Visible to the public Biblio

Found 6908 results

Filters: Keyword is Metrics  [Clear All Filters]
Yu, Yue, Yao, Jiming, Wang, Wei, Qiu, Lanxin, Xu, Yangzhou.  2022.  A Lightweight Identity-Based Secondary Authentication Method in Smart Grid. 2022 IEEE 10th Joint International Information Technology and Artificial Intelligence Conference (ITAIC). 10:2190—2195.
5G network slicing plays a key role in the smart grid business. The existing authentication schemes for 5G slicing in smart grids require high computing costs, so they are time-consuming and do not fully consider the security of authentication. Aiming at the application scenario of 5G smart grid, this paper proposes an identity-based lightweight secondary authentication scheme. Compared with other well-known methods, in the protocol interaction of this paper, both the user Ui and the grid server can authenticate each other's identities, thereby preventing illegal users from pretending to be identities. The grid user Ui and the grid server can complete the authentication process without resorting to complex bilinear mapping calculations, so the computational overhead is small. The grid user and grid server can complete the authentication process without transmitting the original identification. Therefore, this scheme has the feature of anonymous authentication. In this solution, the authentication process does not require infrastructure such as PKI, so the deployment is simple. Experimental results show that the protocol is feasible in practical applications
Liang, Xiao, An, Ningyu, Li, Da, Zhang, Qiang, Wang, Ruimiao.  2022.  A Blockchain and ABAC Based Data Access Control Scheme in Smart Grid. 2022 International Conference on Blockchain Technology and Information Security (ICBCTIS). :52—55.
In the smart grid, the sharing of power data among various energy entities can make the data play a higher value. However, there may be unauthorized access while sharing data, which makes many entities unwilling to share their data to prevent data leakage. Based on blockchain and ABAC (Attribute-based Access Control) technology, this paper proposes an access control scheme, so that users can achieve fine-grained access control of their data when sharing them. The solution uses smart contract to achieve automated and reliable policy evaluation. IPFS (Interplanetary File System) is used for off-chain distributed storage to share the storage pressure of blockchain and guarantee the reliable storage of data. At the same time, all processes in the system are stored in the blockchain, ensuring the accountability of the system. Finally, the experiment proves the feasibility of the proposed scheme.
Frantti, Tapio, Korkiakoski, Markku.  2022.  Security Controls for Smart Buildings with Shared Space. 2022 6th International Conference on Smart Grid and Smart Cities (ICSGSC). :156—165.
In this paper we consider cyber security requirements of the smart buildings. We identify cyber risks, threats, attack scenarios, security objectives and related security controls. The work was done as a part of a smart building design and construction work. From the controls identified w e concluded security practices for engineering-in smart buildings security. The paper provides an idea toward which system security engineers can strive in the basic design and implementation of the most critical components of the smart buildings. The intent of the concept is to help practitioners to avoid ad hoc approaches in the development of security mechanisms for smart buildings with shared space.
Rashed, Muhammad, Kamruzzaman, Joarder, Gondal, Iqbal, Islam, Syed.  2022.  Vulnerability Assessment framework for a Smart Grid. 2022 4th Global Power, Energy and Communication Conference (GPECOM). :449—454.
The increasing demand for the interconnected IoT based smart grid is facing threats from cyber-attacks due to inherent vulnerability in the smart grid network. There is a pressing need to evaluate and model these vulnerabilities in the network to avoid cascading failures in power systems. In this paper, we propose and evaluate a vulnerability assessment framework based on attack probability for the protection and security of a smart grid. Several factors were taken into consideration such as the probability of attack, propagation of attack from a parent node to child nodes, effectiveness of basic metering system, Kalman estimation and Advanced Metering Infrastructure (AMI). The IEEE-300 bus smart grid was simulated using MATPOWER to study the effectiveness of the proposed framework by injecting false data injection attacks (FDIA); and studying their propagation. Our results show that the use of severity assessment standards such as Common Vulnerability Scoring System (CVSS), AMI measurements and Kalman estimates were very effective for evaluating the vulnerability assessment of smart grid in the presence of FDIA attack scenarios.
Mohammed, Amira, George, Gibin.  2022.  Vulnerabilities and Strategies of Cybersecurity in Smart Grid - Evaluation and Review. 2022 3rd International Conference on Smart Grid and Renewable Energy (SGRE). :1—6.
