Multi-authority proxy re-encryption based on CPABE for cloud storage systems

The mode of outsourcing brings about new challenges for data security and access control in cloud computing. Ciphertext-Policy Attribute-based Encryption (CP-ABE) is considered to be a powerful tool for protecting data confidentiality in cloud storage system. Due to the large scale of cloud, there are many independent domains. It is impossible for a single authority to issue attributes to all of the users. In addition, single authority could be the bottleneck of system. Attribute revocation has always been the primary difficulty in ABE. In this paper, we propose a multi-authority cloud access scheme with mixed access structure to support universal attribute and more flexible access control in multi-authority cloud storage system. After adding owner-defined attribute to traditional access structure, owner can decide which user has the right to access data. Two kinds of revocation methods can provide real-time privilege updating in multi-authority system. Detailed security analysis shows that the proposed MMACS scheme meets the security requirements under existing security models. Performance evaluation also demonstrates its highly efficient in attribute revocation.

Nowadays, many organizations are adopting cloud computing for storing the large amount of organization’s important and private data. Here, it becomes important to mange appropriate access rights to these data as it is stored outside the organization’s boundary and is handled by the third party service providers. The Ciphertext Policy Attribute-based Encryption (CPABE) scheme is the most widely utilized technique that offers encrypted access control. In the existing implementations of CPABE scheme, one of the significant issues that need to be addressed is an efficient revocation mechanism. In this paper a direct and immediate user revocation approach for CPABE scheme is presented. The proposed method offers direct user revocation by maintaining the revocation list and to keep revocation list smaller the validity time is embedded in the user’s secret key. The revoked users are still able to access the previously generated ciphertexts. Hence, ciphertext update process is incorporated and a separate immediate revocation list is maintained so that the revoked users’ access is restricted. Also, in the proposed system the revocation information is embedded in ciphertext as a separate part so the update process of ciphertext is more efficient.KeywordsAttributesRevocationABECPABERevocation listValidity periodCloudAccess structure

Cipher text-Policy Attribute Based Encryption (CP-ABE) is a promising cryptographic primitive for fine-grained access control of shared data. However, when CP-ABE is used to control outsourced data sharing, it confronts two obstacles. Firstly, the data owner must trust the attributes authority, secondly, the issue of attribute revocation of CP-ABE schemes, which suffers from such problems as different granularities of revocation, poor scalability and high computational complexity, is cumbersome. In this paper, we propose a new CP-ABE scheme that the data owners can fully control their outsourced shared data. We also resolve the issue of revocation including the entire user access privilege and just partial access right of the user, i.e., a subset of his/her attributes. Our proposed solution can achieve minimal overload by integrating CP-ABE with the access control of system. In addition, the data owners and the attributes authority can delegate most of laborious tasks to revocation proxy severs with the technique of proxy re-encryption. Finally, we present the quantitative test and analysis on the performance of our proposed scheme.

Data access control is an effective way to ensure the data security in the cloud. Due to data outsourcing and untrusted cloud servers, the data access control becomes a challenging issue in cloud storage systems. Ciphertext-Policy Attribute-based Encryption (CP-ABE) is regarded as one of the most suitable technologies for data access control in cloud storage, because it gives data owners more direct control on access policies. However, it is difficult to directly apply existing CP-ABE schemes to data access control for cloud storage systems because of the attribute revocation problem. In this paper, we design an expressive, efficient and revocable data access control scheme for multi-authority cloud storage systems, where there are multiple authorities co-exist and each authority is able to issue attributes independently. Specifically, we propose a revocable multi-authority CP-ABE scheme, and apply it as the underlying techniques to design the data access control scheme. Our attribute revocation method can efficiently achieve both forward security and backward security. The analysis and simulation results show that our proposed data access control scheme is secure in the random oracle model and is more efficient than previous works.

