Related Schemes Research Articles

Identification of homogeneous chemical kinetic regimes of methane-air ignition

Sensitivity analysis results for ignition delay time (IDT) may be very different depending on the initial temperature, pressure and equivalence ratio φ, but similar in some regions of these variables. This phenomenon was investigated systematically by carrying out ignition simulations and local sensitivity calculations of methane−air mixtures using the Aramco-II-2016 mechanism at 14,417 combinations of initial temperature (changed between 500 and 3000 K), initial pressure (0.05−500 atm) and φ (0.05−8.0) values. The cluster analysis of the sensitivity vectors identified five large kinetically homogeneous regions. Each region has well defined borders in the (T, p φ) space and can be characterized by different sets of important reactions. The related kinetic scheme is very different in each region. Regions 1 and 2 are dominated by catalytic cycles based on species CH3O2/CH3O2H and HO2/H2O2/CH3O, respectively. In regions 3, 4, and 5 the H atoms are converted to CH3 in an identical chain branching sequence, but the back conversion is via three different routes. Literature experimental data on the IDTs of methane−air mixtures were sorted according to these five regions. Regions 1 to 5 contain 214, 328, 3, 0, and 237 experimental data points, respectively. In regions 1, 2 and 5 the data points are well reproduced by the Aramco-II-2016 mechanism, but little or no experimental information is available about kinetic regions 3 and 4. Further experimental exploration of the ignition of methane−air mixtures may aim the study of these regions. A similar approach can be used for the characterization of other combustion systems and sorting the related experimental data.

A Robust Authentication Protocol for Wireless Medical Sensor Networks Using Blockchain and Physically Unclonable Functions

Wireless medical sensor networks (WMSNs)-based medical systems are an emerging paradigm of the Internet of Medical Things (IoMT) in which the patients and doctors can access various healthcare services via wireless communication technology without visiting the hospital in person. However, an adversary attempts a variety of security attacks because the sensitive information in various fields is exchanged via an insecure channel. Thus, robust and lightweight authentication protocols are essential for providing dependable healthcare services in WMSN-based medical systems. Recently, Wang et al. (IEEE Internet of Things Journal, doi: 10.1109/JIOT.2021.3117762) proposed blockchain and physically unclonable functions (PUFs)-based lightweight authentication protocol for WMSN. They claimed that their protocol is resistant to cyber and physical security threats and also does provide necessary security requirements. However, we prove that their protocol is vulnerable to various security attacks, such as man-in-the-middle and session key disclosure attacks and also lacks mutual authentication. As a result, we propose a robust authentication protocol for WMSN using blockchain and PUF to address the security problems raised by Wang et al.’s scheme. we assess the security of the proposed scheme by using informal and formal security analyses, such as AVISPA simulation and the ROR oracle model. Furthermore, we present the testbed experiments using Raspberry PI 4 based on MIRACL Crypto SDK. Then, we show the performance of the enhanced scheme compared with related schemes based on testbed experiments. Consequently, our scheme is better suited for practical WMSN-based medical systems because it provides greater security and efficiency than competing schemes.

A biometrics-based mutual authentication and key agreement protocol for TMIS using elliptic curve cryptography.

Telecare Medicine Information System (TMIS) refers to a medical model that uses communication and information technology to realize multiple medical functions such as remote disease diagnosis, treatment, and health care. Because TMIS is carried out on an insecure public Internet, a large number of mutual authentication and key agreement protocols for TMIS have been proposed to protect the privacy of patients. Recently, Ostad-Sharif et al. proposed a novel anonymous authentication and key agreement scheme for TMIS. In this work, we will demonstrate that Ostad-Sharif et al.’s scheme exists the problems of strong authentication and inefficient password change, and it cannot resist the off-line password guessing attack. To overcome the weaknesses found in Ostad-Sharif et al.’s scheme, we propose a biometrics-based mutual authentication and key agreement protocol for TMIS, making full use of the advantages of one-way hash function and elliptic curve cryptosystem (ECC). The security of the proposed scheme is formally proved under the widely used random oracle model (ROM), and various known malicious attack resistances also are presented by the heuristic discussion. Compared with the existing related schemes, the computation cost and communication overhead of our scheme are reduced by 74.5% and 27.3% respectively.

