Security Margin Research Articles

Automated enumeration of block cipher differentials: An optimized branch-and-bound GPU framework

Block ciphers are prevalent in various security protocols used daily such as TLS, OpenPGP, and SSH. Their primary purpose is the protection of user data, both in transit and at rest. One of the de facto methods to evaluate block cipher security is differential cryptanalysis. Differential cryptanalysis observes the propagation of input patterns (input differences) through the cipher to produce output patterns (output differences). This probabilistic propagation is known as a differential; the identification of which is a measure of a block cipher’s security margins. This paper introduces an optimized GPU-based branch-and-bound framework for differential search. We optimize search efficiency by parallelizing all branch-and-bound operations, completing the entire search on the GPU without communicating with the CPU. The meet-in-the-middle (MITM) approach is also adopted for further performance gains. We analyze the financial and computational costs of the proposed framework using Google Cloud VM to showcase its practicality. When optimized for performance, we can attain up to 90x speedup while saving up to 47% of the running cost as compared to a single CPU core. When optimized for cost, the proposed framework can save up to 83% of financial costs while retaining a speedup of up to 40x. As a proof of concept, the proposed framework was then applied on 128-bit TRIFLE-BC, 64-bit PRESENT, and 64-bit GIFT. Notably, we identified the best differentials for PRESENT (16 rounds) and 64-bit GIFT (13 rounds) to date, with estimated probabilities of 2−61.7964 and 2−60.66 respectively. Although the differential results for TRIFLE-BC were incremental, the proposed framework was able to construct differentials for 43 rounds that consisted of approximately 5.8x more individual trails than previous work, making it one of the most efficient approaches for larger block ciphers.

Exclusive surgical treatment of a primary cutaneous marginal zone lymphoma: a case report

Primary cutaneous B-cell lymphomas are non-Hodgkin lymphomas presenting only in the skin and represent 25% of all primary cutaneous lymphomas. Based on their clinical behavior, they are classified into indolent and intermediate forms. Treatment of indolent forms includes surgery, radiotherapy, and, in extensive disease, rituximab. We report a case of a 57-year-old woman with a single nodule in the left arm treated with surgical excision with 5-mm security margins, without relapse after 36 months. Surgery is a therapeutic option in these lymphomas without compromising disease-free survival.

Smart deployment of energy storage and renewable energy sources for improving distribution system efficacy

<abstract><p>Climate change, global warming, the depletion of fossil fuels, and rising energy demand are the main forces behind the increase in renewable energy sources. However, the unpredictability of power output from these renewable energy sources presents distribution system integration issues such as limited feeder capacity, unstable voltage, and network power loss. This study analyses the African vulture optimisation algorithm to determine the best allocation of distribution generators, with an emphasis on reducing the ageing of distribution transformers and delaying investment in feeders. The optimization technique provides faster global convergence and outperforms existing bio-inspired algorithms verified with benchmark uni-modal functions as a result of a larger crossover between the exploration and exploitation phases. The key aim is to decrease active power loss while simultaneously enhancing security margin and voltage stability. The IEEE 69-bus RDS system is utilised to validate the case studies for appropriate allocation of photovoltaic, wind turbine generation, and battery energy storage systems units, as well as offering the ideal energy management approach. During simulation, uncertainty on the characteristics of renewable energy source is accounted for. The results demonstrate the efficacy of the proposed algorithm with a substantial improvement in voltage profile, the benefit of lower CO2 emissions, an increase in security margin of up to 143%, and the advantage of extending the feeder investment deferral period by more than 50 years. In addition, the distribution transformer ageing acceleration factor improves significantly in the case of an increase in load demand.</p></abstract>

Comparative Study on DES and Triple DES Algorithms and Proposal of a New Algorithm Named Ternary DES for Digital Payments

