Efficient Multi-Authority Attribute-Based Encryption with Policy Hiding and Updating

The emerging cloud-based Internet of Things (IoT) paradigm enables IoT devices to directly upload their collected data to the remote cloud and allows data owners (DOs) to conveniently manage those data through cloud APIs, which has greatly reduced infrastructure investment and data management cost in many IoT applications. Considering that the outsourced data are out of the physical control of DOs and the cloud server (CS) cannot always be fully trusted, how to securely delete the unneeded sensitive data stored in cloud to prevent potential data leakage issues is a big challenge. Most of the existing solutions only support coarse-grained deletion and rely on the participation of the CS, so their flexibility and practicability are seriously restricted. In this article, based on an enhanced policy-based puncturable encryption (P-PUN-ENC) primitive, we propose a secure and fine-grained self-controlled outsourced data deletion scheme in cloud-based IoT. The main contribution of our scheme is that it enables DOs to precisely and permanently delete their outsourced IoT-driven data in a policy-based way without relying on the CS. To achieve this, we subtly utilize the logical relationship between the puncture policy and access policy, and design a policy transform method to convert the puncture process based on the puncture policies into the update process of access policies. Then, we utilize a key delegation technique in attribute-based encryption (ABE) to complete the corresponding key update operations. Additionally, to address the issue of growing key storage and decryption cost in P-PUN-ENC, we propose the outsourced policy-based puncturable encryption (OP-PUN-ENC) primitive by combining the key and decryption outsource technique with P-PUN-ENC. Comprehensive comparisons show that our proposed scheme can better meet the data deletion requirements in cloud-based IoT, and formal security proof and extensive simulation results demonstrate the reliability and efficiency of the proposed scheme.

Attribute-based encryption (ABE) for cloud computing access control is reviewed in this article. A taxonomy and comprehensive assessment criteria of ABE are first proposed. In the taxonomy, ABE schemes are assorted into key-policy ABE (KP-ABE) schemes, ciphertext-policy ABE (CP-ABE) schemes, anti-quantum ABE schemes, and generic constructions. In accordance with cryptographically functional features, CP-ABE is further divided into nine subcategories with regard to basic functionality, revocation, accountability, policy hiding, policy updating, multi-authority, hierarchy, offline computation, and outsourced computation. In addition, a systematical methodology for discussing and comparing existing ABE schemes is proposed. For KP-ABE and each type of CP-ABE, the corresponding access control scenario is presented and explained by concrete examples. Specifically, the syntax of ABE is given followed by the adversarial model and security goals. ABE schemes are discussed according to the design strategies and special features and are compared in the light of the proposed assessment criteria with respect to security and performance. Compared to related state-of-the-art survey papers, this article not only provides a broader 12 categories of ABE schemes, but also makes a more comprehensive and holistic comparison. Finally, a number of open research challenges in ABE are pointed out.

Attribute-based encryption schemes with constant-size ciphertexts

Most data nowadays are stored in the cloud; therefore, cloud computing and its extension—fog computing—are the most in-demand services at the present time. Cloud and fog computing platforms are largely used by Internet of Things (IoT) applications where various mobile devices, end users, PCs, and smart objects are connected to each other via the internet. IoT applications are common in several application areas, such as healthcare, smart cities, industries, logistics, agriculture, and many more. Due to this, there is an increasing need for new security and privacy techniques, with attribute-based encryption (ABE) being the most effective among them. ABE provides fine-grained access control, enables secure storage of data on unreliable storage, and is flexible enough to be used in different systems. In this paper, we survey ABE schemes, their features, methodologies, benefits/drawbacks, attacks on ABE, and how ABE can be used with IoT and its applications. This survey reviews ABE models suitable for IoT platforms, taking into account the desired features and characteristics. We also discuss various performance indicators used for ABE and how they affect efficiency. Furthermore, some selected schemes are analyzed through simulation to compare their efficiency in terms of different performance indicators. As a result, we find that some schemes simultaneously perform well in one or two performance indicators, whereas none shines in all of them at once. The work will help researchers identify the characteristics of different ABE schemes quickly and recognize whether they are suitable for specific IoT applications. Future work that may be helpful for ABE is also discussed.

