Global Identifier Research Articles

Privacy-Preserving Decentralized Functional Encryption for Inner Product

To support secure data mining and privacy-preserving computation, partial access and selective computation on encrypted data are desirable. Functional encryption (FE) is a new paradigm of public-key encryption and allows authorized users to compute specific functions on encrypted data without knowing the data. However, in some FE schemes, a trusted central authority (CA) is required to generate secret keys for users according to the description of functions. In this paper, to reduce trust on the CA and protect users' privacy, a privacy-preserving decentralised FE for inner product (PPDFEIP) scheme is proposed where multiple authorities co-exist and work independently without any interaction. Especially, to resist collusion attacks, all secret keys of the same user are tied to his/her global identifier (GID), but authorities cannot know any information of the GID even if they collaborate. We formalize the definition and security model of our PPFEIP scheme, and propose a concrete construction. Furthermore, the proposed scheme is implemented and evaluated. Finally, the security of our PPDFEIP scheme is reduced to well-known complexity assumptions. The novelty is to reduce trust on the CA, protect users' privacy and enable authorized users to compute inner product on encrypted data without compromising confidentiality.

A Novel User Collusion‐Resistant Decentralized Multi‐Authority Attribute‐Based Encryption Scheme Using the Deposit on a Blockchain

Recently, the concept of a decentralized data marketplace is getting much attention to exchange user data. Multi‐authority attribute‐based encryption (ABE), which can provide flexibility and user‐centric access control, is previously widely used in decentralized data sharing applications and also becoming a foundation to build decentralized data trading applications. It is known that users in a multi‐authority ABE system can collude by sharing their secret information for malicious purposes. To address this issue, the collusion‐resistant multi‐authority ABE model was introduced in which a unique global identifier (GID) is issued by the central authority (CA) to each user. Unfortunately, such approach cannot be used directly to build a decentralized data marketplace as (a) such intervention of the CA is directly against the main motivation of the decentralized trading platform and, mostly importantly, (b) the CA can exploit its full knowledge on users’ GID to launch various attacks against users. Motivated by these observations, this paper introduces a novel user collusion‐resistant decentralized multi‐authority ABE scheme for privacy preserving data trading systems. In the existing multi‐authority ABE systems, users utilize his/her GID that is solely assigned by the CA to generate his/her secret keys throughout the collaboration with authorities and a user can compute multi‐authority keys by combining the secret keys (stem from the same GID) in various ways. In the proposed system, the CA only has a partial knowledge of users’ GIDs, and thus, users’ privacy can be protected. On the other hand, we set the user’s own partial GID as a secret which can be used to withdraw his/her deposit to discourage any possible collusion among users.

Anonymous Electronic Health Record Sharing Scheme Based on Decentralized Hierarchical Attribute-Based Encryption in Cloud Environment

The rapid development of communication technologies, the network, advanced computing methods and wireless medical sensors gives rise to a modern medical system. In this system, large-scale electronic health records (EHRs) are often outsourced to be stored at the third parties, such as cloud service providers (CSPs). However, CSPs are not trustworthy, that is, serious security and privacy concerns about cloud service exist because it may expose the user's sensitive data to CSPs or unauthorized users in transmission, storage and sharing. To prevent the privacy disclosure of patients better and realize information sharing more effectively, this paper proposes an anonymous EHRs sharing scheme based on decentralized hierarchical attribute-based encryption (ABE). In the proposed scheme, (1) Multiple attribute authority (AA) ABE is leveraged to achieve fine-grained and scalable data access control and avoid bottleneck. Meanwhile, hierarchical access tree is used to encrypt multiple files in one operation, thereby saving calculation and storage load greatly. Moreover, the hidden access policy enhances user privacy protection. (2) The global identifier (GID) of a user is introduced to resist the collusion attack of users. Subsequently, an anonymous key generation mechanism is equipped to prevent multiple AAs from building a full profile using the user's GID. (3) To ensure the correctness and integrity of EHRs, users can conduct double verification based on the verification tag and convergent key. Finally, the efficiency analysis and experiments show that the scheme meets the security requirements of key management and privacy preservation in cloud and is proven secure and efficient in practice under the decisional bilinear Diffie-Hellman (DBDH) assumption.

A REVIEW PAPER ON ATTRIBUTE-BASED ENCRYPTION FOR MESSAGE PRIVACY IN CLOUD

The notion of attribute-based encryption (ABE)was proposed as an economical alternative to public-keyinfrastructures. It is the set of descriptive attributes, used as anidentity to generate a secret key, as well as serving as theaccess structure that performs access control. ABE is also auseful building block in various cryptographic primitives suchas searchable encryption. . It successfully integratesEncryption and Access Control and is ideal for sharing secretsamong groups, especially in a Cloud environment. Mostdeveloped ABE schemes support key-policy or ciphertextpolicyaccess control in addition to other features such asdecentralized authority, efficient revocation and keydelegation. This paper surveys mainstream papers, analyzesmain features for desired ABE systems, and classifies theminto different categories. With this high-level guidance, futureresearchers can treat these features as individual modules andselect related ones to build their ABE systems on demand.For ABE, it is not realistic to trust a single authority tomonitor all attributes and hence distributing control over manyattribute-authorities is desirable.A multi-authority ABE scheme can be realized with a trustedcentral authority (CA) which issues part of the decryption keyaccording to a user's global identifier (GID). However, this CAmay have the power to decrypt every cipher text, and the useof a consistent GID allowed the attribute-authorities tocollectively build user's attributes. Decentralized ABE schemecan eliminate the burden of heavy communication andcollaborative computation. It is observed that privacypreservingdecentralized key-policy ABE scheme has claimedto achieve better privacy for users and is provably secure inthe standard model