Smart grid (SG) is considered the next generation of the traditional power grid. It is mainly divided into three main infrastructures: power system, information and communication infrastructures. Cybersecurity is imperative for information infrastructure and the secure, reliable, and efficient operation of the smart grid. Cybersecurity or a lack of proper implementation thereof poses a considerable challenge to the deployment of SG. Therefore, in this paper, A comprehensive survey of cyber security is presented in the smart grid context. Cybersecurity-related information infrastructure is clarified. The impact of adopting cybersecurity on control and management systems has been discussed. Also, the paper highlights the cybersecurity issues and challenges associated with the control decisions in the smart grid.
Feng, Guocong, Huang, Qingshui, Deng, Zijie, Zou, Hong, Zhang, Jiafa.  2022.  Research on cloud security construction of power grid in smart era. 2022 IEEE 2nd International Conference on Data Science and Computer Application (ICDSCA). :976—980.
With the gradual construction and implementation of cloud computing, the information security problem of the smart grid has surfaced. Therefore, in the construction of the smart grid cloud computing platform, information security needs to be considered in planning, infrastructure, and management at the same time, and it is imminent to build an information network that is secure from terminal to the platform to data. This paper introduces the concept of cloud security technology and the latest development of cloud security technology and discusses the main strategies of cloud security construction in electric power enterprises.
Fan, Jinqiang, Xu, Yonggang, Ma, Jing.  2022.  Research on Security Classification and Classification Method of Power Grid Data. 2022 6th International Conference on Smart Grid and Smart Cities (ICSGSC). :72—76.
In order to solve the problem of untargeted data security grading methods in the process of power grid data governance, this paper analyzes the mainstream data security grading standards at home and abroad, investigates and sorts out the characteristics of power grid data security grading requirements, and proposes a method that considers national, social, and A grid data security classification scheme for the security impact of four dimensions of individuals and enterprises. The plan determines the principle of power grid data security classification. Based on the basic idea of “who will be affected to what extent and to what extent when the power grid data security is damaged”, it defines three classification factors that need to be considered: the degree of impact, the scope of influence, and the objects of influence, and the power grid data is divided into five security levels. In the operation stage of power grid data security grading, this paper sorts out the experience and gives the recommended grading process. This scheme basically conforms to the status quo of power grid data classification, and lays the foundation for power grid data governance.
Li, Guang-ye, Zhang, Jia-xin, Wen, Xin, Xu, Lang-Ming, Yuan, Ying.  2022.  Construction of Power Forecasting and Environmental Protection Data Platform Based on Smart Grid Big Data. 2022 International Conference on Applied Artificial Intelligence and Computing (ICAAIC). :801—804.
In today's era, the smart grid is the carrier of the new energy technology revolution and a very critical development stage for grid intelligence. In the process of smart grid operation, maintenance and maintenance, many heterogeneous and polymorphic data can be formed, that is to say big data. This paper analyzes the power big data prediction technology for smart grid applications, and proposes practical application strategies In this paper, an in-depth analysis of the relationship between cloud computing and big data key technologies and smart grid is carried out, and an overview of the key technologies of electric power big data is carried out.
Yao, Jiming, Wu, Peng, Chen, Duanyun, Wang, Wei, Fang, Youxu.  2022.  A security scheme for network slicing selection based on Pohlig-Hellman algorithm in smart grid. 2022 IEEE 10th Joint International Information Technology and Artificial Intelligence Conference (ITAIC). 10:906—910.
5G has significantly facilitated the development of attractive applications such as autonomous driving and telemedicine due to its lower latency, higher data rates, and enormous connectivity. However, there are still some security and privacy issues in 5G, such as network slicing privacy and flexibility and efficiency of network slicing selection. In the smart grid scenario, this paper proposes a 5G slice selection security scheme based on the Pohlig-Hellman algorithm, which realizes the protection of slice selection privacy data between User i(Ui) and Access and Mobility Management function (AMF), so that the data will not be exposed to third-party attackers. Compared with other schemes, the scheme proposed in this paper is simple in deployment, low in computational overhead, and simple in process, and does not require the help of PKI system. The security analysis also verifies that the scheme can accurately protect the slice selection privacy data between Ui and AMF.
