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L, Nirmala Devi, K, Venkata Subbareddy.  2019.  Secure and Composite Routing Strategy through Clustering In WSN. 2019 2nd International Conference on Innovations in Electronics, Signal Processing and Communication (IESC). :119–123.

Due to openness of the deployed environment and transmission medium, Wireless Sensor Networks (WSNs) suffers from various types of security attacks including Denial of service, Sinkhole, Tampering etc. Securing WSN is achieved a greater research interest and this paper proposes a new secure routing strategy for WSNs based on trust model. In this model, initially the sensor nodes of the network are formulated as clusters. Further a trust evaluation mechanism was accomplished for every sensor node at Cluster Head level to build a secure route for data transmission from sensor node to base station. Here the trust evaluation is carried out only at cluster head and also the cluster head is chosen in such a way the node having rich resources availability. The trust evaluation is a composition of the social trust and data trust. Simulation experiments are conducted over the proposed approach and the performance is measured through the performance metrics such as network lifetime, and Malicious Detection Rate. The obtained performance metrics shows the outstanding performance of proposed approach even in the increased malicious behavior of network.

L. Huiying, X. Caiyun, K. Jun, D. Ying.  2015.  "A Novel Secure Arithmetic Image Coding Algorithm Based on Two-Dimensional Generalized Logistic Mapping". 2015 Fifth International Conference on Instrumentation and Measurement, Computer, Communication and Control (IMCCC). :671-674.

A novel secure arithmetic image coding algorithm based on Two-dimensional Generalized Logistic Mapping is proposed. Firstly, according to the digital image size m×n, two 2D chaotic sequences are generated by logistic chaotic mapping. Then, the original image data is scrambled by sorting the chaotic sequence. Secondly, the chaotic sequence is optimized to generate key stream which is used to mask the image data. Finally, to generate the final output, the coding interval order is controlled by the chaotic sequence during the arithmetic coding process. Experiment results show the proposed secure algorithm has good robustness and can be applied in the arithmetic coder for multimedia such as video and audio with little loss of coding efficiency.

L. Rivière, J. Bringer, T. H. Le, H. Chabanne.  2015.  "A novel simulation approach for fault injection resistance evaluation on smart cards". 2015 IEEE Eighth International Conference on Software Testing, Verification and Validation Workshops (ICSTW). :1-8.

Physical perturbations are performed against embedded systems that can contain valuable data. Such devices and in particular smart cards are targeted because potential attackers hold them. The embedded system security must hold against intentional hardware failures that can result in software errors. In a malicious purpose, an attacker could exploit such errors to find out secret data or disrupt a transaction. Simulation techniques help to point out fault injection vulnerabilities and come at an early stage in the development process. This paper proposes a generic fault injection simulation tool that has the particularity to embed the injection mechanism into the smart card source code. By its embedded nature, the Embedded Fault Simulator (EFS) allows us to perform fault injection simulations and side-channel analyses simultaneously. It makes it possible to achieve combined attacks, multiple fault attacks and to perform backward analyses. We appraise our approach on real, modern and complex smart card systems under data and control flow fault models. We illustrate the EFS capacities by performing a practical combined attack on an Advanced Encryption Standard (AES) implementation.

L. Thiele, M. Kurras, S. Jaeckel, S. Fähse, W. Zirwas.  2015.  "Interference-floor shaping for liquid coverage zones in coordinated 5G networks". 2015 49th Asilomar Conference on Signals, Systems and Computers. :1102-1106.

Joint transmission coordinated multi-point (CoMP) is a combination of constructive and destructive superposition of several to potentially many signal components, with the goal to maximize the desired receive-signal and at the same time to minimize mutual interference. Especially the destructive superposition requires accurate alignment of phases and amplitudes. Therefore, a 5G clean slate approach needs to incorporate the following enablers to overcome the challenging limitation for JT CoMP: accurate channel estimation of all relevant channel components, channel prediction for time-aligned precoder design, proper setup of cooperation areas corresponding to user grouping and to limit feedback overhead especially in FDD as well as treatment of out-of-cluster interference (interference floor shaping).