Privacy preserving IoT-based crowd-sensing network with comparable homomorphic encryption and its application in combating COVID19

IoT-based crowd-sensing network, which aims to achieve data collection and task allocation to mobile users, become more and more popular in recent years. This data collected by IoT devices may be private and directly transmission of these data maybe incur privacy leakage. With the help of homomorphic encryption (HE), which supports the additive and/or multiplicative operations over the encrypted data, privacy preserving crowd-sensing network is now possible. Until now several such secure data aggregation schemes based on HE have been proposed. In many cases, ciphertext comparison is an important step for further secure data processing. However efficient ciphertext comparison is not supported by most such schemes. In this paper, aiming at enabling ciphertext comparison among multiple users in crowd-sensing network, with Lagrange’s interpolation technique we propose comparable homomorphic encryption (CompHE) schemes. We also prove our schemes’ security, and the performance analysis show our schemes are practical. We also discuss the applications of our IoT based crowd-sensing network with comparable homomorphic encryption for combatting COVID19, including the first example of privacy preserving close contact determination based on the spatial distance, and the second example of privacy preserving social distance controlling based on the spatial difference of lockdown zones, controlled zones and precautionary zones. From the analysis we see our IoT based crowd-sensing network can be used for contact tracing without worrying about the privacy leakage. Compared with the existing CompHE schemes, our proposals can be collusion resistance or secure in the semi-honest model while the previous schemes cannot achieve this easily. Our schemes only need 4 or 5 modular exponentiation when implementing the most important comparison algorithm, which are better than the existing closely related scheme with advantage of 50% or 37.5%.

FBCU-Net: A fine-grained context modeling network using boundary semantic features for medical image segmentation

The performance of deep learning-based medical image segmentation methods largely depends on the segmentation accuracy of tissue boundaries. However, since the boundary region is at the junction of areas of different categories, the pixels located at the boundary inevitably carry features belonging to other classes and difficult to distinguish. This paper proposes a fine-grained contextual modeling network for medical image segmentation based on boundary semantic features, FBCU-Net, which uses the semantic features of boundary regions to reduce the influence of irrelevant features on boundary pixels. First, based on the discovery that indistinguishable pixels are usually boundary pixels in medical images, we introduce new supervision information to find and classify boundary pixels. Second, based on the existing relational context modeling schemes, we generate the boundary region representations representing the semantic features of boundary regions. Last, we use boundary region representations to reduce the influence of irrelevant features on boundary pixels and generate highly discriminative pixel representations. Furthermore, to enhance the attention of the network to the boundary region, we also propose the boundary enhancement strategy. We evaluate the proposed model on five datasets, TUI (Thyroid Tumor), ISIC-2018 (Dermoscopy), 2018 Data Science Bowl (Cell Nuclei), Glas (Colon Cancer), and BUSI (Breast Cancer). The results show that FBCU-Net has better boundary segmentation performance and overall performance for different medical images than other state-of-the-art (SOTA) methods, and has great potential for clinical application.

SLAP-IoD: Secure and Lightweight Authentication Protocol Using Physical Unclonable Functions for Internet of Drones in Smart City Environments

With the emergence of the concept of smart city and the increasing demands for a range of drones, Internet of Drones (IoD) has achieved a variety of attention by providing multiple benefits in academia and industry. IoD offers numerous services, such as traffic monitoring, environmental monitoring, and disaster management by combining infrastructure, Internet of Things (IoT), and Flying Ad-Hoc Networks (FANET) in smart city environments. However, communication among drones is vulnerable to potential security threats because the sensitive messages in various applications are exchanged via an insecure channel in IoD-based smart city environments. Since IoDs can be operated in unattended environment with minimum human interventions, smart devices (e.g., drones and sensors) deployed in IoD architectures are vulnerable to physical capture attacks. In addition, drones are resource-constrained in terms of computation and communication overheads, and it is not much viable to apply public key cryptography (PKC) that requires high computation and communication overheads. Thus, we design a secure and lightweight authentication protocol using a physical unclonable function (PUF) for IoD to guarantee reliable and useful services in smart city environments, called SLAP-IoD. We prove the security of the SLAP-IoD using informal and formal security analyses using the broadly recognized Real-Or-Random (ROR) random oracle model, and also through the formal security verification using the widely-accepted Automated Validation of Internet Security-sensitive Protocols and Applications (AVISPA) security verification. Furthermore, we compare the performance of the SLAP-IoD with related schemes. Consequently, we show that SLAP-IoD offers better security and efficiency than other related schemes and is suitable for IoD-based smart city environments.

