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

Group signature revocable anonymity scheme for network monitoring

Subscriber’s Privacy is in a constant conflict with security and accountability providing controls employed for network monitoring activities of service providers and enterprises. This paper presents the results of the author’s research in the field of distributed network security monitoring architectures and the proposal of such a system that incorporates cryptographic protocols and a group signature scheme to deliver privacy protecting, network surveillance system architecture that provides subscriber’s accountability and controlled, revocable anonymity

A new revocable and re-delegable proxy signature and its application

With the popularity of cloud computing and mobile Apps, on-demand services such as on-line music or audio streaming and vehicle booking are widely available nowadays. In order to allow efficient delivery and management of the services, for large-scale on-demand systems, there is usually a hierarchy where the service provider can delegate its service to a top-tier (e.g., countrywide) proxy who can then further delegate the service to lower level (e.g., region-wide) proxies. Secure (re-)delegation and revocation are among the most crucial factors for such systems. In this paper, we investigate the practical solutions for achieving re-delegation and revocation utilizing proxy signature. Although proxy signature has been extensively studied in the literature, no previous solution can achieve both properties. To fill the gap, we introduce the notion of revocable and re-delegable proxy signature that supports efficient revocation and allows a proxy signer to re-delegate its signing right to other proxy signers without the interaction with the original signer. We define the formal security models for this new primitive and present an efficient scheme that can achieve all the security properties. We also present a secure on-line revocable and re-delegate vehicle ordering system (RRVOS) as one of the applications of our proposed scheme

Anonymous and Adaptively Secure Revocable IBE with Constant Size Public Parameters

In Identity-Based Encryption (IBE) systems, key revocation is non-trivial. This is because a user's identity is itself a public key. Moreover, the private key corresponding to the identity needs to be obtained from a trusted key authority through an authenticated and secrecy protected channel. So far, there exist only a very small number of revocable IBE (RIBE) schemes that support non-interactive key revocation, in the sense that the user is not required to interact with the key authority or some kind of trusted hardware to renew her private key without changing her public key (or identity). These schemes are either proven to be only selectively secure or have public parameters which grow linearly in a given security parameter. In this paper, we present two constructions of non-interactive RIBE that satisfy all the following three attractive properties: (i) proven to be adaptively secure under the Symmetric External Diffie-Hellman (SXDH) and the Decisional Linear (DLIN) assumptions; (ii) have constant-size public parameters; and (iii) preserve the anonymity of ciphertexts---a property that has not yet been achieved in all the current schemes

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

SEA-BREW: A scalable Attribute-Based Encryption revocable scheme for low-bitrate IoT wireless networks

Attribute-Based Encryption (ABE) is an emerging cryptographic technique that allows one to embed a fine-grained access control mechanism into encrypted data. In this paper we propose a novel ABE scheme called SEA-BREW (Scalable and Efficient Abe with Broadcast REvocation for Wireless networks), which is suited for Internet of Things (IoT) and Industrial IoT (IIoT) applications. In contrast to state-of-the-art ABE schemes, ours is capable of securely performing key revocations with a single short broadcast message, instead of a number of unicast messages that is linear with the number of nodes. This is desirable for low-bitrate Wireless Sensor and Actuator Networks (WSANs) which often are the heart of (I)IoT systems. In SEA-BREW, sensors, actuators, and users can exchange encrypted data via a cloud server, or directly via wireless if they belong to the same WSAN. We formally prove that our scheme is secure also in case of an untrusted cloud server that colludes with a set of users, under the generic bilinear group model. We show by simulations that our scheme requires a constant computational overhead on the cloud server with respect to the complexity of the access control policies. This is in contrast to state-of-the-art solutions, which require instead a linear computational overhead

A Revocable Group Signature Scheme with Scalability from Simple Assumptions and Its Application to Identity Management

Group signatures are signatures providing signer anonymity where signers can produce signatures on behalf of the group that they belong to. Although such anonymity is quite attractive considering privacy issues, it is not trivial to check whether a signer has been revoked or not. Thus, how to revoke the rights of signers is one of the major topics in the research on group signatures. In particular, scalability, where the signing and verification costs and the signature size are constant in terms of the number of signers N, and other costs regarding signers are at most logarithmic in N, is quite important. In this paper, we propose a revocable group signature scheme which is currently more efficient compared to previous all scalable schemes. Moreover, our revocable group signature scheme is secure under simple assumptions (in the random oracle model), whereas all scalable schemes are secure under q-type assumptions. We implemented our scheme by employing Barreto-Lynn-Scott curves of embedding degree 12 over a 455-bit prime field (BLS-12-455), and Barreto-Naehrig curves of embedding degree 12 over a 382-bit prime field (BN-12-382), respectively, by using the RELIC library. We showed that the online running times of our signing algorithm were approximately 14 msec (BLS-12-455) and 11 msec (BN-12-382), and those of our verification algorithm were approximately 20 msec (BLS-12-455) and 16 msec (BN-12-382), respectively. Finally, we showed that our scheme is applied to an identity management system proposed by Isshiki et al

Contributions to Identity-Based Broadcast Encryption and Its Anonymity

Broadcast encryption was introduced to improve the efficiency of encryption when a message should be sent to or shared with a group of users. Only the legitimate users chosen in the encryption phase are able to retrieve the message. The primary challenge in construction a broadcast encryption scheme is to achieve collusion resistance such that the unchosen users learn nothing about the content of the encrypted message even they collude

One-time and Revocable Ring Signature with Logarithmic Size in Blockchain

Ring signature (RS) allows users to demonstrate to verifiers their membership within a specified group (ring) without disclosing their identities. Based on this, RS can be used as a privacy protection technology for users\u27 identities in blockchain. However, there is currently a lack of RS schemes that are fully applicable to the blockchain applications: Firstly, users can only spend a UTXO once, and the current RS schemes are not yet perfect in a one-time manner. At the same time, the current RS schemes are not sufficiently developed in terms of regulation. Secondly, the size of the current RS is mostly linearly related to the number of ring members. When there are many members, the transaction processing speed is slow. We propose a one-time and revocable ring signature with logarithmic size in blockchain based on the Sigma-Protocols. Our scheme compresses the RS size and enables users to sign in the blockchain transactions. The scheme allows two RS generated with the same private key for a same UTXO to be linked together. Additionally, it allows regulatory authority to recover the signer\u27s identity at any time. A security model was presented, and its security properties, namely, unforgeability, anonymity, one-time, revocability, and non-slanderability were proven in the random oracle model. Our scheme compresses the RS size to where is the number of ring users, enabling blockchain transactions to have better processing speeds. And it can prevent double-spending attacks in blockchain and allows regulatory authority to recover the identity of the signer