Whenever new algorithms are designed intruders try to break the key with the help of attack models. No algorithm is perfect against all attacks. But DES irrespective of its small key size, it has been considered to be strong design cipher till today. Designers of DES guaranteed a security margin of 2 power 56. If any attack which is essentially better than 2 power 56 search then that considered to be attack. To crack DES attackers need to spend $ 220000 so that the key can be revealed in 56 hours. But for digital transactions if the key can expire for less than 5 minutes it‟s difficult to crack. If this is the case with DES then it will be much more difficult to break Triple DES, which uses 112 bits of key size. The problem with Triple DES is having more rounds, which takes more processing time and space. Not only cryptography, even Light Weight Cryptography needs low processing time and space. Hence a new algorithm named ternary DES is proposed which requires only 56-bit key and 16 rounds. Ternary DES has the advantage of DES with the same key space and number of rounds, and advantage of Triple DES with difficult to break. To propose new algorithms for solving security issues many constraints we need to take into account. With one algorithm we can solve one or a few issues but not all.

Cyber-Physical Coordinated Risk Mitigation in Smart Grids Based on Attack-Defense Game

Since modern smart grids have various and deeply coupled cyber-physical components, they are vulnerable to malicious cyber attacks. Although regular defenses including firewall and IDS are deployed, they may be weakened by zero-day vulnerabilities and sophisticated attack schemes. Therefore, defense strategies to mitigate the risk of blackouts during cyber attacks are necessary. This paper proposes a cyber-physical coordinated defense strategy to overcome the disruption and minimize the risk as much as possible. At the cyber layer, a zero-sum multilevel Markovian Stackelberg game is proposed to model sequential actions of the attacker and the defender. The defender distributes defensive resources to protect lines in a real-time manner, according to the attacker's action. If cyber attacks should result in physical outages, defense at the physical layer is then employed. A security-constrained optimal power flow reserving security margin of critical components will be performed to minimize the blackout scale and potential future risk. To solve the corresponding optimization problem and further get the optimal defense strategy, this paper devises a novel “water-pouring” algorithm. Lastly, test results show that the proposed dynamic defense strategy mitigates risk significantly and outperforms existing methods.

Integral Cryptanalysis of Lightweight Block Cipher PIPO

PIPO is a lightweight block cipher proposed at ICISC 2020, which has a byte-oriented structure suitable for bit-sliced implementation and allows for efficient higher-order masking implementations. In this study, we use bit-based division property techniques to construct 6-round integral distinguishers, and propose key-recovery attacks on 8 rounds of PIPO-64/128 and 10 rounds of PIPO-64/256. The data complexity of both attacks is 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">63</sup> chosen plaintexts and the time complexities are 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">125</sup> and 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">253.8</sup> respectively. Our results complement the security analysis of PIPO, and show that the PIPO structure is resistant to recently researched cryptanalysis methods. Because only differential and linear attacks were carefully considered to determine the number of rounds of PIPO, our work, based on division property, is important for verifying the security margin.

Eight-Day Methotrexate/Folinic Acid Regime as Single Agent Chemotherapy for Low-Risk Gestational Trophoblastic Neoplasia: A Retrospective Study

Objective: To evaluate the 8-day methotrexate (MTX)/folinic acid (FA) as a first-line chemotherapy regimen treatment in terms of complete regression of disease in women with low-risk gestational trophoblastic neoplasia (GTN). Material and Methods: All patients with low-risk GTN treated with an 8-day MTX/FA regimen were retrospectively included in the study. International Federation of Obstetrics and Gynecology and the modified World Health Organization Prognostic Scoring System were used to classify the risk of GTN. All women received diagnostic imaging evaluation before starting the treatment. The same MTX/FA regime was used repeating as a two-week cycle until normalization of the beta-human chorionic gonadotropin (ß-HCG), thus monthly ß-HCG follow-up was scheduled for up to 1 year. Results: Successful treatment was achieved in 56/66 (84.8%) patients. Nine (13.6%) women had resistance and 1 (1.6%) toxicity. The resistance patients were successfully treated with EMA-CO (etoposide, methotrexate, actinomycin D, cyclophosphamide, vincristine) protocol, whereas the patient who showed toxicity to the MTX/FA regime was successfully treated with actinomycin-D. Conclusion: Eight-day MTX/FA regime could be useful in low-risk GTN patients with good security margins. The toxicity rates in this protocol were determined as quite low. All resistance was treated successfully with the EMA-CO protocol.

