Efficient Revocable Identity-Based Encryption via Subset Difference Methods

Providing an efficient revocation mechanism for identity-based encryption (IBE) is very important since a user\u27s credential (or private key) can be expired or revealed. Revocable IBE (RIBE) is an extension of IBE that provides an efficient revocation mechanism. Previous RIBE schemes essentially use the complete subtree (CS) scheme of Naor, Naor and Lotspiech (CRYPTO 2001) for key revocation. In this paper, we present a new technique for RIBE that uses the efficient subset difference (SD) scheme of Naor et al. instead of using the CS scheme to improve the size of update keys. Following our new technique, we first propose an efficient RIBE scheme in prime-order bilinear groups by combining the IBE scheme of Boneh and Boyen and the SD scheme and prove its selective security under the standard assumption. Our RIBE scheme is the first RIBE scheme in bilinear groups that has $O(r)$ number of group elements in an update key where $r$ is the number of revoked users. Next, we also propose another RIBE scheme in composite-order bilinear groups and prove its full security under static assumptions. Our RIBE schemes also can be integrated with the layered subset difference (LSD) scheme of Halevy and Shamir (CRYPTO 2002) to reduce the size of a private key

Server-Aided Revocable Predicate Encryption: Formalization and Lattice-Based Instantiation

Efficient user revocation is a necessary but challenging problem in many multi-user cryptosystems. Among known approaches, server-aided revocation yields a promising solution, because it allows to outsource the major workloads of system users to a computationally powerful third party, called the server, whose only requirement is to carry out the computations correctly. Such a revocation mechanism was considered in the settings of identity-based encryption and attribute-based encryption by Qin et al. (ESORICS 2015) and Cui et al. (ESORICS 2016), respectively. In this work, we consider the server-aided revocation mechanism in the more elaborate setting of predicate encryption (PE). The latter, introduced by Katz, Sahai, and Waters (EUROCRYPT 2008), provides fine-grained and role-based access to encrypted data and can be viewed as a generalization of identity-based and attribute-based encryption. Our contribution is two-fold. First, we formalize the model of server-aided revocable predicate encryption (SR-PE), with rigorous definitions and security notions. Our model can be seen as a non-trivial adaptation of Cui et al.'s work into the PE context. Second, we put forward a lattice-based instantiation of SR-PE. The scheme employs the PE scheme of Agrawal, Freeman and Vaikuntanathan (ASIACRYPT 2011) and the complete subtree method of Naor, Naor, and Lotspiech (CRYPTO 2001) as the two main ingredients, which work smoothly together thanks to a few additional techniques. Our scheme is proven secure in the standard model (in a selective manner), based on the hardness of the Learning With Errors (LWE) problem.Comment: 24 page

Generic Constructions of RIBE via Subset Difference Method

Revocable identity-based encryption (RIBE) is an extension of IBE which can support a key revocation mechanism, and it is important when deploying an IBE system in practice. Boneh and Franklin (Crypto\u2701) presented the first generic construction of RIBE, however, their scheme is not scalable where the size of key updates is linear in the number of users in the system. The first generic construction of RIBE is presented by Ma and Lin with complete subtree (CS) method by combining IBE and hierarchical IBE (HIBE) schemes. Recently, Lee proposed a new generic construction using the subset difference (SD) method by combining IBE,identity-based revocation (IBR), and two-level HIBE schemes. In this paper, we present a new primitive called Identity-Based Encryption with Ciphertext Delegation (CIBE) and propose a generic construction of RIBE scheme via subset difference method using CIBE and HIBE as building blocks. CIBE is a special type of Wildcarded IBE (WIBE) and Identity-Based Broadcast Encryption (IBBE). Furthermore, we show that CIBE can be constructed from IBE in a black-box way. Instantiating the underlying building blocks with different concrete schemes, we can obtain a RIBE scheme with constant-size public parameter, ciphertext, private key and $O(r)$ key updates in the selective-ID model. Additionally, our generic RIBE scheme can be easily converted to a sever-aided RIBE scheme which is more suitable for lightweight devices

A secure IoT cloud storage system with fine-grained access control and decryption key exposure resistance