La Manna, Michele, Perazzo, Pericle, Rasori, Marco, Dini, Gianluca.  2019.  fABElous: An Attribute-Based Scheme for Industrial Internet of Things. 2019 IEEE International Conference on Smart Computing (SMARTCOMP). :33–38.
The Internet of Things (IoT) is a technological vision in which constrained or embedded devices connect together through the Internet. This enables common objects to be empowered with communication and cooperation capabilities. Industry can take an enormous advantage of IoT, leading to the so-called Industrial IoT. In these systems, integrity, confidentiality, and access control over data are key requirements. An emerging approach to reach confidentiality and access control is Attribute-Based Encryption (ABE), which is a technique able to enforce cryptographically an access control over data. In this paper, we propose fABElous, an ABE scheme suitable for Industrial IoT applications which aims at minimizing the overhead of encryption on communication. fABElous ensures data integrity, confidentiality, and access control, while reducing the communication overhead of 35% with respect to using ABE techniques naively.
Laaboudi, Younes, Olivereau, Alexis, Oualha, Nouha.  2019.  An Intrusion Detection and Response Scheme for CP-ABE-Encrypted IoT Networks. 2019 10th IFIP International Conference on New Technologies, Mobility and Security (NTMS). :1–5.

This paper introduces a new method of applying both an Intrusion Detection System (IDS) and an Intrusion Response System (IRS) to communications protected using Ciphertext-Policy Attribute-based Encryption (CP-ABE) in the context of the Internet of Things. This method leverages features specific to CP-ABE in order to improve the detection capabilities of the IDS and the response ability of the network. It also enables improved privacy towards the users through group encryption rather than one-to-one shared key encryption as the policies used in the CP-ABE can easily include the IDS as an authorized reader. More importantly, it enables different levels of detection and response to intrusions, which can be crucial when using anomaly-based detection engines.

Laatansa, Saputra, Ragil, Noranita, Beta.  2019.  Analysis of GPGPU-Based Brute-Force and Dictionary Attack on SHA-1 Password Hash. 2019 3rd International Conference on Informatics and Computational Sciences (ICICoS). :1—4.
Password data in a system usually stored in hash. Various human-caused negligence and system vulnerability can make those data fall in the hand of those who isn't entitled to or even those who have malicious purpose. Attacks which could be done on the hashed password data using GPGPU-based machine are for example: brute-force, dictionary, mask-attack, and word-list. This research explains about effectivity of brute-force and dictionary attack which done on SHA-l hashed password using GPGPU-based machine. Result is showing that brute-force effectively crack more password which has lower set of character, with over 11% of 7 or less characters passwords vs mere 3 % in the dictionary attack counterpart. Whereas dictionary attack is more effective on cracking password which has unsecure character pattern with 5,053 passwords vs 491 on best brute-force attack scenario. Usage of combined attack method (brute-force + dictionary) gives more balanced approach in terms of cracking whether the password is long or secure patterned string.
Labib, N. S., Brust, M. R., Danoy, G., Bouvry, P..  2019.  Trustworthiness in IoT – A Standards Gap Analysis on Security, Data Protection and Privacy. 2019 IEEE Conference on Standards for Communications and Networking (CSCN). :1–7.
With the emergence of new digital trends like Internet of Things (IoT), more industry actors and technical committees pursue research in utilising such technologies as they promise a better and optimised management, improved energy efficiency and a better quality living through a wide array of value-added services. However, as sensing, actuation, communication and control become increasingly more sophisticated, such promising data-driven systems generate, process, and exchange larger amounts of security-critical and privacy-sensitive data, which makes them attractive targets of attacks. In turn this affirms the importance of trustworthiness in IoT and emphasises the need of a solid technical and regulatory foundation. The goal of this paper is to first introduce the concept of trustworthiness in IoT, its main pillars namely, security, privacy and data protection, and then analyse the state-of-the-art in research and standardisation for each of these subareas. Throughout the paper, we develop and refer to Unmanned Aerial Vehicles (UAVs) as a promising value-added service example of mobile IoT devices. The paper then presents a thorough gap analysis and concludes with recommendations for future work.
Lacerda, A., Rodrigues, J., Macedo, J., Albuquerque, E..  2017.  Deployment and analysis of honeypots sensors as a paradigm to improve security on systems. 2017 Internet Technologies and Applications (ITA). :64–68.
This article is about study of honeypots. In this work, we use some honeypot sensors deployment and analysis to identify, currently, what are the main attacks and security breaches explored by attackers to compromise systems. For example, a common server or service exposed to the Internet can receive a million of hits per day, but sometimes would not be easy to identify the difference between legitimate access and an attacker trying to scan, and then, interrupt the service. Finally, the objective of this research is to investigate the efficiency of the honeypots sensors to identify possible safety gaps and new ways of attacks. This research aims to propose some guidelines to avoid or minimize the damage caused by these attacks in real systems.
Lachner, Clemens, Rausch, Thomas, Dustdar, Schahram.  2019.  Context-Aware Enforcement of Privacy Policies in Edge Computing. 2019 IEEE International Congress on Big Data (BigDataCongress). :1—6.
Privacy is a fundamental concern that confronts systems dealing with sensitive data. The lack of robust solutions for defining and enforcing privacy measures continues to hinder the general acceptance and adoption of these systems. Edge computing has been recognized as a key enabler for privacy enhanced applications, and has opened new opportunities. In this paper, we propose a novel privacy model based on context-aware edge computing. Our model leverages the context of data to make decisions about how these data need to be processed and managed to achieve privacy. Based on a scenario from the eHealth domain, we show how our generalized model can be used to implement and enact complex domain-specific privacy policies. We illustrate our approach by constructing real world use cases involving a mobile Electronic Health Record that interacts with, and in different environments.
Lacroix, Alexsandre B., Langlois, J.M. Pierre, Boyer, François-Raymond, Gosselin, Antoine, Bois, Guy.  2016.  Node Configuration for the Aho-Corasick Algorithm in Intrusion Detection Systems. Proceedings of the 2016 Symposium on Architectures for Networking and Communications Systems. :121–122.