Intelligent stability margin improvement using series and shunt controllers

Electric market always prefers to use full capacity of existing power system to control the costs. Flexible alternate current transmission system (FACTS) devices introduced by Electric Power Research Institute (EPRI) to increase the usable capacity of power system. Placement of FACTS controllers in power system is a critical issue to reach their maximum advantages. This article focused on the application of FACTS devices to increase the stability of power system using artificial intelligence. Five types of series and shunt FACTS controllers are considered in this study. Continuation power flow (CPF) analysis used to calculate the collapse point of power systems. Controlling parameters of FACTS devices including their locations are determined using real number representation based genetic algorithm (RNRGA) in order to improve the secure margin of operating condition of power system. The 14 and 118 buses IEEE standard test systems are utilized to verify the recommended method. The achieved results manifestly proved the effectiveness of proposed intelligent method to increase the stability of power system by determining the optimum location and size of each type of FACTS devices.

Representing Uncertainty in Physical Security Risk Assessment

The importance of (physical) security is increasingly acknowledged by society and the scientific community. In light of increasing terrorist threat levels, numerous security assessments of critical infrastructures are conducted in practice and researchers propose new approaches continuously. While practical security risk assessments (SRA) use mostly qualitative methods, most of the lately proposed approaches are based on quantitative metrics. Due to little evidence of actual attacks, both qualitative and quantitative approaches suffer from the fundamental problem of inherent uncertainties regarding threats and capabilities of security measures as a result from vague data or the usage of expert knowledge. In quantitative analysis, such uncertainties may be represented by, e.g., probability distributions to reflect the knowledge on security measure performance available. This paper focuses on the impact of these uncertainties in security assessment and their consideration in system design. We show this influence by comparing the results of a scalar evaluation that does not take into account uncertainties and another evaluation based on distributed input values. In addition, we show that the influence is concentrated on certain barriers of the security system. Specifically, we discuss the robustness of the system by conducting quantitative vulnerability assessment as part of the SRA process of an airport structure example. Based on these results, we propose the concept of a security margin. This concept accounts for the uncertain knowledge of the input parameters in the design of the security system and minimizes the influence of these uncertainties on the actual system performance. We show how this approach can be used for vulnerability assessment by applying it to the initially assessed configuration of the airport structure. The results of this case study support our assumptions that the security margin can help in targeted uncertainty consideration leading to reduced system vulnerability.

Inflation of wood resources in European forests: The footprints of a big-bang.

The current increase in European forest resources forms a singularity across the globe. Whether this trend will persist, and how biological and economic trends feature it form crucial issues to green economy challenges and C sequestration. The present screening of Forest Europe 2015 statistics explored the features, inertia and limits of this expansion, and its relationships with countries’ development, forest management and trade, intense in this area of the world. Persisting footprint of past demographic pressure on forests was identified, with opposed traces on their area and growing stock density. Steady growing stock (GS) increases, proportional to GS, not density-limited, and sustained by forest area increases, supported the view of an inflationary forest dynamic. Economic development and liberalism fostered both forest exploitation and production, yielding no significant impact on GS changes. Wood exports exerted a tension on forest exploitation and GS changes, thus lowering GS inflation but providing a resource security margin in the face of expected climate threats. Conflicting a common view, GS inflation and moderate felling-to-increment ratios make increased use of wood resources and C sequestration reconcilable, and GS expansion timely for ongoing EU forest policy processes. Anticipated adverse impacts of ongoing climate change were not clearly identified in these statistics.