Two-Dimensional Behavior-Marker-Based Data Forwarding Incentive Scheme for Fog-Computing-Based SIoVs

In social Internet of Vehicles (SIoVs), vehicles can usually act as data-relaying nodes to forward data. However, vehicle nodes often show their personal and social selfishness in data forwarding (namely vehicle nodes are not willing to forward data), whose selfishness greatly influences the delivery ratio of data forwarding. In this article, we propose a 2-D behavior-marker-based data-forwarding incentive scheme to motivate vehicle nodes to participate in data forwarding in fog-computing-based SIoVs. First, we design a 2-D behavior marker mechanism, which can be used to completely evaluate vehicle nodes. Second, we construct a currency credit-based data-forwarding incentive strategy based on the 2-D marker and the social attributes of vehicle nodes, which is used to deal with vehicular normal behavior, vehicular selfish behavior, and vehicular malicious behavior. Compared with other related schemes, our proposed scheme can completely evaluate the behaviors of vehicle nodes and can further promote the cooperation of data-forwarding between selfish nodes. The experimental results show that our scheme is more efficient and stable in data forwarding in fog-computing-based SIoVs.

Blockchain-Based Reliable and Efficient Certificateless Signature for IIoT Devices

Nowadays, the Industrial Internet of Things (IIoT) has remarkably transformed our personal lifestyles and society operations into a novel digital mode, which brings tremendous associations with all walks of life, such as intelligent logistics, smart grid, and smart city. Moreover, with the rapid increase of IIoT devices, a large amount of data is swapped between heterogeneous sensors and devices every moment. This trend increases the risk of eavesdropping and hijacking attacks in communication channels, so maintaining data privacy and security becomes two notable concerns at present. Recently, based on the mechanism of the Schnorr signature, a more secure and lightweight certificateless signature (CLS) protocol is popular for the resource-constrained IIoT protocol design. Nevertheless, we found most of the existing CLS schemes are susceptible to several common security weaknesses such as man-in-the-middle attacks, key generation center compromised attacks, and distributed denial of service attacks. To tackle the challenges mentioned previously, in this article, we propose a novel pairing-free certificateless scheme that utilizes the state-of-the-art blockchain technique and smart contract to construct a novel reliable and efficient CLS scheme. Then, we simulate the Type-I and Type-II adversaries to verify the trustworthiness of our scheme. Security analysis as well as performance evaluation outcomes prove that our design can hold more reliable security assurance with less computation cost (i.e., reduced by around 40.0% at most) and communication cost (i.e., reduced by around 94.7% at most) than other related schemes.

Assessing Socio-Environmental Externalities of Big Hydro Power Projects: The Case of Skavica

The transition towards renewable energy sources has increased the interest in Hydro Power generation. The socio-environmental externalities produced from big HPPs have a significant impact on the local communities and on the overall economy of the country. There is consensus in the literature that small HPPs cause fewer and less severe environmental and social externalities than large HPPs. Anyway, the electricity supply is guaranteed by bigger investments and the trade-off is not quite simple to clarify. The study is based on a set of sustainability indicators which provide a life cycle analysis of the Skavica Hydro Power Plant and the relative investment scheme. The aim of this paper is to identify the general externalities related to the construction of a big HPP and to connect to the specific case study of Skavica HPP. Furthermore, the estimation of benefits and costs along with public discussions is integrated to evidence the legitimate social and environmental concerns of people living in areas where dams are planned. Policy options intended to adopt these externalities are also addressed.
 Keyword: Hydro Power Plant, renewable energy, Skavica, externalities, policy, floodings prevention, electricity

Relative Stereovision-Based Navigation for Noncooperative Spacecraft via Feature Extraction