The information-centric Internet of things (IC-IoT) is different from the traditional Internet of things (IoT) in that the device-to-device pattern is generalized to a device-to-network pattern. Furthermore, in an IC-IoT environment, there is a demand for protecting the security of all data generated from IC-IoT devices. A cryptography scheme named attribute-based encryption (ABE) represents a smart method of providing the fine-grained access control that can sufficiently protect data security. The most attractive advantage of ABE is its expressive access policy, which makes the access control of data flexible and manageable. However, there is a serious problem caused by such an access policy; it incurs a greater ciphertext redundancy and computational overhead. This implies that the current ABE scheme is hard to implement in the thin client devices of IC-IoT. In this paper, we propose a universalized policy-compacting method via sharing public parts of the policy. Compared with the original policy, the compacted policy applies a more compact ciphertext and requires less computation, communication, and storage cost. However, the policy-compacting problem is proved to be a non-deterministic polynomial complete (NPC) problem. Thus, a greedy algorithm is provided to obtain an approximate minimum compacted policy scale. Finally, we propose a compact ciphertext-policy attribute-based encryption (CCP-ABE) scheme with the policy-compacting method. A security proof and performance evaluation show that the proposed CCP-ABE scheme provides a comprehensive performance improvement.

In recent years, attribute-based encryption (ABE) provides a new idea to help researchers solving the problem of data privacy protection in cloud. But there are two issues in traditional ABE, the first issue is that the attributes in the access structures will be sent to users in cleartext together with the ciphertext. So a attacker has the opportunity to obtain some of the private information from the plaintext access structure. And the other issue is the traditional ABE scheme cannot revoke the users' illegal keys in an efficient way. To handle both of the above challenges, we come up with a large universe ciphertext-policy ABE (CP-ABE) scheme which supports partially hidden access structures (PHAS) and highly efficient key revocation at the same time in this paper. What's more, unlike most previous schemes, first our access structure is based on the expressive linear secret sharing scheme (LSSS) which supports both AND and OR gates in access formulas and second our scheme is built from the prime-order bilinear pairing groups. The comparison with other relevant works presents that our scheme is more comprehensive and efficient. Finally we rigorously prove and analyze that our scheme is selectively indistinguishable secure under chosen plaintext attacks (IND-CPA) in the random oracle model (ROM) and our access structure is really anonymous against off-line dictionary attacks.

Federated diagnosis, a concept emerging in Internet of Things (IoT)-based e-health systems, addresses the interconnectivity challenges of medical resources across different regions. Furthermore, flexible access control is required, which allows users to modify the access policy for encrypted data in the cloud without revealing sensitive information. Current solutions rely on third parties for policy modification, incur high computational overheads during user revocation, and expose user attributes to plaintext access policies. To address these issues, this study introduces a blockchain-assisted revocable federated diagnostic ciphertext policy attribute-based encryption (RFD-CPABE) scheme that enables policy conversion and revocation, which allows users to convert attribute-based encryption ciphertext to inner product encryption ciphertext swiftly and facilitates fast revocation using binary trees. This scheme enhances privacy protection by separating attribute names from values, thus concealing sensitive information within the access policies. Moreover, to reduce the computational burden on trusted institutions, the workload is decentralized utilizing a blockchain to minimize the pressure on the central servers. The formal security proof demonstrates the resilience of the scheme against selective chosen-plaintext attacks, and the experimental analysis confirms its superior efficiency compared to existing solutions.

A lightweight attribute-based encryption scheme for the Internet of Things

In the cloud, for achieving access control and keeping data confidential, the data owners could adopt attribute-based encryption to encrypt the stored data. Users with limited computing power are however more likely to delegate the mask of the decryption task to the cloud servers to reduce the computing cost. As a result, attribute-based encryption with delegation emerges. Still, there are caveats and questions remaining in the previous relevant works. For instance, during the delegation, the cloud servers could tamper or replace the delegated ciphertext and respond a forged computing result with malicious intent. They may also cheat the eligible users by responding them that they are ineligible for the purpose of cost saving. Furthermore, during the encryption, the access policies may not be flexible enough as well. Since policy for general circuits enables to achieve the strongest form of access control, a construction for realizing circuit ciphertext-policy attribute-based hybrid encryption with verifiable delegation has been considered in our work. In such a system, combined with verifiable computation and encrypt-then-mac mechanism, the data confidentiality, the fine-grained access control and the correctness of the delegated computing results are well guaranteed at the same time. Besides, our scheme achieves security against chosen-plaintext attacks under the k-multilinear Decisional Diffie-Hellman assumption. Moreover, an extensive simulation campaign confirms the feasibility and efficiency of the proposed solution.