Joshi, Sanskruti, Li, Ruixiao, Bhattacharjee, Shameek, Das, Sajal K., Yamana, Hayato.  2022.  Privacy-Preserving Data Falsification Detection in Smart Grids using Elliptic Curve Cryptography and Homomorphic Encryption. 2022 IEEE International Conference on Smart Computing (SMARTCOMP). :229—234.
In an advanced metering infrastructure (AMI), the electric utility collects power consumption data from smart meters to improve energy optimization and provides detailed information on power consumption to electric utility customers. However, AMI is vulnerable to data falsification attacks, which organized adversaries can launch. Such attacks can be detected by analyzing customers' fine-grained power consumption data; however, analyzing customers' private data violates the customers' privacy. Although homomorphic encryption-based schemes have been proposed to tackle the problem, the disadvantage is a long execution time. This paper proposes a new privacy-preserving data falsification detection scheme to shorten the execution time. We adopt elliptic curve cryptography (ECC) based on homomorphic encryption (HE) without revealing customer power consumption data. HE is a form of encryption that permits users to perform computations on the encrypted data without decryption. Through ECC, we can achieve light computation. Our experimental evaluation showed that our proposed scheme successfully achieved 18 times faster than the CKKS scheme, a common HE scheme.
Feng, Guocong, Mu, Tianshi, Lyu, Huahui, Yang, Hang, Lai, Yuyang, Li, Huijuan.  2022.  A Lightweight Attribute-based Encryption Scheme for Data Access Control in Smart Grids. 2022 IEEE 5th International Conference on Computer and Communication Engineering Technology (CCET). :280—284.
Smart grids are envisioned as the next-generation electricity grids. The data measured from the smart grid is very sensitive. It is thus highly necessary to adopt data access control in smart grids to guarantee the security and privacy of the measured data. Due to its flexibility and scalability, attribute-based encryption (ABE) is widely utilized to realize data access control in smart grids. However, most existing ABE solutions impose a heavy decryption overhead on their users. To this end, we propose a lightweight attribute-based encryption scheme for data access control in smart grids by adopting the idea of computation outsourcing. Under our proposed scheme, users can outsource a large amount of computation to a server during the decryption phase while still guaranteeing the security and privacy of the data. Theoretical analysis and experimental evaluation demonstrate that our scheme outperforms the existing schemes by achieving a very low decryption cost.
Wang, Wei, Yao, Jiming, Shao, Weiping, Xu, Yangzhou, Peng, Shaowu.  2022.  Efficient 5G Network Slicing Selection with Privacy in Smart Grid. 2022 IEEE 10th Joint International Information Technology and Artificial Intelligence Conference (ITAIC). 10:916—922.
To fulfill different requirements from various services, the smart grid typically uses 5G network slicing technique for splitting the physical network into multiple virtual logical networks. By doing so, end users in smart grid can select appropriate slice that is suitable for their services. Privacy has vital significance in network slicing selection, since both the end user and the network entities are afraid that their sensitive slicing features are leaked to an adversary. At the same time, in the smart grid, there are many low-power users who are not suitable for complex security schemes. Therefore, both security and efficiency are basic requirements for 5G slicing selection schemes. Considering both security and efficiency, we propose a 5G slicing selection security scheme based on matching degree estimation, called SS-MDE. In SS-MDE, a set of random numbers is used to hide the feature information of the end user and the AMF which can provide privacy protection for exchanged slicing features. Moreover, the best matching slice is selected by calculating the Euclid distance between two slices. Since the algorithms used in SS-MDE include only several simple mathematical operations, which are quite lightweight, SS-MDE can achieve high efficiency. At the same time, since third-party attackers cannot extract the slicing information, SS-MDE can fulfill security requirements. Experimental results show that the proposed scheme is feasible in real world applications.
Choudhary, Sachin, Kumar, Abhimanyu, Kumar, Krishan.  2022.  An Efficient Key Agreement Protocol for Smart Grid communication. 2022 2nd International Conference on Emerging Frontiers in Electrical and Electronic Technologies (ICEFEET). :1—5.