A cost-effective voltage security constrained congestion management approach for transmission system operation improvement

The escalating energy demand in the power system is known as a significant challenge for planning and expanding the future power system. Investigations have indicated that easing the line capacity of the power system can be an effective and efficient way to overwhelm this issue in the power system. This paper basically concentrates on providing a Transmission Switching (TS) based cost-effective approach to provide minimum voltage security margin (VSM) index while easing the active/reactive power capacity of the transmission lines. Note that this work is not only able to decrease the line loading of the system, but also can lead to a substantial reduction in the operation cost of the power system. However, the TS method can bring a significant challenge when it comes to the switching without imposing any restrictions on the number of switchings in a specific period of time. Considering the fact that the increase of switchings' number triggers the failure of the switches which, in turn, causes the outage of the lines and load interruption, one can conclude that the switch failure profoundly affects the rate of power network's outage. Since the TS method is able to prevent the lines from getting congested, it can improve the stability of the power system and significantly decrease the number of switchings of the lines. In this regard, the congestion management can be considered as an effective tool for improving the power system's stability and loading. This paper basically concentrates on employing the TS approach in the optimal power flow problem with the goal of decreasing the number of switchings of the lines, enhancing the SVM index, improving the loading of the power system and decreasing the operation cost of the system. The effectiveness of the studied model is tested and evaluated on 6-bus and 93-bus networks in GAMS software.

An Online Security Prediction and Control Framework for Modern Power Grids

The proliferation of renewable energy sources distributed generation (RES-DG) into the grid results in time-varying inertia constant. To ensure the security of the grid under varying inertia, techniques for fast security assessment are required. In addition, considering the high penetration of RES-DG units into the modern grids, security prediction using varying grid features is crucial. The computation burden concerns of conventional time-domain security assessment techniques make it unsuitable for real-time security prediction. This paper, therefore, proposes a fast security monitoring model that includes security prediction and load shedding for security control. The attributes considered in this paper include the load level, inertia constant, fault location, and power dispatched from the renewable energy sources generator. An incremental Naïve Bayes algorithm is applied on the training dataset developed from the responses of the grid to transient stability simulations. An additive Gaussian process regression (GPR) model is proposed to estimate the load shedding required for the predicted insecure states. Finally, an algorithm based on the nodes’ security margin is proposed to determine the optimal node (s) for the load shedding. The average security prediction and load shedding estimation model training times are 1.2 s and 3 s, respectively. The result shows that the proposed model can predict the security of the grid, estimate the amount of load shed required, and determine the specific node for load shedding operation.

Deep Learning-Based Adaptive Remedial Action Scheme with Security Margin for Renewable-Dominated Power Grids

The Remedial Action Scheme (RAS) is designed to take corrective actions after detecting predetermined conditions to maintain system transient stability in large interconnected power grids. However, since RAS is usually designed based on a few selected typical operating conditions, it is not optimal in operating conditions that are not considered in the offline design, especially under frequently and dramatically varying operating conditions due to the increasing integration of intermittent renewables. The deep learning-based RAS is proposed to enhance the adaptivity of RAS to varying operating conditions. During the training, a customized loss function is developed to penalize the negative loss and suggest corrective actions with a security margin to avoid triggering under-frequency and over-frequency relays. Simulation results of the reduced United States Western Interconnection system model demonstrate that the proposed deep learning–based RAS can provide optimal corrective actions for unseen operating conditions while maintaining a sufficient security margin.