Spacecraft proximity operations play an important role in guaranteeing the capture success of noncooperative targets. This article technically presents a relative stereovision-based navigation scheme that ensures accurate relative pose measurement as well as practical motion estimation for proximity operations. Specifically, features parameters of the line and circle on the noncooperative target are first obtained by the different image processing extraction algorithms. Then, the center position and normal of the circle are derived by orthogonal transformation from the circle feature parameters, and two features descriptors are defined by the redundant parameters in the stereovision to evaluate error levels of the extraction algorithms. In particular, the unavailable roll angle around the circle normal is recovered by incorporating the line and the descriptors by utilizing the least squares method, wherein the relative attitude is proved less affected by the features extraction errors, and thus, the measurement accuracy is theoretically improved. Furthermore, considering the Mahalanobis distances of the attitude and position, two outlier detectors are coupled with the 3 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sigma$</tex-math></inline-formula> rule in a multiplicative extended Kalman filter to achieve outlier rejection and motion estimation, respectively. Finally, numerical simulation and physical experiment are given to validate the effectiveness of the proposed approach.

TFPPASV: A Three-Factor Privacy Preserving Authentication Scheme for VANETs

A vehicular ad hoc network (VANET) is essential for the autonomous vehicle industry, and with the advancement in VANET technology, security threats are increasing rapidly. Mitigation of these threats needs an intelligent security protocol that provides unbreakable security. In recent times, various three-factor authentication solutions for VANET were introduced that adopt the centralized Trusted Authority T A , which is responsible for assigning authentication parameters during vehicle registration, and the authentication process depends on these parameters. This article first explains the vulnerabilities of the recent three-factor (3F) authentication scheme presented by Xu et al. Our analysis proves that if an RSU is dishonest, it can easily bypass the T A and can create a session with OBU . Furthermore, this paper puts forward a new scheme that provides the 3F authentication for VANETs (TFPPASV) to resist RSU from bypassing the T A and to offer user privacy. The proposed scheme fulfills the security and performance requirements of the VANET. We use BAN-Logic analysis to perform a formal security analysis of the proposed scheme, in addition to the informal security feature discussion. Finally, we compare the security and performance of the proposed TFPPASV with some recent and related schemes.

PUF-PSS: A Physically Secure Privacy-Preserving Scheme Using PUF for IoMT-Enabled TMIS

With the development of telecare medical information system (TMIS), doctors and patients are able to access useful medical services via 5G wireless communications without visiting the hospital in person. Unfortunately, TMIS should have the essential security properties, such as anonymity, mutual authentication, and privacy, since the patient’s data is transmitted via a public channel. Moreover, the sensing devices deployed in TMIS are resource-limited in terms of communication and computational costs. Thus, we design a physically secure privacy-preserving scheme using physical unclonable functions (PUF) in TMIS, called PUF-PSS to resolve the security requirements and efficiency of the existing related schemes. PUF-PSS prevents the security threats and also guarantees anonymity, key freshness, and authentication. We evaluate the security of PUF-PSS by performing formal and informal security analyses, including AVISPA implementation and ROR oracle model. We perform the test bed experiments utilizing well-known MIRACL based on a Raspberry PI 4 and compare the communication and computational costs of PUF-PSS with the previous schemes for TMIS. Consequently, PUF-PSS guarantees better efficiency and security than previous schemes and can be applied to TMIS environments.

Proposal for a Suicide Risk Assessment Protocol (Procedura Oceny Ryzyka Samobójczego, PORS) – protection of health and life of patients in psychiatric hospitals

As estimated by the World Health Organization, suicide, which defined as an act of intentionally taking one’s own life, accounts for approximately 1.4% of all deaths worldwide. There are many concepts of suicide, including those based on the cognitive theory – suicidal cognitive mode theory, interpersonal theory of suicide, or on the integrated motivational-volitional model of suicide. Suicide attempts can be made by both mentally ill people and people in crisis (suffering from, for example, adjustment disorder). A reliable and standardised procedure of suicidal risk assessment for patients in Polish psychiatric hospitals is currently missing, hence it was decided to develop a suicidal behaviour risk assessment model that would improve the quality of therapeutic work and maximise the protection of health and life of psychiatric patients. The procedure is to be understood as a set of activities primarily involving psychological and psychiatric examination. The lack of psychological procedures for assessing risk factors and protective factors at the State Hospital for Mental Diseases in Rybnik mobilised a team of specialists to develop the PORS (Procedura Oceny Ryzyka Samobójczego – Suicide Risk Assessment Protocol) model as a proposal for data collection, assessment and intervention in patients with a suicidal riswk. It was proposed to start the suicidal risk assessment with determining the severity of risk factors, which include, inter alia, mental disorders, sudden situational factors (in combination with personality traits) as well as substance abuse. The initial and final risk assessment allows to estimate not only the presence of predictors that increase suicidal tendencies, but also the actual risk of an intentional suicide attempt. PORS is a kind of systematisation of knowledge and experience in working with a patient with suicidal thoughts, intentions, or after a suicide attempt. The individual stages of psychological and psychiatric procedures contain guidelines and schemes in relation to the individual needs of a patient at risk of suicide.