Integration of technology with power grid emerged Smart grid. The advancement of power grid into smart grid faces some security issues like message mod-ification attacks, message injection attacks etc. If these issues are correctly not addressed, then the performance of the smart grid is degraded. Smart grid has bidirectional communication among the smart grid entities. The flow of user energy consumption information between all smart grid entities may lead the user privacy violation. Smart grids have various components but service providers and smart meters are the main components. Smart meters have sensing and communication functionality, while service providers have control and communication functionality. There are many privacy preservation schemes proposed that ensure the cus-tomer's privacy in the smart grid. To preserve the customer's data privacy and communication, authentication and key agreement schemes are required between the smart meter and the service provider. This paper proposes an efficient key agreement protocol to handle several security challenges in smart grid. The proposed protocol is tested against the various security attributes necessary for a key establishment protocol and found safe. Further the performance of the proposed work is compared with several others existing work for smart grid application and it has been observed that the proposed protocol performs significantly better than the existing protocols available in the literature.
Li, Ruixiao, Bhattacharjee, Shameek, Das, Sajal K., Yamana, Hayato.  2022.  Look-Up Table based FHE System for Privacy Preserving Anomaly Detection in Smart Grids. 2022 IEEE International Conference on Smart Computing (SMARTCOMP). :108—115.
In advanced metering infrastructure (AMI), the customers' power consumption data is considered private but needs to be revealed to data-driven attack detection frameworks. In this paper, we present a system for privacy-preserving anomaly-based data falsification attack detection over fully homomorphic encrypted (FHE) data, which enables computations required for the attack detection over encrypted individual customer smart meter's data. Specifically, we propose a homomorphic look-up table (LUT) based FHE approach that supports privacy preserving anomaly detection between the utility, customer, and multiple partied providing security services. In the LUTs, the data pairs of input and output values for each function required by the anomaly detection framework are stored to enable arbitrary arithmetic calculations over FHE. Furthermore, we adopt a private information retrieval (PIR) approach with FHE to enable approximate search with LUTs, which reduces the execution time of the attack detection service while protecting private information. Besides, we show that by adjusting the significant digits of inputs and outputs in our LUT, we can control the detection accuracy and execution time of the attack detection, even while using FHE. Our experiments confirmed that our proposed method is able to detect the injection of false power consumption in the range of 11–17 secs of execution time, depending on detection accuracy.
Ma, Youjie, Su, Hua, Zhou, Xuesong, Tu, Fuhou.  2022.  Research on Data Security and Privacy Protection of Smart Grid Based on Alliance Chain. 2022 IEEE International Conference on Mechatronics and Automation (ICMA). :157—162.
As a new generation of power grid system, smart grid and smart meter conduct two-way communication to realize the intelligent collection, monitoring and dispatching of user power data, so as to achieve a safer, stable, reliable and efficient power grid environment. With the vigorous development of power grid, there are also some security and privacy problems. This paper uses Paillier homomorphic encryption algorithm and role-based access control strategy to ensure the privacy security in the process of multi-dimensional aggregation, data transmission and sharing of power data. Applying the characteristics of blockchain technology such as decentralization, non tampering and traceability to the smart grid can effectively solve the privacy and security problems of power data transmission and sharing in the smart grid. This paper compares Paillier encryption algorithm with PPAR algorithm and SIAHE algorithm in terms of encryption mechanism, number of aggregators and computational complexity respectively. The results show that Paillier homomorphic encryption algorithm has higher data privacy and security.
Wang, Mei.  2022.  Big Data Analysis and Mining Technology of Smart Grid Based on Privacy Protection. 2022 6th International Conference on Computing Methodologies and Communication (ICCMC). :868—871.
Aiming at the big data security and privacy protection issues in the smart grid, the current key technologies for big data security and privacy protection in smart grids are sorted out, and a privacy-protecting smart grid association rule is proposed according to the privacy-protecting smart grid big data analysis and mining technology route The mining plan specifically analyzes the risk factors in the operation of the new power grid, and discusses the information security of power grid users from the perspective of the user, focusing on the protection of privacy and security, using safe multi-party calculation of the support and confidence of the association rules. Privacy-protecting smart grid big data mining enables power companies to improve service quality to 7.5% without divulging customer private information.
Clausen, Marie, Schütz, Johann.  2022.  Identifying Security Requirements for Smart Grid Components: A Smart Grid Security Metric. 2022 IEEE 20th International Conference on Industrial Informatics (INDIN). :208—213.
