Multi-user Setting Research Articles

Attribute-based multi-user collaborative searchable encryption in COVID-19

With the outbreak of COVID-19, the government has been forced to collect a large amount of detailed information about patients in order to effectively curb the epidemic of the disease, including private data of patients. Searchable encryption is an essential technology for ciphertext retrieval in cloud computing environments, and many searchable encryption schemes are based on attributes to control user‘s search permissions to protect their data privacy. The existing attribute-based searchable encryption (ABSE) scheme can only implement the situation where the search permission of one person meets the search policy and does not support users to obtain the search permission through collaboration. In this paper, we proposed a new attribute-based collaborative searchable encryption scheme in multi-user setting (ABCSE-MU), which takes the access tree as the access policy and introduces the translation nodes to implement collaborative search. The cooperation can only be reached on the translation node and the flexibility of search permission is achieved on the premise of data security. ABCSE-MU scheme solves the problem that a single user has insufficient search permissions but still needs to search, making the user’s access policy more flexible. We use random blinding to ensure the confidentiality and security of the secret key, further prove that our scheme is secure under the Decisional Bilinear Diffie–Hellman (DBDH) assumption. Security analysis further shows that the scheme can ensure the confidentiality of data under chosen-keyword attacks and resist collusion attacks.

Multicarrier Acoustic Communications in Multiuser and Interference-Limited Regimes

In this article, we address the design of a multicarrier communication system based on orthogonal frequency-division multiplexing and direct sequence spread spectrum. The design targets operation in the low-signal-to-noise-ratio regimes and multiuser settings. Specifically, coding is employed across carriers such that channel estimation and signal detection are coupled. We consider both coherent and differentially coherent detection and extend the principles to multichannel reception. A custom-designed frequency synchronization technique is proposed to counteract the motion-induced Doppler frequency shifting effect. Using the recordings from the 2010 Mobile Acoustic Communication Experiment, where signals were transmitted in the 10.5–15.5-kHz acoustic band in shallow water, with relative motion up to 1.5 m/s, we demonstrate the system performance in terms of the mean squared error and bit error rate in data detection. Further employing Polar and low-density parity-check coding, we show that the proposed methods provide excellent performance while maintaining low computational complexity, making them suitable for a practical implementation.

Enabling Traceable and Verifiable Multi-User Forward Secure Searchable Encryption in Hybrid Cloud

Forward secure searchable encryption (FSSE) scheme allows one data user to search on encrypted databases while resisting the file injection attack. The data utilization can be further improved by extending the single-user scenario to the multi-user scenario. However, there are some issues needed to be considered when a data owner shares data with multiple data users. First, the public cloud server can not be completely trusted as it may be dishonest returning incorrect or incomplete results. Second, authorized users may trade their private keys for financial benefit. To our knowledge, state-of-the-art searchable encryption schemes only consider part of the following desirable features: the verifiability of results, the resistance to file injection attacks, the traceability and revocation of malicious users who abuse their private keys in the multi-user setting. Based on these motivations, we first propose enabling traceable and verifiable multi-user FSSE, which achieves the above functionalities. Besides, we carry out the security proof which demonstrates that our scheme can meet the requirements of security. We also assess the performance from theoretical analysis and experimental analysis, which shows that compared with other similar schemes, our scheme has richer functionalities with comparable efficiency.