L’Attachement dans les Troubles Dépressifs Persistants chez l’adulte : une revue de la littérature

Persistent depressive disorders (PDD) are frequent and disabling and their therapeutic management remains poorly defined. Attachment theory highlights the effect of insecure representations of relationships in the development and maintenance of PDD. The aim of this literature review is to identify the main findings regarding the place of attachment in persistent depressive disorders (PDD) to show the interest of this framework as an explanatory model of PDD and to determine the usefulness of taking attachment into consideration in the therapeutic intervention for the treatment of PDD. The current treatment of PDD faces a high rate of either failure or partial remission. Almost half of depressed patients do not achieve remission or develop chronic residual symptoms. Although there is a specific therapy built for PDD (CBASP), there is currently no psychotherapy that has been sufficiently scientifically verified to be recommended for PDD. Interpersonal difficulties seem to play a major role in the maintenance of a depressive state: the difficulty in establishing a therapeutic relationship would explain why patients with PDD often show a poor therapeutic response to traditional psychotherapies, including cognitive behavioural therapy (CBT). In addition, some characteristics that make treatment difficult may be a consequence of childhood maltreatment, in particular emotional abuse, and neglect, that are risk factors for early depression with a chronic course. Furthermore, insecure attachment is a major risk factor of severity or persistence of psychopathological disorders. Conversely, secure attachment reduces the risk of developing these symptoms. Empirical research has shown links between insecure attachment and specific psychological disorders. Insecure attachment is associated with internalizing disorders, including depression, in childhood and in adulthood. Insecure attachment is clearly associated with depressive symptoms. This relationship is mediated by several variables such as self-esteem, disrupted social and relational skills depressive cognitions and early maladaptive schemas. Taken together, these findings suggest that attachment is an important risk factor in the development of psychopathology, in particular depressive disorders. Therefore, Bosmans suggests that the integration of attachment into psychotherapies would enhance their effectiveness. Attachment should therefore be considered as an important target of clinical intervention to treat the symptoms of PDD and there seems to be a need to develop this therapeutic approach to determine the extent to which a treatment protocol can focus specifically on attachment for chronically depressed patients. Studies of attachment psychotherapies consider attachment style both as a predictor of treatment outcome and as an indicator of therapeutic orientation. The patient's attachment representations and behaviours can influence the therapeutic process and the relationship with the therapist, which means identifying them to use specific strategies: therapeutic techniques relevant to one attachment style may be problematic for another. These considerations show the need for research that considers the relationship between PDD symptoms and patients’ attachment styles at the beginning of therapy to verify which attachment patterns are related to this specific pathology and to determine the influence of patients’ attachment patterns on the therapeutic process. Finally, innovative therapies such as Integrated Attachment Therapy, that consider attachment as the foundation of the therapeutic process, are being developed and form a new care offer that seems promising for the treatment of PDD.

A blockchain-based conditional privacy-preserving authentication scheme for edge computing services

Edge computing is a new paradigm, especially suitable for Internet of Things (IoT) applications, which require low latency, location awareness and mass connections. It surely makes up for some shortcomings in cloud computing in terms of energy consumption and real-time analysis areas. However, it is still a great challenge to guarantee data security and privacy protection in edge computing environment. In this paper, we focus on the topic of authentication in edge computing and propose a conditional privacy-preserving authentication scheme based on blockchain, which guarantees user anonymity, conditional traceability as well as multi-factor security. The scheme uses elliptic curve cryptography (ECC) and does not use bilinear pairing operations. The key materials are stored on the blockchain and managed by the smart contracts. Formal security proof and heuristic security analysis show that the protocol satisfies desired security requirements and resists against most kinds of conventional attacks. Moreover, the performance comparison shows that the proposed scheme is more efficient in computation and communication than previous related schemes.

