can effectively defeat the collusion attack. Besides, the proposed scheme utilizes public values instead of tamper-resistant devices, which will restrict user’s convenience. Compared with the previous works, our scheme requires fewer public values and has better performance.

A note on time-bound hierarchical key assignment schemes

A time-bound hierarchical key assignment scheme is a method to assign time-dependent encryption keys to a set of classes in a partially ordered hierarchy, in such a way that each class can compute the keys of all classes lower down in the hierarchy, according to temporal constraints.In this paper we consider the unconditionally secure setting for time-bound hierarchical key assignment schemes and distinguish between two different goals: security with respect to key indistinguishability and against key recovery. We first present definitions of security with respect to both goals; then, we prove a tight lower bound on the size of the private information distributed to each class; finally, we show an optimal construction for time-bound hierarchical key assignment schemes.

Efficient provably-secure hierarchical key assignment schemes

A hierarchical key assignment scheme is a method to assign some private information and encryption keys to a set of classes in a partially ordered hierarchy, in such a way that the private information of a higher class can be used to derive the keys of all classes lower down in the hierarchy. In this paper we design and analyze hierarchical key assignment schemes which are provably secure and support dynamic updates to the hierarchy with local changes to the public information and without requiring any private information to be re-distributed. – We first consider the problem of constructing a hierarchical key assignment scheme by using as a building block a symmetric encryption scheme. We propose a new construction which is provably secure with respect to key indistinguishability, requires a single computational assumption, and improves on previous proposals. – Then, we show how to construct a hierarchical key assignment scheme by using as a building block a public-key broadcast encryption scheme. In particular, one of our constructions provides constant private information and public information linear in the number of classes in the hierarchy.

Provably-Secure Time-Bound Hierarchical Key Assignment Schemes

A time-bound hierarchical key assignment scheme is a method to assign time-dependent encryption keys to a set of classes in a partially ordered hierarchy, in such a way that each class can compute the keys of all classes lower down in the hierarchy, according to temporal constraints.In this paper we design and analyze time-bound hierarchical key assignment schemes which are provably-secure and efficient. We consider two different goals: security with respect to key indistinguishability and against key recovery. Moreover, we distinguish security against static and adaptive adversarial behaviors. We explore the relations between all possible combinations of security goals and adversarial behaviors and, in particular, we prove that security against adaptive adversaries is (polynomially) equivalent to security against static adversaries. Finally, we propose two different constructions for time-bound key assignment schemes. The first one is based on symmetric encryption schemes, whereas the second one makes use of bilinear maps. Both constructions support updates to the access hierarchy with local changes to the public information and without requiring any private information to be re-distributed.

Enforcing non-hierarchical access policies by hierarchical key assignment schemes

Without proposing a new key assignment scheme, this paper presents a graph translation procedure so that more complicated non-hierarchical access control policies can be enforced by existing hierarchical key assignment schemes.

New constructions for provably-secure time-bound hierarchical key assignment schemes

A time-bound hierarchical key assignment scheme is a method to assign time-dependent encryption keys to a set of classes in a partially ordered hierarchy, in such a way that each class in the hierarchy can compute the keys of all classes lower down in the hierarchy, according to temporal constraints. In this paper we propose new constructions for time-bound hierarchical key assignment schemes which are provably secure with respect to key indistinguishability. Our constructions use as a building block any provably-secure hierarchical key assignment scheme without temporal constraints and exhibit a tradeoff among the amount of private information held by each class, the amount of public data, the complexity of key derivation, and the computational assumption on which their security is based. Moreover, the proposed schemes support updates to the access hierarchy with local changes to public information and without requiring any private information to be re-distributed.