Tight Multi-User Security Bound of DbHtS

In CRYPTO’21, Shen et al. proved that Two-Keyed-DbHtS construction is secure up to 22n/3 queries in the multi-user setting independent of the number of users. Here the underlying double-block hash function H of the construction realized as the concatenation of two independent n-bit keyed hash functions (HKh,1,HKh,2), and the security holds under the assumption that each of the n-bit keyed hash function is universal and regular. The authors have also demonstrated the applicability of their result to the key-reduced variants of DbHtS MACs, including 2K-SUM-ECBC, 2K-PMAC_Plus and 2K-LightMAC_Plus without requiring domain separation technique and proved 2n/3-bit multi-user security of these constructions in the ideal cipher model. Recently, Guo and Wang have invalidated the security claim of Shen et al.’s result by exhibiting three constructions, which are instantiations of the Two-Keyed-DbHtS framework, such that each of their n-bit keyed hash functions are O(2−n) universal and regular, while the constructions themselves are secure only up to the birthday bound. In this work, we show a sufficient condition on the underlying Double-block Hash (DbH) function, under which we prove an improved 3n/4-bit multi-user security of the Two-Keyed-DbHtS construction in the ideal-cipher model. To be more precise, we show that if each of the n-bit keyed hash function is universal, regular, and cross-collision resistant then it achieves the desired security. As an instantiation, we show that two-keyed Polyhash-based DbHtS construction is multi-user secure up to 23n/4 queries in the ideal-cipher model. Furthermore, due to the generic attack on DbHtS constructions by Leurent et al. in CRYPTO’18, our derived bound for the construction is tight.

MU-TEIR: Traceable Encrypted Image Retrieval in the Multi-User Setting

The encrypted image retrieval technique allows users to retrieve images in an encrypted manner without decrypting images. However, most of the existing schemes still are vulnerable to security threats and inefficiency, caused by malicious users and inefficient feature extraction methods, respectively. To this end, we propose a traceable encrypted image retrieval in the multi-user setting in this article, termed as MU-TEIR. First, MU-TEIR employs a convolutional neural network VGG16 to extract image feature vectors and calculate the mean and variance of the feature vectors to construct the index, then encrypts index with the distributed two trapdoors public-key cryptosystem. After that, MU-TEIR protects image content by encrypting each image pixel with a standard stream cipher. Furthermore, MU-TEIR utilizes a watermark-based mechanism to prevent malicious query users from maliciously distributing images. Detailed security analysis shows that MU-TEIR protects the outsourced images and indexes security as well as query privacy, and can track malicious users. Experimental results verify effectiveness of MU-TEIR.

Linear Algebraic Approach to Strongly Secure Ramp Secret Sharing for General Access Structures with Application to Symmetric PIR

Ramp secret sharing is a variant of secret sharing which can achieve better information ratio than perfect schemes by allowing some partial information on a secret to leak out. Strongly secure ramp schemes can control the amount of leaked information on the components of a secret. In this paper, we reduce the construction of strongly secure ramp secret sharing for general access structures to a linear algebraic problem. As a result, we show that previous results on strongly secure network coding imply two linear transformation methods to make a given linear ramp scheme strongly secure. They are explicit or provide a deterministic algorithm while the previous methods which work for any linear ramp scheme are non-constructive. In addition, we present a novel application of strongly secure ramp schemes to symmetric PIR in a multi-user setting. Our solution is advantageous over those based on a non-strongly secure scheme in that it reduces the amount of communication between users and servers and also the amount of correlated randomness that servers generate in the setup.

Streaming Erasure Codes Over Multi-Access Relayed Networks

Many emerging multimedia streaming applications involve multiple users communicating under strict latency constraints. In this paper we study streaming codes for a network involving two source nodes, one relay node and a destination node. In this paper’s setting, each source node transmits a stream of messages, through the relay, to a destination, who is required to decode the messages under a strict delay constraint. For the case of a single source node, a class of streaming codes has been proposed by Fong et al., using the concept of delay-spectrum. The current paper presents a novel framework, which constructs streaming codes for a relayed multi-user setting by sequentially constructing the codes for each link. This requires a characterization of the set of all achievable delay spectra for a given rate, blocklength and number of erasures, beyond the specific choice considered by Fong et al. This characterization is presented in the paper for systematic codes. Using this novel framework, the first proposed scheme involves greedily selecting the rate on the link from relay to destination and using properties of the delay-spectrum to find feasible streaming codes that satisfy the required delay constraints. A closed form expression for the achievable rate region is provided, and conditions for when the proposed scheme is optimal are established by a natural outer bound. The second proposed scheme builds upon this approach, but uses a numerical optimization-based approach to improve the achievable rate region over the first scheme. Experimental results show that the proposed schemes achieve significant improvements over baseline schemes based on single-user codes.