Key regeneration-free ciphertext-policy attribute-based encryption and its application

The NATO Object Level Protection (OLP) is an approach to Allied data protection that aims to protect individual information objects separately. OLP has an evolution stage which involves the direct use of cryptography in this context, called Cryptographic Access Control. Using next-generation public-key encryption techniques called attribute-based encryption (ABE), RBAC policies may be directly encoded into encrypted objects and their respective key material. While attractive in theory, there is only little research on the performance impact of using different ABE solutions to determine their applicability in variety of military situations, for example tactical setups and military evolution stages of Internet-of-Things. Additionally, many of the early ABE schemes are lacking in their security model. Later schemes remedy these models, but with an additional impact in performance. In this paper, we will investigate the performance impact of using ABE with real-life military policies in the OLP context, both with proposed basic security model (selective security) ABE and newer full security ABE schemes. The investigation is performed by experimenting with existing ABE software libraries, such as PBC and Charm. We present both relative and absolute measures of bandwidth and computational performance of two, OLP-compatible ABE schemes.

Combining several results that have been published in the last years, it is known that it is impossible to design simple and secure attribute-based encryption schemes that work in (classical) settings like the RSA or the pairing-free discrete logarithm ones. The purpose of this article is to broadcast this message through a wide (maybe non-cryptographic) audience, specially now that attribute-based encryption is considered as a useful tool to secure real systems like the Internet of Things. Today, only attribute-based encryption schemes that employ tools like bilinear pairings or lattices can provide some real (and provable) level of security. As an example of the fact that this message is still unknown for many people, we revisit a (maybe non exhaustive) list of articles proposing such insecure attribute-based encryption schemes: we recall which of these schemes have already been attacked and we describe attacks for the other ones.

Attribute-based encryption (ABE) is an advanced cryptographic tool and useful to build various types of access control systems. Toward the goal of making ABE more practical, we propose key-policy (KP) and ciphertext-policy (CP) ABE schemes, which first support unbounded sizes of attribute sets and policies with negation and multi-use of attributes, allow fast decryption, and are adaptively secure under a standard assumption, simultaneously. Our schemes are more expressive than previous schemes and efficient enough. To achieve the adaptive security along with the other properties, we refine the technique introduced by Kowalczyk and Wee (Eurocrypt’19) so that we can apply the technique more expressive ABE schemes. Furthermore, we also present a new proof technique that allows us to remove redundant elements used in their ABE schemes. We implement our schemes in 128-bit security level and present their benchmarks for an ordinary personal computer and smartphones. They show that all algorithms run in one second with the personal computer when they handle any policy or attribute set with one hundred attributes.

Disclosure of sensitive data leads to identity theft and violation of privacy. The untrusted cloud service provider (CSP) may try to disclose/misuse the data. It is necessary to provide access control and security over the outsourced and shared data to hide it from the CSP and unauthorized users. Traditional access control schemes are prone to security threats in the cloud environment. Attribute-based access control schemes (ABAC) are well suited for the cloud environment. Attribute-based encryption (ABE) is a promising cryptographic solution to provide fine-grained access control over the shared data. It selectively shares the data among the users and hides data from the CSP and unauthorized users. It preserves the privacy of users and the security of data being shared. Users can decrypt the data only if their attributes are satisfied with the access policy associated in the ciphertext. This paper presents a comprehensive survey of the ABE schemes. Taxonomy, performance comparison, and applications of ABE schemes are dealt with. The taxonomy and performance comparison help the selection of the most suitable ABE scheme based on specific usage scenarios. Thus, the survey opens up very interesting avenues for further research in this area, which are also discussed.

In multi‐authority attribute‐based encryption (ABE) systems, each authority manages a different attribute universe and issues the private keys to users. However, the previous multi‐authority ABE schemes are subject to such restrictions during initializing the systems: either the attribute universe is polynomially sized and the attributes have to be enumerated or the attribute universe can be exponentially large, but the size of the set of attributes, which will be used in encryption, is not more than a predefined fixed value. These restrictions prevent multi‐authority ABE schemes from being deployed in dynamic practice applications. In this paper, we present a large universe decentralized key‐policy ABE scheme without such additional limitation. In our scheme, there is no requirement of any central authority. Each attribute authority executes independently from the others and can join or depart the system allodiality. Our system supports any monotone access policy. The proposed scheme is constructed on prime order groups and proved selectively secure in the standard model. To the best of our knowledge, our scheme is the first large universe decentralized key‐policy ABE system in the standard model. Copyright © 2014 John Wiley & Sons, Ltd.