Internet of Things (IoT) cloud provides a practical and scalable solution to accommodate the data management in large-scale IoT systems by migrating the data storage and management tasks to cloud service providers (CSPs). However, there also exist many data security and privacy issues that must be well addressed in order to allow the wide adoption of the approach. To protect data confidentiality, attribute-based cryptosystems have been proposed to provide fine-grained access control over encrypted data in IoT cloud. Unfortunately, the existing attributed-based solutions are still insufficient in addressing some challenging security problems, especially when dealing with compromised or leaked user secret keys due to different reasons. In this paper, we present a practical attribute-based access control system for IoT cloud by introducing an efficient revocable attribute-based encryption scheme that permits the data owner to efficiently manage the credentials of data users. Our proposed system can efficiently deal with both secret key revocation for corrupted users and accidental decryption key exposure for honest users. We analyze the security of our scheme with formal proofs, and demonstrate the high performance of the proposed system via experiments

A Generic Construction of Revocable Identity-Based Encryption

Revocable identity-based encryption (RIBE) is an extension of IBE that supports a key revocation mechanism, which is important when deployed an IBE system in practice. Boneh and Franklin presented the first generic construction of RIBE, however, their scheme is not scalable where the size of key update is linear in the number of users in the system. Then, Boldyreva, Goyal and Kumar presented the first scalable RIBE where the size of key update is logarithmic in the number of users and linear in the number of revoked users. In this paper, we present a generic construction of scalable RIBE from any IBE in a black-box way. Our construction has some merits both in theory and in practice. We obtain the first RIBE scheme based on quadratic residuosity problem and the first adaptively secure RIBE scheme based on lattices if we instantiate the underlying IBE with IBE schemes from quadratic residuosity assumption and adaptively secure IBE from lattices, respectively. In addition, the size of public parameters and secret keys are the same as that of the underlying IBE schemes. In server-aided model, the overheads of communication and computation for receivers are the same as those of underlying IBE schemes. Furthermore, the storage overhead for key update in our scheme is constant (in the number of users) while it was linear in the number of users in previous works

Attribute-based encryption for cloud computing access control: A survey

National Research Foundation (NRF) Singapore; AXA Research Fun

Secure data sharing in cloud and IoT by leveraging attribute-based encryption and blockchain

“Data sharing is very important to enable different types of cloud and IoT-based services. For example, organizations migrate their data to the cloud and share it with employees and customers in order to enjoy better fault-tolerance, high-availability, and scalability offered by the cloud. Wearable devices such as smart watch share user’s activity, location, and health data (e.g., heart rate, ECG) with the service provider for smart analytic. However, data can be sensitive, and the cloud and IoT service providers cannot be fully trusted with maintaining the security, privacy, and confidentiality of the data. Hence, new schemes and protocols are required to enable secure data sharing in the cloud and IoT. This work outlines our research contribution towards secure data sharing in the cloud and IoT. For secure data sharing in the cloud, this work proposes several novel attribute-based encryption schemes. The core contributions to this end are efficient revocation, prevention of collusion attacks, and multi-group support. On the other hand, for secure data sharing in IoT, a permissioned blockchain-based access control system has been proposed. The system can be used to enforce fine-grained access control on IoT data where the access control decision is made by the blockchain-based on the consensus of the participating nodes”--Abstract, page iv

Fully Collusion Resistant Trace-and-Revoke Functional Encryption for Arbitrary Identities

Functional Encryption (FE) has been extensively studied in the recent years, mainly focusing on the feasibility of constructing FE for general functionalities, as well as some realizations for restricted functionalities of practical interest, such as inner-product. However, little consideration has been given to the issue of key leakage on FE. The property of FE that allows multiple users to obtain the same functional keys from the holder of the master secret key raises an important problem: if some users leak their keys or collude to create a pirated decoder, how can we identify at least one of those users, given some information about the compromised keys or the pirated decoder? Moreover, how do we disable the decryption capabilities of those users (i.e. traitors)? Two recent works have offered potential solutions to the above traitor scenario. However, the two solutions satisfy weaker notions of security and traceability, can only tolerate bounded collusions (i.e., there is an a priori bound on the number of keys the pirated decoder obtains), or can only handle a polynomially large universe of possible identities. In this paper, we study trace-and-revoke mechanism on FE and provide the first construction of trace-and-revoke FE that supports arbitrary identities, is both fully collusion resistant and fully anonymous. Our construction relies on a generic transformation from revocable predicate functional encryption with broadcast (RPFE with broadcast, which is an extension of revocable predicate encryption with broadcast proposed by Kim and J. Wu at ASIACRYPT\u272020) to trace-and-revoke FE. Since this construction admits a generic construction of trace-and-revoke inner-product FE (IPFE), we instantiate the trace-and-revoke IPFE from the well-studied Learning with Errors (LWE). This is achieved by proposing a new LWE-based attribute-based IPFE (ABIPFE) scheme to instantiate RPFE with broadcast