Toward Full-Immersive Multiuser Virtual Reality With Redirected Walking

We are witnessing a surge in the popularity and mass-availability of Virtual Reality (VR) technology. Toward enhancing its maturity, current research is focusing on achieving continuous full immersiveness of the VR users during their experiences in Virtual Environments (VEs), as well as on enabling multiuser experiences. In many cases, achieving the full immersiveness requires enabling the users’ perception of walking naturally in unbound VEs. Redirected Walking (RDW) algorithms provide a solution to this problem by exploiting the limitations of the human spatial perception. In other words, the RDW algorithms are envisioned to unnoticeably steer the VR users for constraining them within a certain tracking space. Regardless of notable research efforts targeting RDW, there are still not many experimental evaluations of the performance of RDW algorithms, especially in multiuser settings and utilizing contemporary Head-Mounted Devices (HMDs). Toward addressing this issue, we have developed a modular framework that enables straightforward experimentation with single and multiuser RDW in different tracking spaces and for varying VEs. The capabilities of the developed framework were demonstrated by carrying out an extensive experimentation study to capture the performance and noticeability of a contemporary RDW algorithm for a varying number of users in different tracking spaces and VEs. The lessons learned during the study have been conceptualized in a form of a set of RDW design enhancements that can be generically applied to existing RDW algorithms. We show that the proposed enhancements significantly increase the overall performance of RDW and decrease the noticeability of RDW-supported experiences in VEs.

Identity-based ring signature scheme with multi-designated verifiers

As far as we know, there is only one ring signature scheme with multi-designated verifiers in the literature and the scheme is based on the bilinear pairings which need to consume a lot of computation and under the traditional public key infrastructure (PKI). In order to improve computational efficiency and solve the problem of certificate management in PKI, in this paper, we propose the first identity-based ring signature scheme with multi-designated verifiers without pairings. We prove that our novel scheme's unforgeability, anonymity in the random oracle model and indistinguishability in the standard model under the intractability assumption of discrete logarithm problem and decisional Diffie-Hellman problem, and we prove that our novel scheme's non-transferability in the standard model. We compare the new scheme with a previous scheme in terms of computation and communication at last. The results show that our new scheme is more efficient than the previous scheme and is more suitable for the multi-user setting.

Scalable CCA-secure public-key authenticated encryption with keyword search from ideal lattices in cloud computing

Public-key authenticated encryption with keyword search (PAEKS) is an important cryptographic primitive for realizing effective and confidential searches on encrypted data in cloud computing. Several PAEKS schemes with various appealing functionalities have been proposed in the literature. Nevertheless, most of them are based on the classical number-theoretic assumptions and are impossible to resist quantum attacks. Their security is only proven against chosen-keyword attacks and is considered insufficient. Fortunately, ring-LWE and ring-ISIS problems reduced from the worst-case ideal lattices are believed to be post-quantum secure and could be improved computational efficiency in constructions. In this paper, we propose a scalable PAEKS scheme based on ring-LWE and ring-ISIS by adopting the ring analog of lattice algorithms of both digital signature and searchable encryption schemes, in which signature algorithms are used to authenticate ciphertext, making our PAEKS resistant to insider keyword guessing attacks. The scheme is also proved secure against chosen-ciphertext attacks and token privacy attacks. In addition, we extend the PAEKS scheme to conjunctive keywords and multi-user settings to allow for realistic promotion. We finally implement our schemes and compare them with related counterparts, which shows that our constructions are efficient in practical applications.