Hierarchical attribute-based encryption and scalable user revocation for sharing data in cloud servers

A Ciphertext-Policy Attribute-Based Encryption (CP-ABE) system extracts the decryption keys over attributes shared by multiple users. It brings plenty of advantages in ABE applications. CP-ABE enables fine-grained access control to the encrypted data for commercial applications. There has been significant progress in CP-ABE over the recent years because of two properties called traceability and large universe, greatly enriching the commercial applications of CP-ABE. Traceability is the ability of ABE to track the malicious users or traitors who intentionally leak the partial or modified decryption keys to others for profits. Nevertheless, due to the nature of CP-ABE, it is difficult to identify the original key owner from an exposed key since the decryption privilege is shared by multiple users who have the same attributes. On the other hand, the property of large universe in ABE proposed by Lewko and Waters enlarges the practical applications by supporting flexible number of attributes. Several systems have been proposed to obtain either of the above properties. However, none of them achieve the two properties simultaneously in practice, which limits the commercial applications of CP-ABE to a certain extent. In this paper, we propose a practical large universe CP-ABE system supporting white-box traceability, which is suitable for commercial applications. Compared to existing systems, our new system has three advantages: (1) The number of attributes is not polynomially bounded; (2) Malicious users who leak their decryption keys could be traced; and, (3) The storage overhead for traitor tracing is constant. We also prove the selective security of our new system in the standard model under “q-type” assumption.

In recent years, with the widely used of cloud computing, the security of network for data is more and more important. Traditional symmetric encryption requires both parties to hold the same encryption and decryption keys, which is not suitable for cloud computing environment. Asymmetric encryption also requires that each user and the system have an unique public-private key pair, making the key generation and holding costs are too high. So Ciphertext Policy Attribute-Based Encryption scheme comes in handy. After the attribute mechanism generates a public key and a master private key, it only needs to assign a set of private keys according to the attributes for each user, reducing the cost of key pairs. However, with the increase of user data, it takes more and more time for the data owner to encrypt data. How to accelerate the encryption speed also becomes the key to optimize the system. Combined with relevant research, this paper proposes an encryption scheme based on the multiplexing sub-strategy. On the basis of ensuring the original security, it optimizes the speed of multiple encryption schemes with the same sub-strategy that need to be encrypted simultaneously for the data owner, which greatly improves the computing speed.

Designing lightweight security protocols for cloud-based Internet-of-Things (IoT) applications for battery-limited mobile devices, such as smart phones and laptops, is a topic of recent focus. Ciphertext-policy attribute-based encryption (CP-ABE) is a viable solution, particularly for cloud deployment, as an encryptor can “write” the access policy so that only authorized users can decrypt and have access to the data. However, most existing CP-ABE schemes are based on the costly bilinear maps, and require long decryption keys, ciphertexts and incur significant computation costs in the encryption and decryption (e.g. costs is at least linear to the number of attributes involved in the access policy). These design drawbacks prevent the deployment of CP-ABE schemes on battery-limited mobile devices. In this paper, we propose a new RSA-based CP-ABE scheme with constant size secret keys and ciphertexts (CSKC) and has $\mathcal {O}(1)$ time-complexity for each decryption and encryption. Our scheme is then shown to be secure against a chosen-ciphertext adversary, as well as been an efficient solution with the expressive AND gate access structures (in comparison to other related existing schemes). Thus, the proposed scheme is suitable for deployment on battery-limited mobile devices.

In a Decentralized Identifier (DID), the Holder does not depend on a third party but controls self-identity information and is authenticated by the Verifier. Therefore, the Verifier can request verification data for access control from the Verifiable Data Registry (VDR) and credentials to authenticate the Holder. Data access control should be used when requesting data access such that only authorized Verifiers can access it. Consequently, studies on secure and efficient data access control have been conducted, and among them a scheme using Ciphertext Policy Attribute-based Encryption (CP-ABE) is underway. However, when the CP-ABE scheme is applied to the DID, the Holder’s extended Self-Sovereign Identity (SSI), which proves that the Holder has approved access to the Holder’s data stored in the VDR, is not ensured. Furthermore, the VDR does not verify the Verifier’s data access rights, resulting in unauthorized verification and illegal access to data by the user. And issue infringement of the Holder’s privacy, where Verifiers can infer the Holder by sharing and connecting the same DID-based Verifiable Presentations (VPs) of the Holder. Also, it leads to overheads in the amount of computation and search time for encryption/decryption. Therefore, in this paper, we propose a data access control for secure authentication by solving the security vulnerabilities of CP-ABE and using a CP-ABE-based dual Verifiable Credential (VC) scheme in DID.