The most vital requirement for the electric power system as a critical infrastructure is its security of supply. In course of the transition of the electric energy system, however, the security provided by the N-1 principle increasingly reaches its limits. The IT/OT convergence changes the threat structure significantly. New risk factors, that can lead to major blackouts, are added to the existing ones. The problem, however, the cost of security optimizations are not always in proportion to their value. Not every component is equally critical to the energy system, so the question arises, "How secure does my system need to be?". To adress the security-by-design principle, this contribution introduces a Security Metric (SecMet) that can be applied to Smart Grid architectures and its components and deliver an indicator for the "Securitisation Need" based on an individual risk assessment.
Hoque, Mohammad Aminul, Hossain, Mahmud, Hasan, Ragib.  2022.  BenchAV: A Security Benchmarking Framework for Autonomous Driving. 2022 IEEE 19th Annual Consumer Communications & Networking Conference (CCNC). :729—730.
Autonomous vehicles (AVs) are capable of making driving decisions autonomously using multiple sensors and a complex autonomous driving (AD) software. However, AVs introduce numerous unique security challenges that have the potential to create safety consequences on the road. Security mechanisms require a benchmark suite and an evaluation framework to generate comparable results. Unfortunately, AVs lack a proper benchmarking framework to evaluate the attack and defense mechanisms and quantify the safety measures. This paper introduces BenchAV – a security benchmark suite and evaluation framework for AVs to address current limitations and pressing challenges of AD security. The benchmark suite contains 12 security and performance metrics, and an evaluation framework that automates the metric collection process using Carla simulator and Robot Operating System (ROS).
Purdy, Ruben, Duvalsaint, Danielle, Blanton, R. D. Shawn.  2022.  Security Metrics for Logic Circuits. 2022 IEEE International Symposium on Hardware Oriented Security and Trust (HOST). :53—56.
Any type of engineered design requires metrics for trading off both desirable and undesirable properties. For integrated circuits, typical properties include circuit size, performance, power, etc., where for example, performance is a desirable property and power consumption is not. Security metrics, on the other hand, are extremely difficult to develop because there are active adversaries that intend to compromise the protected circuitry. This implies metric values may not be static quantities, but instead are measures that degrade depending on attack effectiveness. In order to deal with this dynamic aspect of a security metric, a general attack model is proposed that enables the effectiveness of various security approaches to be directly compared in the context of an attack. Here, we describe, define and demonstrate that the metrics presented are both meaningful and measurable.
Benarous, Leila, Boudjit, Saadi.  2022.  Security and Privacy Evaluation Methods and Metrics in Vehicular Networks. 2022 IEEE 19th Annual Consumer Communications & Networking Conference (CCNC). :1—6.
The vehicular networks extend the internet services to road edge. They allow users to stay connected offering them a set of safety and infotainment services like weather forecasts and road conditions. The security and privacy are essential issues in computing systems and networks. They are particularly important in vehicular networks due to their direct impact on the users’ safety on road. Various researchers have concentrated their efforts on resolving these two issues in vehicular networks. A great number of researches are found in literature and with still existing open issues and security risks to be solved, the research is continuous in this area. However, the researchers may face some difficulties in choosing the correct method to prove their works or to illustrate their excellency in comparison with existing solutions. In this paper, we review a set of evaluation methodologies and metrics to measure, proof or analyze privacy and security solutions. The aim of this review is to illuminate the readers about the possible existing methods to help them choose the correct techniques to use and reduce their difficulties.
Kareem, Husam, Almousa, Khaleel, Dunaev, Dmitriy.  2022.  Matlab GUI-based Tool to Determine Performance Metrics of Physical Unclonable Functions. 2022 Cybernetics & Informatics (K&I). :1—5.
This paper presents a MATLAB Graphical User Interface (GUI) based tool that determines the performance evaluation metrics of the physically unclonable functions (PUFs). The PUFs are hardware security primitives which can be utilized in several hardware security applications like integrated circuits protection, device authentication, secret key generation, and hardware obfuscation. Like any other technology approach, PUFs evaluation requires testing different performance metrics, each of which can be determined by at least one mathematical equation. The proposed tool (PUFs Tool) reads the PUF instances’ output and then computes and generates the values of the main PUFs’ performance metrics: uniqueness, reliability, uniformity, and bit-aliasing. In addition, it generates a bar code for each PUF instance considered in the evaluation process. The PUFs Tool is designed and developed using the app designer of MATLAB software 2021b.