In this paper, we analyze the performance and cost trade-off from selecting two representations of nodes when implementing the Aho-Corasick algorithm. This algorithm can be used for pattern matching in network-based intrusion detection systems such as Snort. Our analysis uses the Snort 2.9.7 rules set, which contains almost 26k patterns. Our methodology consists of code profiling and analysis, followed by the selection of a parameter to maximize a metric that combines clock cycles count and memory usage. The parameter determines which of two types of nodes is selected for each trie node. We show that it is possible to select the parameter to optimize the metric, which results in an improvement by up to 12× compared with the single node-type case.

Lacroix, Jesse, El-Khatib, Khalil, Akalu, Rajen.  2016.  Vehicular Digital Forensics: What Does My Vehicle Know About Me? Proceedings of the 6th ACM Symposium on Development and Analysis of Intelligent Vehicular Networks and Applications. :59–66.

A major component of modern vehicles is the infotainment system, which interfaces with its drivers and passengers. Other mobile devices, such as handheld phones and laptops, can relay information to the embedded infotainment system through Bluetooth and vehicle WiFi. The ability to extract information from these systems would help forensic analysts determine the general contents that is stored in an infotainment system. Based off the data that is extracted, this would help determine what stored information is relevant to law enforcement agencies and what information is non-essential when it comes to solving criminal activities relating to the vehicle itself. This would overall solidify the Intelligent Transport System and Vehicular Ad Hoc Network infrastructure in combating crime through the use of vehicle forensics. Additionally, determining the content of these systems will allow forensic analysts to know if they can determine anything about the end-user directly and/or indirectly.

Lafram, Ichrak, Berbiche, Naoual, El Alami, Jamila.  2019.  Artificial Neural Networks Optimized with Unsupervised Clustering for IDS Classification. 2019 1st International Conference on Smart Systems and Data Science (ICSSD). :1–7.

Information systems are becoming more and more complex and closely linked. These systems are encountering an enormous amount of nefarious traffic while ensuring real - time connectivity. Therefore, a defense method needs to be in place. One of the commonly used tools for network security is intrusion detection systems (IDS). An IDS tries to identify fraudulent activity using predetermined signatures or pre-established user misbehavior while monitoring incoming traffic. Intrusion detection systems based on signature and behavior cannot detect new attacks and fall when small behavior deviations occur. Many researchers have proposed various approaches to intrusion detection using machine learning techniques as a new and promising tool to remedy this problem. In this paper, the authors present a combination of two machine learning methods, unsupervised clustering followed by a supervised classification framework as a Fast, highly scalable and precise packets classification system. This model's performance is assessed on the new proposed dataset by the Canadian Institute for Cyber security and the University of New Brunswick (CICIDS2017). The overall process was fast, showing high accuracy classification results.

Lago, Loris Dal, Ferrante, Orlando, Passerone, Roberto, Ferrari, Alberto.  2018.  Dependability Assessment of SOA-Based CPS With Contracts and Model-Based Fault Injection. IEEE Transactions on Industrial Informatics. 14:360—369.

