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 Construction of Server-Aided Revocable Hierarchical Identity-Based Encryption with Decryption Key Exposure Resistance

In this paper, we extend the notion of server-aided revocable identity-based encryption (SR-IBE) to the hierarchical IBE (HIBE) setting and propose a generic construction of server-aided revocable hierarchical IBE (SR-HIBE) schemes with decryption key exposure resistance (DKER) from any (weak) L-level revocable HIBE scheme without DKER and (L+1)-level HIBE scheme. In order to realize the server-aided revocation mechanism, we use the “double encryption” technique, and this makes our construction has short ciphertext size. Furthermore, when the maximum hierarchical depth is one, we obtain a generic construction of SR-IBE schemes with DKER from any IBE scheme and two-level HIBE scheme

Reuse It Or Lose It: More Efficient Secure Computation Through Reuse of Encrypted Values

Two-party secure function evaluation (SFE) has become significantly more feasible, even on resource-constrained devices, because of advances in server-aided computation systems. However, there are still bottlenecks, particularly in the input validation stage of a computation. Moreover, SFE research has not yet devoted sufficient attention to the important problem of retaining state after a computation has been performed so that expensive processing does not have to be repeated if a similar computation is done again. This paper presents PartialGC, an SFE system that allows the reuse of encrypted values generated during a garbled-circuit computation. We show that using PartialGC can reduce computation time by as much as 96% and bandwidth by as much as 98% in comparison with previous outsourcing schemes for secure computation. We demonstrate the feasibility of our approach with two sets of experiments, one in which the garbled circuit is evaluated on a mobile device and one in which it is evaluated on a server. We also use PartialGC to build a privacy-preserving "friend finder" application for Android. The reuse of previous inputs to allow stateful evaluation represents a new way of looking at SFE and further reduces computational barriers.Comment: 20 pages, shorter conference version published in Proceedings of the 2014 ACM SIGSAC Conference on Computer and Communications Security, Pages 582-596, ACM New York, NY, US

Denial-of-Service Resistance in Key Establishment

Denial of Service (DoS) attacks are an increasing problem for network connected systems. Key establishment protocols are applications that are particularly vulnerable to DoS attack as they are typically required to perform computationally expensive cryptographic operations in order to authenticate the protocol initiator and to generate the cryptographic keying material that will subsequently be used to secure the communications between initiator and responder. The goal of DoS resistance in key establishment protocols is to ensure that attackers cannot prevent a legitimate initiator and responder deriving cryptographic keys without expending resources beyond a responder-determined threshold. In this work we review the strategies and techniques used to improve resistance to DoS attacks. Three key establishment protocols implementing DoS resistance techniques are critically reviewed and the impact of misapplication of the techniques on DoS resistance is discussed. Recommendations on effectively applying resistance techniques to key establishment protocols are made

Security Enhanced Location-aided Level-based Disjoint Multipath Routing Algorithm for Mobile Ad Hoc Networks

In mobile ad hoc networks (MANET), the location-based multipath routing protocols involves less routing overhead compared to non-location-based protocols. This paper proposes two location-based algorithms, Enhanced Location-aided Level-based node Disjoint Multipath routing (ELLDMR) and Secure Location-aided Level-based node Disjoint Multipath routing (SLLDMR), to enhance the link lifetime and the security of the MANET. The objective of ELLDMR is to build multiple paths with non-critical nodes so that the lifetime of the routing path is significantly increased. It also hides the source, destination and path identity in intermediate nodes to avoid intrusion of routing attacks in the routing path. The SLLDMR is an enhancement over ELLDMR where it aims to overcome rushing attack and exhibit secure data transmission using two-level cryptographic processes. The performances of ELLDMR and SLLDMR are simulated using NS2 where it shows a minimum routing overhead, less end to end delay and high packet delivery compared to existing Location-aided Level-based node Disjoint Multipath routing (LLDMR) algorithm and Topology Hiding multipath protocol (TOHIP)

New Conditional Privacy-preserving Encryption Schemes in Communication Network

Nowadays the communication networks have acted as nearly the most important fundamental infrastructure in our human society. The basic service provided by the communication networks are like that provided by the ubiquitous public utilities. For example, the cable television network provides the distribution of information to its subscribers, which is much like the water or gas supply systems which distribute the commodities to citizens. The communication network also facilitates the development of many network-based applications such as industrial pipeline controlling in the industrial network, voice over long-term evolution (VoLTE) in the mobile network and mixture reality (MR) in the computer network, etc. Since the communication network plays such a vital role in almost every aspect of our life, undoubtedly, the information transmitted over it should be guarded properly. Roughly, such information can be categorized into either the communicated message or the sensitive information related to the users. Since we already got cryptographical tools, such as encryption schemes, to ensure the confidentiality of communicated messages, it is the sensitive personal information which should be paid special attentions to. Moreover, for the benefit of reducing the network burden in some instances, it may require that only communication information among legitimated users, such as streaming media service subscribers, can be stored and then relayed in the network. In this case, the network should be empowered with the capability to verify whether the transmitted message is exchanged between legitimated users without leaking the privacy of those users. Meanwhile, the intended receiver of a transmitted message should be able to identify the exact message sender for future communication. In order to cater to those requirements, we re-define a notion named conditional user privacy preservation. In this thesis, we investigate the problem how to preserve user conditional privacy in pubic key encryption schemes, which are used to secure the transmitted information in the communication networks. In fact, even the term conditional privacy preservation has appeared in existing works before, there still have great differences between our conditional privacy preservation definition and the one proposed before. For example, in our definition, we do not need a trusted third party (TTP) to help tracing the sender of a message. Besides, the verification of a given encrypted message can be done without any secret. In this thesis, we also introduce more desirable features to our redefined notion user conditional privacy preservation. In our second work, we consider not only the conditional privacy of the message sender but also that of the intended message receiver. This work presents a new encryption scheme which can be implemented in communication networks where there exists a blacklist containing a list of blocked communication channels, and each of them is established by a pair of sender and receiver. With this encryption scheme, a verifier can confirm whether one ciphertext is belonging to a legitimated communication channel without knowing the exact sender and receiver of that ciphertext. With our two previous works, for a given ciphertext, we ensure that no one except its intended receiver can identify the sender. However, the receiver of one message may behave dishonest when it tries to retrieve the real message sender, which incurs the problem that the receiver of a message might manipulate the origin of the message successfully for its own benefit. To tackle this problem, we present a novel encryption scheme in our third work. Apart from preserving user conditional privacy, this work also enforces the receiver to give a publicly verifiable proof so as to convince others that it is honest during the process of identifying the actual message sender. In our forth work, we show our special interest in the access control encryption, or ACE for short, and find this primitive can inherently achieve user conditional privacy preservation to some extent. we present a newly constructed ACE scheme in this work, and our scheme has advantages over existing ACE schemes in two aspects. Firstly, our ACE scheme is more reliable than existing ones since we utilize a distributed sanitizing algorithm and thus avoid the so called single point failure happened in ACE systems with only one sanitizer. Then, since the ciphertext and key size of our scheme is more compact than that of the existing ACE schemes, our scheme enjoys better scalability