Masago, Hitoshi, Nodaka, Hiro, Kishimoto, Kazuma, Kawai, Alaric Yohei, Shoji, Shuichi, Mizuno, Jun.  2022.  Nano-Artifact Metrics Chip Mounting Technology for Edge AI Device Security. 2022 17th International Microsystems, Packaging, Assembly and Circuits Technology Conference (IMPACT). :1—4.
In this study, the effect of surface treatment on the boding strength between Quad flat package (QFP) and quartz was investigated for establishing a QFP/quartz glass bonding technique. This bonding technique is necessary to prevent bond failure at the nano-artifact metrics (NAM) chip and adhesive interface against physical attacks such as counterfeiting and tampering of edge AI devices that use NAM chips. Therefore, we investigated the relationship between surface roughness and tensile strength by applying surface treatments such as vacuum ultraviolet (VUV) and Ar/O2 plasma. All QFP/quartz glass with surface treatments such as VUV and Ar/O2 plasma showed increased bond strength. Surface treatment and bonding technology for QFP and quartz glass were established to realize NAM chip mounting.
Kappelhoff, Fynn, Rasche, Rasmus, Mukhopadhyay, Debdeep, Rührmair, Ulrich.  2022.  Strong PUF Security Metrics: Response Sensitivity to Small Challenge Perturbations. 2022 23rd International Symposium on Quality Electronic Design (ISQED). :1—10.
This paper belongs to a sequence of manuscripts that discuss generic and easy-to-apply security metrics for Strong PUFs. These metrics cannot and shall not fully replace in-depth machine learning (ML) studies in the security assessment of Strong PUF candidates. But they can complement the latter, serve in initial PUF complexity analyses, and are much easier and more efficient to apply: They do not require detailed knowledge of various ML methods, substantial computation times, or the availability of an internal parametric model of the studied PUF. Our metrics also can be standardized particularly easily. This avoids the sometimes inconclusive or contradictory findings of existing ML-based security test, which may result from the usage of different or non-optimized ML algorithms and hyperparameters, differing hardware resources, or varying numbers of challenge-response pairs in the training phase.This first manuscript within the abovementioned sequence treats one of the conceptually most straightforward security metrics on that path: It investigates the effects that small perturbations in the PUF-challenges have on the resulting PUF-responses. We first develop and implement several sub-metrics that realize this approach in practice. We then empirically show that these metrics have surprising predictive power, and compare our obtained test scores with the known real-world security of several popular Strong PUF designs. The latter include (XOR) Arbiter PUFs, Feed-Forward Arbiter PUFs, and (XOR) Bistable Ring PUFs. Along the way, our manuscript also suggests techniques for representing the results of our metrics graphically, and for interpreting them in a meaningful manner.
Wu, Haijiang.  2022.  Effective Metrics Modeling of Big Data Technology in Electric Power Information Security. 2022 6th International Conference on Computing Methodologies and Communication (ICCMC). :607—610.
This article focuses on analyzing the application characteristics of electric power big data, determining the advantages that electric power big data provides to the development of enterprises, and expounding the power information security protection technology and management measures under the background of big data. Focus on the protection of power information security, and fundamentally control the information security control issues of power enterprises. Then analyzed the types of big data structure and effective measurement modeling, and finally combined with the application status of big data concepts in the construction of electric power information networks, and proposed optimization strategies, aiming to promote the effectiveness of big data concepts in power information network management activities. Applying the creation conditions, the results show that the measurement model is improved by 7.8%
Yee, George O. M..  2022.  Improving the Derivation of Sound Security Metrics. 2022 IEEE 46th Annual Computers, Software, and Applications Conference (COMPSAC). :1804—1809.
We continue to tackle the problem of poorly defined security metrics by building on and improving our previous work on designing sound security metrics. We reformulate the previous method into a set of conditions that are clearer and more widely applicable for deriving sound security metrics. We also modify and enhance some concepts that led to an unforeseen weakness in the previous method that was subsequently found by users, thereby eliminating this weakness from the conditions. We present examples showing how the conditions can be used to obtain sound security metrics. To demonstrate the conditions' versatility, we apply them to show that an aggregate security metric made up of sound security metrics is also sound. This is useful where the use of an aggregate measure may be preferred, to more easily understand the security of a system.