Engineering complex distributed systems is challenging. Recent solutions for the development of cyber-physical systems (CPS) in industry tend to rely on architectural designs based on service orientation, where the constituent components are deployed according to their service behavior and are to be understood as loosely coupled and mostly independent. In this paper, we develop a workflow that combines contract-based and CPS model-based specifications with service orientation, and analyze the resulting model using fault injection to assess the dependability of the systems. Compositionality principles based on the contract specification help us to make the analysis practical. The presented techniques are evaluated on two case studies.

Lagraa, S., Cailac, M., Rivera, S., Beck, F., State, R..  2019.  Real-Time Attack Detection on Robot Cameras: A Self-Driving Car Application. 2019 Third IEEE International Conference on Robotic Computing (IRC). :102—109.

The Robot Operating System (ROS) are being deployed for multiple life critical activities such as self-driving cars, drones, and industries. However, the security has been persistently neglected, especially the image flows incoming from camera robots. In this paper, we perform a structured security assessment of robot cameras using ROS. We points out a relevant number of security flaws that can be used to take over the flows incoming from the robot cameras. Furthermore, we propose an intrusion detection system to detect abnormal flows. Our defense approach is based on images comparisons and unsupervised anomaly detection method. We experiment our approach on robot cameras embedded on a self-driving car.

Laguduva, Vishalini, Islam, Sheikh Ariful, Aakur, Sathyanarayanan, Katkoori, Srinivas, Karam, Robert.  2019.  Machine Learning Based IoT Edge Node Security Attack and Countermeasures. 2019 IEEE Computer Society Annual Symposium on VLSI (ISVLSI). :670—675.
Advances in technology have enabled tremendous progress in the development of a highly connected ecosystem of ubiquitous computing devices collectively called the Internet of Things (IoT). Ensuring the security of IoT devices is a high priority due to the sensitive nature of the collected data. Physically Unclonable Functions (PUFs) have emerged as critical hardware primitive for ensuring the security of IoT nodes. Malicious modeling of PUF architectures has proven to be difficult due to the inherently stochastic nature of PUF architectures. Extant approaches to malicious PUF modeling assume that a priori knowledge and physical access to the PUF architecture is available for malicious attack on the IoT node. However, many IoT networks make the underlying assumption that the PUF architecture is sufficiently tamper-proof, both physically and mathematically. In this work, we show that knowledge of the underlying PUF structure is not necessary to clone a PUF. We present a novel non-invasive, architecture independent, machine learning attack for strong PUF designs with a cloning accuracy of 93.5% and improvements of up to 48.31% over an alternative, two-stage brute force attack model. We also propose a machine-learning based countermeasure, discriminator, which can distinguish cloned PUF devices and authentic PUFs with an average accuracy of 96.01%. The proposed discriminator can be used for rapidly authenticating millions of IoT nodes remotely from the cloud server.
Laguna, Ignacio, Schulz, Martin, Richards, David F., Calhoun, Jon, Olson, Luke.  2016.  IPAS: Intelligent Protection Against Silent Output Corruption in Scientific Applications. Proceedings of the 2016 International Symposium on Code Generation and Optimization. :227–238.

This paper presents IPAS, an instruction duplication technique that protects scientific applications from silent data corruption (SDC) in their output. The motivation for IPAS is that, due to natural error masking, only a subset of SDC errors actually affects the output of scientific codes—we call these errors silent output corruption (SOC) errors. Thus applications require duplication only on code that, when affected by a fault, yields SOC. We use machine learning to learn code instructions that must be protected to avoid SOC, and, using a compiler, we protect only those vulnerable instructions by duplication, thus significantly reducing the overhead that is introduced by instruction duplication. In our experiments with five workloads, IPAS reduces the percentage of SOC by up to 90% with a slowdown that ranges between 1.04x and 1.35x, which corresponds to as much as 47% less slowdown than state-of-the-art instruction duplication techniques.

Lagunas, E., Rugini, L..  2017.  Performance of compressive sensing based energy detection. 2017 IEEE 28th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC). :1–5.