Constant Size Ciphertext Distributed CP-ABE Scheme With Privacy Protection and Fully Hiding Access Structure

In ciphertext-policy attribute-based encryption (CP-ABE) schemes, the computational overhead and the length for the ciphertext are positively correlated with the complexity of the access structure. In addition, the access structure embedded in ciphertext may be a leak sensitive information for the user. In order to solve the above issues, we provide a constant size ciphertext distributed CP-ABE scheme with privacy protection and fully hiding access policy (PPFH-CP-ABE) scheme. Our scheme can protect user's privacy from the following two aspects: 1) A user obtains private keys for his attributes from different authorities who get nothing about user's global identifier (GID) and attributes and 2) Access structure in the ciphertext is fully hidden. In addition, our scheme is able to resist the collusion attacks since the user's GID is nonlinearly bound to his private key from each authority. The presented scheme is proven CPA-secure in selective security model under the decisional DBDH assumption.

Security analysis of a privacy‐preserving decentralized ciphertext‐policy attribute‐based encryption scheme

SummaryAs it does not require a central authority or the cooperation among multiple authorities, decentralized attribute‐based encryption is an efficient and flexible multi‐authority attribute‐based encryption system. In most existing multi‐authority attribute‐based encryption schemes, a global identifier (GID) is introduced to act as the linchpin to resist collusion attacks. Because GID as well as some sensitive attributes used to apply for secret keys will lead to the compromise of user's privacy, some schemes towards solving these privacy issues have been proposed. Nevertheless, only the privacy of GID was considered in prior works. Recently in ESORICS 2014, Han et al. put forward a privacy‐preserving decentralized ciphertext‐policy attribute‐based encryption scheme in the standard model to address the additive privacy of attributes. In their work, a privacy‐preserving key extract protocol is presented to protect both user's identifier and attributes. In this paper, we point out the security weakness of the scheme of Han et al. We present a collusion attack on their basic decentralized ciphertext‐policy attribute‐based encryption scheme and additionally show that the privacy protection of attributes in their privacy‐preserving key extract protocol cannot be provided. Copyright © 2015 John Wiley & Sons, Ltd.

Message Privacy with Load Balancing using Attribute based Encryption

notion of attribute-based encryption (ABE) was proposed as an economical alternative to public-key infrastructures. ABE is also a useful building block in various cryptographic primitives such as searchable encryption. For ABE, it is not realistic to trust a single authority to monitor all attributes and hence distributing control over many attribute-authorities is desirable. A multi-authority ABE scheme can be realized with a trusted central authority (CA) which issues part of the decryption key according to a user's global identifier (GID). However, this CA may have the power to decrypt every cipher text, and the use of a consistent GID allowed the attribute-authorities to collectively build user's attributes. Decentralized ABE scheme can eliminate the burden of heavy communication and collaborative computation. It is observed that privacy-preserving decentralized key-policy ABE scheme has claimed to achieve better privacy for users and is provably secure in the standard model. However, after carefully revisiting the scheme, it is observed that existing system cannot resist the collusion attacks, hence fails to meet the basic security definitions of the ABE system. This paper proposes a solution without the trusted CA and without compromising users' privacy, thus making ABE more usable in practice. The privileged users are the users who will exactly match policy attributes with decentralized authority. To the best of our knowledge this framework of privileged users enhances the access control mechanism by avoiding the collusion. Collusion attack occurs when more than one user try to occupy same resource at a time. Proposed system resists collusion attack at every execution. After some encryption and decryption there can be load on the system. This load can be reduced using this system in terms of processing speed. When system load is increased backup server will be initialized to reduce system load and speedup the processing of cryptography. The message privacy is therefore enhanced with load balancing using attribute based encryption (LB-ABE), as it provides an added support of rebalancing which inherently supports optimally more user work-load.

Privacy-Preserving Decentralized Key-Policy Attribute-Based Encryption

Decentralized attribute-based encryption (ABE) is a variant of a multiauthority ABE scheme where each authority can issue secret keys to the user independently without any cooperation and a central authority. This is in contrast to the previous constructions, where multiple authorities must be online and setup the system interactively, which is impractical. Hence, it is clear that a decentralized ABE scheme eliminates the heavy communication cost and the need for collaborative computation in the setup stage. Furthermore, every authority can join or leave the system freely without the necessity of reinitializing the system. In contemporary multiauthority ABE schemes, a user's secret keys from different authorities must be tied to his global identifier (GID) to resist the collusion attack. However, this will compromise the user's privacy. Multiple authorities can collaborate to trace the user by his GID, collect his attributes, then impersonate him. Therefore, constructing a decentralized ABE scheme with privacy-preserving remains a challenging research problem. In this paper, we propose a privacy-preserving decentralized key-policy ABE scheme where each authority can issue secret keys to a user independently without knowing anything about his GID. Therefore, even if multiple authorities are corrupted, they cannot collect the user's attributes by tracing his GID. Notably, our scheme only requires standard complexity assumptions (e.g., decisional bilinear Diffie-Hellman) and does not require any cooperation between the multiple authorities, in contrast to the previous comparable scheme that requires nonstandard complexity assumptions (e.g., q-decisional Diffie-Hellman inversion) and interactions among multiple authorities. To the best of our knowledge, it is the first decentralized ABE scheme with privacy-preserving based on standard complexity assumptions.