Impact of static and dynamic load models on security margin estimation methods

The post-contingency loadability limit (PCLL) and the secure operating limit (SOL) are the two main approaches used when computing the security margins of an electric power system. While the SOL is significantly more computationally demanding than the PCLL, it can account for the dynamic response after a disturbance and generally provides a better measure of the security margin. In this study, the difference between these two methods is compared and analyzed for a range of different contingency and load model scenarios. A methodology to allow a fair comparison between the two security margins is developed and tested on a modified version of the Nordic32 test system. The study shows that the SOL can differ significantly from the PCLL, especially when the system has a high penetration of loads with constant power characteristics or a large share of induction motor loads with fast load restoration. The difference between the methods is also tested for different contingencies, where longer fault clearing times are shown to significantly increase the difference between the two margins.

Stochastic optimal transmission Switching: A novel approach to enhance power grid security margins through vulnerability mitigation under renewables uncertainties

In this paper, a stochastic optimal transmission switching (SOTS) model is developed considering the uncertainty of load, wind power and photovoltaic generation, while minimizing the grid vulnerability. Scenario reduction technique is used for alleviating computational burden of the developed SOTS model. A three-step procedure, named the vulnerability-oriented SOTS (VO-SOTS), is proposed to consider the set of critical transmission lines, i.e., lines whose outage imposes the largest load curtailment. Moreover, to control the negative impacts of the uncertainties, conditional value at risk (CVaR) is used as the risk measure. The proposed VO-SOTS model is formulated as a mixed integer non-linear programming optimization problem and solved using GAMS optimization package. Also, the VO-SOTS model is implemented on the IEEE 118-bus, IEEE 300-bus, and large-scale IEEE 2869-bus standard test systems. Simulation results for these cases show that considering the set of critical lines allows the proposed VO-SOTS model to reduce generation costs while effectively minimizing system vulnerability and risk. In addition, it is shown through extensive case studies that switching off a line based on the proposed three-step VO-SOTS does not increase the grid’s exposure to vulnerability, in contrast to the conventional OTS.

Hierarchical Voltage/VAR security boundaries and margin assessments in Multi-HVDC infeed systems

Operational security issues such as a lack of voltage/VAR support and cascading failures triggered by an initial fault present crucial challenges and issues in systems with multiple high-voltage direct current (HVDC) infeeds with both line-commutated converter (LCC) and voltage-source converter (VSC) links. Due to the complexity of the switching strategy for the filter banks in the converter stations, the modeling of the voltage control process inside converter stations is also complex; however, this complexity is not considered in the existing methods, leading to low calculation accuracy. Therefore, this paper proposes an approach based on hierarchical voltage/VAR security boundaries (HVVSBs) and margin assessments for multi-HVDC infeed systems to ensure high calculation accuracy and speed. The voltage/VAR control characteristics of LCC/VSC stations are appropriately formulated by means of a stepwise search method and boundary information, and an HVVSB-based method of dynamic reactive power reserve evaluation is proposed that is suitable for extreme scenarios. Finally, the proposed method is tested in a modified IEEE-118 system to verify its accuracy and effectiveness.

Load Sharing Scheme Incorporating Power Security Margins for Parallel Operation of Voltage Source Inverters

The interconnection of distributed energy resources (DERs) in microgrids (MGs) operating in both islanded and grid-connected modes require coordinated control strategies. DERs are interfaced with voltage source inverters (VSIs) enabling interconnection. This paper proposes a load demand sharing scheme for the parallel operation of VSIs in an islanded voltage source inverter-based microgrid (VSI-MG). The ride-through capability of a heavily loaded VSI-MG, where some of the VSIs are fully loaded due to the occurrence of an event is investigated. In developing analytical equations to model the VSI, the concept of virtual synchronous machines (VSM) is applied to enable the VSI mimic the inertia effect of synchronous machines. A power frame transformation (PFT) that takes the line ratios of the MG network into account is also incorporated to yield satisfactory transient responses of both network frequency and bus voltages in the MG network. A Jacobian-based method is then developed to take into account the operational capacity of each VSI in the VSI-MG. The resulting amendable droop control constrains the VSIs within their power capabilities when an event occurs. Simulation results presented within demonstrate the effectiveness of the proposed procedure which has great potential to facilitate efforts in maintaining system reliability and resiliency.