Contextuality, interculturality and decolonisation as schemes of power relations

HTS Teologiese Studies/Theological Studies is an acclaimed journal with broad coverage that promotes multidisciplinary, religious, and biblical aspects of studies in the international theological arena. The journal’s publication criteria are based on high ethical standards and the rigor of the methodology and conclusions reported.

UWB/INS-based robust anchor-free relative positioning scheme for UGVs

With the development of new distributed cluster applications such as distributed radar and UGV cooperation, the concept of relative positioning springs up—different from the classic positioning application, relative positioning focuses on the real-time determination of relative position relationships in multi-node networks without pre-deployment anchor, prior map and GNSS. Under such application conditions, relative localization also requires high real-time performance, and high accuracy in short baseline scenes, and can solve the positioning failure caused by occlusion and other factors. A high-precision relative positioning scheme based on UWB-INS fusion is proposed in this paper: a robust relative positioning algorithm based on iterative extended Kalman filter is optimized by modeling the system error state, and the adaptive residual elimination algorithm is introduced to ensure the robustness of positioning service. A series of experiments show that the scheme proposed in this paper can provide centimeter-level real-time positioning service for multi-node dynamic networks without anchors and maps, and is expected to become a potential effective relative positioning technology scheme.

Query answering over inconsistent knowledge bases: A probabilistic approach

Consistent query answering (CQA) is a widely accepted paradigm for querying inconsistent knowledge bases (KBs). A consistent answer to a query is a tuple that is an answer to the query over every repair of the KB, which is in turn a consistent KB whose extensional knowledge “minimally” differs from the original one's. This coarse-grained classification of answers into consistent and non-consistent ones lacks any information about their degree of consistency, i.e., how likely it is that a tuple is an answer to the query, when considering all the repaired KBs. To overcome this limitation, we consider a fine-grained notion of repair for KBs with equality-generating dependencies (EGDs), based on attribute-level updates, and exploit this notion to propose a probabilistic CQA approach, which associates a confidence to each answer, thereby providing more informative query answers. We first show that computing the query answer confidence is #P-hard. Then, in the light of this intractability result, we study the existence of efficient randomized, approximation schemes. In particular, we show that absolute error approximation schemes always exist in the general case, while more refined relative error approximation schemes, i.e., fully polynomial-time, randomized approximation schemes (FPRAS) exist when assuming that the constraints of the knowledge base are primary keys. Finally, we extend our framework to knowledge bases with tuple-generating dependencies (TGDs) and generalize our approximability results to the new setting, and prove additional inapproximability results.

High-quality visually secure image cryptosystem using improved Chebyshev map and 2D compressive sensing model

In this paper, we propose an improved Chebyshev map and a visually meaningful image encryption (VMIE) algorithm based on two-dimensional compressive sensing (2DCS). First, the adoption of 2DCS compresses the plain image, wherein the measurement matrix is processed by the simulated annealing algorithm to improve the quality of the reconstructed image. Second, a diffusion operation is performed on the sample data. Furthermore, a matrix encoding matrix is employed to insert the cryptographic image into the host image to obtain a visually meaningful steganographic image. The experimental results and comprehensive analyses show that the proposed scheme has feasible performance and stands up to various attacks. Eventually, the comparison with existing related schemes demonstrates that the proposed image encryption system has the advantages of visual security and reconstruction quality.

An energy-efficient and secure identity based RFID authentication scheme for vehicular cloud computing

Vehicular Cloud Computing (VCC) is a contemporary paradigm that includes the Internet of Things (IoT), cloud computing, and vehicular networking technologies. VCC offers vehicle-to-device, vehicle-to-infrastructure, and vehicle-to-vehicle communication in which the vehicles can communicate using sensing abilities. VCC is exploiting the IoT environment, cloud architecture, and vehicle resources. However, the energy-efficient privacy of communicators and security of communication are assertive problems in VCC. To accomplish this goal, we present an identity-based authentication scheme for VCC which also uses radio frequency identification (RFID). The security and robustness of the devised scheme are evaluated using informal and formal analysis. The informal analysis shows that our scheme is vigorous to resist various attacks. The formal analysis is done through Random Oracle Model (ROM) which shows that the scheme is secure and efficient. The performance of our scheme is also determined and compared with various related schemes which clearly illustrate the efficiency of the proposed scheme. Thus, our scheme is very efficient for employment in the VCC environment.