This paper investigates closed-form expressions to evaluate the performance of the Compressive Sensing (CS) based Energy Detector (ED). The conventional way to approximate the probability density function of the ED test statistic invokes the central limit theorem and considers the decision variable as Gaussian. This approach, however, provides good approximation only if the number of samples is large enough. This is not usually the case in CS framework, where the goal is to keep the sample size low. Moreover, working with a reduced number of measurements is of practical interest for general spectrum sensing in cognitive radio applications, where the sensing time should be sufficiently short since any time spent for sensing cannot be used for data transmission on the detected idle channels. In this paper, we make use of low-complexity approximations based on algebraic transformations of the one-dimensional Gaussian Q-function. More precisely, this paper provides new closed-form expressions for accurate evaluation of the CS-based ED performance as a function of the compressive ratio and the Signal-to-Noise Ratio (SNR). Simulation results demonstrate the increased accuracy of the proposed equations compared to existing works.

Lahbib, A., Toumi, K., Elleuch, S., Laouiti, A., Martin, S..  2017.  Link Reliable and Trust Aware RPL Routing Protocol for Internet of Things. 2017 IEEE 16th International Symposium on Network Computing and Applications (NCA). :1–5.

Internet of Things (IoT) is characterized by heterogeneous devices that interact with each other on a collaborative basis to fulfill a common goal. In this scenario, some of the deployed devices are expected to be constrained in terms of memory usage, power consumption and processing resources. To address the specific properties and constraints of such networks, a complete stack of standardized protocols has been developed, among them the Routing Protocol for Low-Power and lossy networks (RPL). However, this protocol is exposed to a large variety of attacks from the inside of the network itself. To fill this gap, this paper focuses on the design and the integration of a novel Link reliable and Trust aware model into the RPL protocol. Our approach aims to ensure Trust among entities and to provide QoS guarantees during the construction and the maintenance of the network routing topology. Our model targets both node and link Trust and follows a multidimensional approach to enable an accurate Trust value computation for IoT entities. To prove the efficiency of our proposal, this last has been implemented and tested successfully within an IoT environment. Therefore, a set of experiments has been made to show the high accuracy level of our system.

Lahrouni, Youssef, Pereira, Caroly, Bensaber, Boucif Amar, Biskri, Ismaïl.  2017.  Using Mathematical Methods Against Denial of Service (DoS) Attacks in VANET. Proceedings of the 15th ACM International Symposium on Mobility Management and Wireless Access. :17–22.

VANET network is a new technology on which future intelligent transport systems are based; its purpose is to develop the vehicular environment and make it more comfortable. In addition, it provides more safety for drivers and cars on the road. Therefore, we have to make this technology as secured as possible against many threats. As VANET is a subclass of MANET, it has inherited many security problems but with a different architecture and DOS attacks are one of them. In this paper, we have focused on DOS attacks that prevent users to receive the right information at the right moment. We have analyzed DOS attacks behavior and effects on the network using different mathematical models in order to find an efficient solution.

Lai, Chengzhe, Du, Yangyang, Men, Jiawei, Zheng, Dong.  2019.  A Trust-based Real-time Map Updating Scheme. 2019 IEEE/CIC International Conference on Communications in China (ICCC). :334—339.

The real-time map updating enables vehicles to obtain accurate and timely traffic information. Especially for driverless cars, real-time map updating can provide high-precision map service to assist the navigation, which requires vehicles to actively upload the latest road conditions. However, due to the untrusted network environment, it is difficult for the real-time map updating server to evaluate the authenticity of the road information from the vehicles. In order to prevent malicious vehicles from deliberately spreading false information and protect the privacy of vehicles from tracking attacks, this paper proposes a trust-based real-time map updating scheme. In this scheme, the public key is used as the identifier of the vehicle for anonymous communication with conditional anonymity. In addition, the blockchain is applied to provide the existence proof for the public key certificate of the vehicle. At the same time, to avoid the spread of false messages, a trust evaluation algorithm is designed. The fog node can validate the received massages from vehicles using Bayesian Inference Model. Based on the verification results, the road condition information is sent to the real-time map updating server so that the server can update the map in time and prevent the secondary traffic accident. In order to calculate the trust value offset for the vehicle, the fog node generates a rating for each message source vehicle, and finally adds the relevant data to the blockchain. According to the result of security analysis, this scheme can guarantee the anonymity and prevent the Sybil attack. Simulation results show that the proposed scheme is effective and accurate in terms of real-time map updating and trust values calculating.

Lai, Chengzhe, Ding, Yuhan.  2019.  A Secure Blockchain-Based Group Mobility Management Scheme in VANETs. 2019 IEEE/CIC International Conference on Communications in China (ICCC). :340–345.