Biased differential distinguisher – Cryptanalysis of reduced-round SKINNY

SKINNY is a lightweight tweakable block cipher which received a great deal of cryptanalytic attention due to its elegant structure and efficiency. Despite the cryptanalytic efforts the security margins are remaining high. This has led to SKINNY being used as a component of multiple submissions in the NIST Lightweight Competition, an effort to standardize a lightweight AEAD scheme.Inspired by the SKINNY competitions, multiple attacks on it were reported in different settings (e.g. single vs. related-tweakey) using different techniques (impossible differentials, zero-correlation, meet-in-the-middle, etc.). In this paper we revisit some of these attacks, identify issues with several of them, and offer a series of improved attacks which were experimentally verified. Our best attack can attack up to 18 rounds of SKINNY-64 using 260 chosen plaintexts data, 2116 time, and 2112 memory.

Toward Precise Nutrient Value of Feed in Growing Pigs: Effect of Meal Size, Frequency and Dietary Fibre on Nutrient Utilisation.

Simple SummaryFeed costs are the most important in swine production. Precise determination of nutritional values of pig diets can help reducing feed costs by reducing security margins for nutrients and therefore provide a more sustainable swine production. In commercial farms, pigs have free access to feed and eat with no limitation according to their natural behaviour. In contrast, during digestibility trials, pigs are restricted in their daily intake of feed, which is distributed in a limited number of meals. The number of meals per day and the amount of feed consumed daily can affect the digestibility of the nutrients, the transit time and the metabolism. To reduce feed costs, by-products are frequently added to diets. Most by-products are rich in dietary fibre, which are known to have negative effects on digestibility. Enzymes can be supplemented in the diet to counteract the negative aspects of dietary fibre, but their efficiency can vary depending on the number of meals per day and the amount of feed consumed daily.Nutritional values of ingredients have been and still are the subject of many studies to reduce security margins of nutrients when formulating diets to reduce feed cost. In most studies, pigs are fed a limited amount of feed in a limited number of meals that do not represent how pigs are fed in commercial farm conditions. With free access to feed, pigs follow their intrinsic feeding behaviour. Feed intake is regulated by satiety and satiation signals. Reducing the feed intake level or feeding frequency can affect digestibility and transit time and induce metabolic changes. To reduce feed costs, alternative ingredients that are frequently rich in dietary fibre are added to diets. Fibre acts on the digestion process and transit time by decreasing energy density and causing viscosity. Various analyses of fibre can be realised, and the measured fibre fraction can vary. Exogenous enzymes can be added to counteract the effect of fibre, but digestive tract conditions, influenced by meal size and frequency, can affect the efficiency of supplemented enzymes. In conclusion, the frequency and size of the meals can affect the digestibility of nutrients by modulating gastrointestinal tract conditions (pH and transit time), metabolites (glucose and short-chain fatty acids) and hormones (glucagon-like peptide 1 and peptide tyrosine tyrosine).

Intelligent stability margin improvement using series and shunt controllers

Electric market always prefers to use full capacity of existing power system to control the costs. Flexible alternate current transmission system (FACTS) devices introduced by Electric Power Research Institute (EPRI) to increase the usable capacity of power system. Placement of FACTS controllers in power system is a critical issue to reach their maximum advantages. This article focused on the application of FACTS devices to increase the stability of power system using artificial intelligence. Five types of series and shunt FACTS controllers are considered in this study. Continuation power flow (CPF) analysis used to calculate the collapse point of power systems. Controlling parameters of FACTS devices including their locations are determined using real number representation based genetic algorithm (RNRGA) in order to improve the secure margin of operating condition of power system. The 14 and 118 buses IEEE standard test systems are utilized to verify the recommended method. The achieved results manifestly proved the effectiveness of proposed intelligent method to increase the stability of power system by determining the optimum location and size of each type of FACTS devices.