Digital compass for multi-user beam access in mmWave cellular networks

Beamforming in stand-alone Millimeter-Wave (mmWave) communications results in prolonged access times and latencies due to the increased number of measurements required to determine the optimal beam directions at the Mobile Station (MS) and Base Station (BS), returning the highest received signal level. Therefore, dynamic and fast access schemes that meet the Third-Generation Partnership Project (3GPP) specifications are required here. Therefore, in this paper, a novel initial access scheme is proposed for multiple MS users by leveraging for the first time a digital compass in the access procedure. Namely, when a new MS joins the footprint of a BS, it probes the channel for beacon signaling about the BS direction, i.e., broadcasted by a neighboring MS that completed beam association at previous time steps. Then, a digital compass is utilized to adjust the coordinates of the BS according to the location of the new MS. The proposed scheme is applied for a single and multi-user settings at various broadcasting approaches. This includes a single associated MS user that broadcasts information to a single incoming MS user, a single user that broadcasts signals to multiple incoming users, or all multiple associated users broadcast to multiple incoming users. Overall, the proposed schemes yield in notable efficiency in terms of the computational complexity, access times, power and energy consumption as compared to existing access schemes. Further, high success rates are achieved at the detriment of relatively higher cost.

VFIRM: Verifiable Fine-Grained Encrypted Image Retrieval in Multi-Owner Multi-User Settings

To ensure the security of images outsourced to the malicious cloud without affecting searchability on such outsourced (typically encrypted) images, one could use privacy-preserving Content-Based Image Retrieval (CBIR) primitive. However, conventional privacy-preserving CBIR schemes based on Searchable Symmetric Encryption (SSE) are not capable of supporting efficient fine-grained access control and result verification simultaneously. Therefore, in this article, we propose a <u>V</u> erifiable <u>F</u> ine-grained encrypted <u>I</u> mage <u>R</u> etrieval scheme in the <u>M</u> ulti-owner multi-user settings (VFIRM). VFIRM first utilizes a novel polynomial-based access strategy to provide efficient fine-grained access control. Then, it employs the dual secure <inline-formula><tex-math notation="LaTeX">$k$</tex-math></inline-formula> -nearest neighbor technique to distribute distinct keys to different data owners and data users, and finally implements an adapted homomorphic MAC technique to check the correctness of search results. Our formal security analysis shows that VFIRM is non-adaptive semantic secure if the client's search key is generated randomly and keeps in secret. Our empirical experiments using two real-world datasets (i.e., Caltech101 and Corel5k) demonstrate the practicality of VFIRM.

Efficient two-party SM2 signing protocol based on secret sharing

The digital signature is widely used in practice to verify a user’s identity and ensure data integrity for applications such as e-commerce and data exchange. The safe storage and reasonable use of the private key ensure the robustness of the cryptographic system. However, the private key stored in a single device faces the risk of invalidation due to theft or abuse. Moreover, the concentration of signature power inhibits their potential application in multi-user settings. Cooperative signature with the deployment of distributed key is a practical way to reduce the damage caused by key exposures. However, existing schemes of SM2 generally suffer from high computing overhead and exponential extension. In this paper, we present a new two-party SM2 protocol leveraging the Beaver’s multiplication that requires lower computational cost than previous two-party SM2 signing protocols. The proposed protocol is proven secure, as long as the standard SM2 signature scheme is secure. We implement our protocol in C to demonstrate that the proposed protocol has practical application prospects due to its efficiency advantage.

Triplex: an Efficient and One-Pass Leakage-Resistant Mode of Operation

This paper introduces and analyzes Triplex, a leakage-resistant mode of operation based on Tweakable Block Ciphers (TBCs) with 2n-bit tweaks. Triplex enjoys beyond-birthday ciphertext integrity in the presence of encryption and decryption leakage in a liberal model where all intermediate computations are leaked in full and only two TBC calls operating a long-term secret are protected with implementationlevel countermeasures. It provides beyond-birthday confidentiality guarantees without leakage, and standard confidentiality guarantees with leakage for a single-pass mode embedding a re-keying process for the bulk of its computations (i.e., birthday confidentiality with encryption leakage under a bounded leakage assumption). Triplex improves leakage-resistant modes of operation relying on TBCs with n-bit tweaks when instantiated with large-tweak TBCs like Deoxys-TBC (a CAESAR competition laureate) or Skinny (used by the Romulus finalist of the NIST lightweight crypto competition). Its security guarantees are maintained in the multi-user setting.