This paper presents an architecture (RESCUE) of a system that is capable of implementing: a keyless encryption method, self-destruction of data within a time frame without user's intervention, and break-glass data recovery, with in-built failover protection. It aims to overcome many of the current problems within Cloud-based infastructures, such as in the loss of private keys, and inherent failover protection. The architecture uses a secret share method with: an Application Platform, Proxy Servers with Routers, and a Metadata Server. These interact within a multi-cloud environment to provide a robust, secure and dependable system, and which showcases a new direction in an improved cloud computing environment. It aims to ensure user privacy, and reduces the potential for data loss, as well as reducing denial-of-service outages within the cloud, and with failover protection for stored data. In order to assessement the best secret sharing method that could be used for the architecture, the paper outlines a range of experiments on the performance footprint of the most relevant secret sharing schemes.

Cryptographic cloud storage (CCS) is a secure architecture built in the upper layer of a public cloud infrastructure. In the CCS system, a user can define and manage the access control of the data by himself without the help of cloud storage service provider. The ciphertext-policy attribute-based encryption (CP-ABE) is considered as the critical technology to implement such access control. However, there still exists a large security obstacle to the implementation of CP-ABE in CCS. That is, how to identify the malicious cloud user who illegally shares his private keys with others or applies his keys to construct a decryption device/black-box, and provides the decryption service. Although several CP-ABE schemes with black-box traceability have been proposed to address the problem, most of them are not practical in CCS systems, due to the absence of scalability and expensive computation cost, especially the cost of tracing. Thus, we present a new black-box traceable CP-ABE scheme that is scalable and high efficient. To achieve a much better performance, our work is designed on the prime order bilinear groups that results in a great improvement in the efficiency of group operations, and the cost of tracing is reduced greatly to O ( N ) or O ( 1 ) , where N is the number of users of a system. Furthermore, our scheme is proved secure in a selective standard model. To the best of our knowledge, this work is the first such practical and provably secure CP-ABE scheme for CCS, which is black-box traceable.

Today a large volume of data is stored in cloud that requires fine grained accessibility for heterogeneous users. Cipher-text policy attribute based encryption (CP-ABE) has evolved into a promising solution for secure data storage with fine grained access control. In CP-ABE, the ciphertext is associated with an access policy (set of rules) and users can access the data if their attributes satisfies the access policy. However, existing CP-ABE schemes fail to perform in presence of large number of users and hierarchical relationships among them. Moreover, a majority of the CP-ABE schemes require large computational overhead for light weight applications. In this paper, we present a hierarchical attribute based cryptosystem by introducing hierarchical dependency between the users and thereby achieving multi-layer verification for fine grained data access. Moreover, our proposed cryptosystem is seamless to user revocation. The efficiency and security of our proposed cryptosystem have been analyzed and reported. Further we implement the proposed cryptosystem in Charm to demonstrate its practicality.

Secure cloud storage, which is an emerging cloud service, is designed to protect the confidentiality of outsourced data but also to provide flexible data access for cloud users whose data is out of physical control. Ciphertext-Policy Attribute-Based Encryption (CP-ABE) is regarded as one of the most promising techniques that may be leveraged to secure the guarantee of the service. However, the use of CP-ABE may yield an inevitable security breach which is known as the misuse of access credential (i.e., decryption rights), due to the intrinsic “all-or-nothing” decryption feature of CP-ABE. In this paper, we investigate the two main cases of access credential misuse: one is on the semi-trusted authority side, and the other is on the side of cloud user. To mitigate the misuse, we propose the first accountable authority and revocable CP-ABE based cloud storage system with white-box traceability and auditing, referred to as CryptCloud±. We also present the security analysis and further demonstrate the utility of our system via experiments.

A lightweight key management scheme for key-escrow-free ECC-based CP-ABE for IoT healthcare systems

Since cloud computing and other data outsourcing settings offer high flexibility and accessibility, many healthcare providers se personal health records (PHRs) that are electronic to let patients manage their own health data in a scalable and robust environment. However, PHRs contain extremely sensitive data, thus security and privacy issues are crucial. PHR owners should be free to create their own flexible and safe access rules for their data that is outsourced. Beyond the fundamental authentication feature, most commercial cloud platforms offer tenants the option of symmetric or public key encryption to protect their data. But because symmetric encryption has a large key management overhead and requires a lot of upkeep, In this study, we develop a fine-grained, secure access control system for outsourced PHRs that incorporates updates to the policies in a lightweight manner. Our suggested solution (PRE) is based on proxy re-encryption and ciphertext policy attribute-based encryption (CP-ABE). To assist complete policy change tracing, we also offer a policy versioning approach. Ultimately, an assessment of performance was carried out to demonstrate the efficacy of the suggested approach.