Vehicular Ad-hoc Network (VANET) can provide vehicle to vehicle (V2V) and vehicle to infrastructure (V2I) communications for efficient and safe transportation. The vehicles features high mobility, thus undergoing frequent handovers when they are moving, which introduces the significant overload on the network entities. To address the problem, the distributed mobility management (DMM) protocol for next generation mobile network has been proposed, which can be well combined with VANETs. Although the existing DMM solutions can guarantee the smooth handovers of vehicles, the security has not been fully considered in the mobility management. Moreover, the most of existing schemes cannot support group communication scenario. In this paper, we propose an efficient and secure group mobility management scheme based on the blockchain. Specifically, to reduce the handover latency and signaling cost during authentication, aggregate message authentication code (AMAC) and one-time password (OTP) are adopted. The security analysis and the performance evaluation results show that the proposed scheme can not only enhance the security functionalities but also support fast handover authentication.

Lai, Chia-Min, Lu, Chia-Yu, Lee, Hahn-Ming.  2018.  Implementation of Adversarial Scenario to Malware Analytic. Proceedings of the 2Nd International Conference on Machine Learning and Soft Computing. :127–132.

As the worldwide internet has non-stop developments, it comes with enormous amount automatically generated malware. Those malware had become huge threaten to computer users. A comprehensive malware family classifier can help security researchers to quickly identify characteristics of malware which help malware analysts to investigate in more efficient way. However, despite the assistance of the artificial intelligent (AI) classifiers, it has been shown that the AI-based classifiers are vulnerable to so-called adversarial attacks. In this paper, we demonstrate how the adversarial settings can be applied to the classifier of malware families classification. Our experimental results achieved high successful rate through the adversarial attack. We also find the important features which are ignored by malware analysts but useful in the future analysis.

Lai, J., Duan, B., Su, Y., Li, L., Yin, Q..  2017.  An active security defense strategy for wind farm based on automated decision. 2017 IEEE Power Energy Society General Meeting. :1–5.

With the development of smart grid, information and energy integrate deeply. For remote monitoring and cluster management, SCADA system of wind farm should be connected to Internet. However, communication security and operation risk put forward a challenge to data network of the wind farm. To address this problem, an active security defense strategy combined whitelist and security situation assessment is proposed. Firstly, the whitelist is designed by analyzing the legitimate packet of Modbus on communication of SCADA servers and PLCs. Then Knowledge Automation is applied to establish the Decision Requirements Diagram (DRD) for wind farm security. The D-S evidence theory is adopted to assess operation situation of wind farm and it together with whitelist offer the security decision for wind turbine. This strategy helps to eliminate the wind farm owners' security concerns of data networking, and improves the integrity of the cyber security defense for wind farm.

Lai, Shangqi, Patranabis, Sikhar, Sakzad, Amin, Liu, Joseph K., Mukhopadhyay, Debdeep, Steinfeld, Ron, Sun, Shi-Feng, Liu, Dongxi, Zuo, Cong.  2018.  Result Pattern Hiding Searchable Encryption for Conjunctive Queries. Proceedings of the 2018 ACM SIGSAC Conference on Computer and Communications Security. :745–762.

The recently proposed Oblivious Cross-Tags (OXT) protocol (CRYPTO 2013) has broken new ground in designing efficient searchable symmetric encryption (SSE) protocol with support for conjunctive keyword search in a single-writer single-reader framework. While the OXT protocol offers high performance by adopting a number of specialised data-structures, it also trades-off security by leaking 'partial' database information to the server. Recent attacks have exploited similar partial information leakage to breach database confidentiality. Consequently, it is an open problem to design SSE protocols that plug such leakages while retaining similar efficiency. In this paper, we propose a new SSE protocol, called Hidden Cross-Tags (HXT), that removes 'Keyword Pair Result Pattern' (KPRP) leakage for conjunctive keyword search. We avoid this leakage by adopting two additional cryptographic primitives - Hidden Vector Encryption (HVE) and probabilistic (Bloom filter) indexing into the HXT protocol. We propose a 'lightweight' HVE scheme that only uses efficient symmetric-key building blocks, and entirely avoids elliptic curve-based operations. At the same time, it affords selective simulation-security against an unbounded number of secret-key queries. Adopting this efficient HVE scheme, the overall practical storage and computational overheads of HXT over OXT are relatively small (no more than 10% for two keywords query, and 21% for six keywords query), while providing a higher level of security.