Privacy-preserving bidirectional keyword search over encrypted data for cloud-assisted IIoT

Cloud-assisted industrial Internet of Things (IIoT) technology is increasingly used by related enterprises. To preserve the privacy of sensitive data, IIoT devices must encrypt data before sending them to a cloud server. Public-key encryption with keyword search (PEKS) provides an important search function over cloud-assisted IIoT, allowing users to search for encrypted data without decryption. To increase practical functionality, Zhang et al. recently proposed the concept of public-key encryption with bidirectional keyword search, which supports both sender and receiver searches. However, their scheme provides insufficient security because it cannot resist keyword guessing attacks (KGA). Additionally, their scheme requires time-consuming bilinear pairing operations, resulting in high computational costs. In this study, a novel concept called public-key authenticated encryption with bidirectional keyword search was devised for multi-user settings. The system definition and security requirements are formally defined to ensure that no adversary can overcome the indistinguishability against chosen-keyword attacks or KGA. Furthermore, we propose a pairing-free semi-generic construction, combining a multiparty non-interactive protocol and authenticated functionality, which has proven to be secure under the standard model. The experimental results reveal that, compared with other state-of-the-art schemes, the proposed scheme is more practical, secure, and suitable for use with cloud-assisted IIoT systems.

Tight Security of Twin-DH Hashed ElGamal KEM in Multi-User Setting

Tight Security of Twin-DH Hashed ElGamal KEM in Multi-User Setting

Outer Bounds for Multiuser Settings: The Auxiliary Receiver Approach

This paper employs auxiliary receivers as a mathematical tool to identify Gallager-type auxiliary random variables and write outer bounds for some basic multiuser settings. This approach is then applied to the relay, interference, and broadcast channel settings, yielding new outer bounds that improve on existing outer bounds and strictly outperform classical outer bounds. For instance, we strictly improve on: the cutset outer bound for the scalar Gaussian relay channel, the outer bounds for the Gaussian Z-interference channel, and the outer bounds for the two receiver broadcast channel.

Lattice-based public-key encryption with conjunctive keyword search in multi-user setting for IIoT

Lattice-based public-key encryption with conjunctive keyword search in multi-user setting for IIoT

Revocable key aggregate searchable encryption with user privacy and anonymity

The KASE schemes allow fine-grained delegation of search rights over a selected dataset using an aggregate key. However, when the existing KASE schemes are deployed in real-time applications, the support of revocation of delegated rights is highly required to manage users' access control. Therefore, in this paper we propose two solutions for the fine-grained revocation of delegated rights considering two different scenarios. First, we present a basic scheme that supports fine-grained revocation of the delegated rights on document level, instead of coarse-grained all-or-nothing access. Then, the user is not allowed to search the document by the old trapdoor if his search privileges are revoked on that document. Under a multi-user setting, we propose an advance scheme that can make the fine-grained revocation of the delegated rights on the user level. The proposed approaches also preserve users' privacy and anonymity. We present the schemes' correctness proof, formal security analysis, and performance analysis, which confirm that they are provably secure and practically efficient.

Multi-User Virtual Reality for Remote Collaboration in Construction Projects: A Case Study with High-Rise Elevator Machine Room Planning

Virtual Reality (VR) is considered among the major technologies to address the inefficient collaboration issue caused by the predominant use of 2D drawings in the construction industry. However, there is still a knowledge gap between researchers and practitioners about the actual benefits of VR in the business context. This paper presents the benefits of VR usage in four real-life high-rise elevator projects from the user and business perspectives. Four VR environments of actual machine rooms for planning were created and tested in a multi-user setting. Overall, users find VR more intuitive than conventional tools to enhance planning accuracy and collaboration. The results also show that VR brings significant economic savings and gains for business in the industry. Future study should investigate the real cost-benefit ratio of VR and streamline its technical implementation within construction projects. The research contributes to the current body of knowledge by providing real-life economic benefits and directions to address the research gap in both academia and industry to promote the wide adoption of VR.