Papers by Muhammad Mustafa
Journal of Information Security and Applications, 2022
The s-box plays the vital role of creating confusion between the ciphertext and secret key in any... more The s-box plays the vital role of creating confusion between the ciphertext and secret key in any cryptosystem, and is the only nonlinear component in many block ciphers. Dynamic s-boxes, as compared to static, improve entropy of the system, hence leading to better resistance against linear and differential attacks. It was shown in [2] that while incorporating dynamic s-boxes in cryptosystems is sufficiently secure, they do not keep non-linearity invariant. This work provides an algorithmic scheme to generate key-dependent dynamic n × n clone s-boxes having the same algebraic properties namely bijection, nonlinearity, the strict avalanche criterion (SAC), the output bits independence criterion (BIC) as of the initial seed s-box. The method is based on group action of symmetric group S n and a subgroup S 2 n respectively on columns and rows of Boolean functions (GF (2 n) → GF (2)) of s-box. Invariance of the bijection, nonlinearity, SAC, and BIC for the generated clone copies is proved. As illustration, examples are provided for n = 8 and n = 4 along with comparison of the algebraic properties of the clone and initial seed s-box. The proposed method is an extension of [3, 4, 5, 6] which involved group action of S 8 only on columns of Boolean functions (GF (2 8) → GF (2)) of s-box. For n = 4, we have used an initial 4 × 4 s-box constructed by Carlisle Adams and Stafford Tavares [7] to generated (4!) 2 clone copies. For n = 8, it can be seen [3, 4, 5, 6] that the number of clone copies that can be constructed by permuting the columns is 8!. For each column permutation, the proposed method enables to generate 8! clone copies by permuting the rows.
Journal of Business Strategies, 1970
This paper investigates the dynamic effects of annual U.S budget deficit as aratio of GDP and lab... more This paper investigates the dynamic effects of annual U.S budget deficit as aratio of GDP and labor productivity-real wage gap on US stock market performance.The sample period runs from 1950 through 2012. The standard cointegration methodologyis appropriately applied. All the aforementioned variables are nonstationaryin levels revealing I(1) behavior. The coefficient of the error-correction term of thevector error-correction model (VECM) has expected negative sign with statisticalsignificance confirming long-run unidirectional causality stemming from the independentvariables to the stock market return. However, the speed of adjustment towardsa long-run equilibrium is slow as reflected in the low numerical coefficientof the error-correction term. The evidences on short-run interactive feedback effectsare also very weak.
Symmetry, 2019
The Advanced Encryption Standard (AES) is widely used in different kinds of security applications... more The Advanced Encryption Standard (AES) is widely used in different kinds of security applications. The substitution box (S-box) is the main component of many modern symmetric encryption ciphers that provides confusion between the secret key and ciphertext. The S-box component that is used in AES is fixed. If we construct this component dynamically, the encryption strength of AES would be greater than before. In this manuscript, we used chaotic logistic map, Mobius transformation and symmetric group S 256 to construct S-box for AES. The idea behind the proposed work is to make supplementary safe S-box. The presented S-box is analyzed for the following analyses: linear approximation probability (LP), nonlinearity (NL), differential approximation probability (DP), strict avalanche criterion (SAC), and bit independence criterion (BIC). The analyses show that the proposed technique is useful in generating high resistance S-box to known attacks.
International Journal of Monetary Economics and Finance, 2017
This paper analyses the effects of stock market turnover and liquidity, as measures of financial ... more This paper analyses the effects of stock market turnover and liquidity, as measures of financial deepening, on stock market returns in selected 19 developed and 21 developing countries over 1988-2014 by implementing Pedroni's panel cointegration methodology and panel vector error-correction models. Stock market turnover contributes more to stock market returns than stock market liquidity in both selected developed and developing economies. However, the results are much weaker for developing countries than for developed countries.
To empirically study the effects of asset utilization, market competition and market distance on ... more To empirically study the effects of asset utilization, market competition and market distance on stock returns of 1961 US public firms of different industry categories over 2001-2015. The heterogeneous panel data set consists of 23,532 (N= 1961*T= 15) observations. Pedroni’s panel co-integration, panel vector errorcorrection model (PVECM), panel dynamic OLS (PDOLS), and panel generalized method of moments (PGMM) are implemented. Both asset utilization and market competition have short-run and long-run positive effects on stock returns. But the effects of market distance are negative. The evidence for convergence toward the long-run equilibrium is very weak. Firms should be strategic to improve asset utilization, be more competitive and expand market distance to maximize stockholders’ wealth.
Pore-water pressure responses are vital in many aspects of slope management, design and monitorin... more Pore-water pressure responses are vital in many aspects of slope management, design and monitoring. Its measurement however, is difficult, expensive and time consuming. Studies on its predictions are lacking. Support vector machines with linear kernel was used here to predict the responses of pore-water pressure to rainfall. Pore-water pressure response data was collected from slope instrumentation program. Support vector machine meta-parameter calibration and model development was carried out using grid search and k-fold cross validation. The mean square error for the model on scaled test data is 0.0015 and the coefficient of determination is 0.9321. Although pore-water pressure response to rainfall is a complex nonlinear process, the use of linear kernel support vector machine can be employed where high accuracy can be sacrificed for computational ease and time.
Multimedia Tools and Applications, 2021
We have proposed a robust, secure and efficient image encryption algorithm based on chaotic maps ... more We have proposed a robust, secure and efficient image encryption algorithm based on chaotic maps and algebraic structure. Nowadays, the chaotic cryptosystems gained more attention due to their efficiency, the assurance of robustness and high sensitivity corresponding to initial conditions. In literature, there are many encryption algorithms that can simply guarantees security while the schemes based on chaotic systems only promises the uncertainty, both of them can not encounter the needs of current scenario. To tackle this issue, this article proposed an image encryption algorithm based on Lorenz chaotic system and primitive irreducible polynomial substitution box. First, we have proposed 16 different S-boxes based on projective general linear group and 16 primitive irreducible polynomials of Galois field of order 256, and then utilized these S-boxes with combination of chaotic map in image encryption scheme. Three chaotic sequences can be produced by the disturbed of Lorenz chaoti...
Membranes, 2020
In this article, poly(ethylene oxide)-based polymer electrolyte films doped with ammonium iodide ... more In this article, poly(ethylene oxide)-based polymer electrolyte films doped with ammonium iodide (NH4I) and plasticized with glycerol were provided by a solution casting method. In the unplasticized system, the maximum ionic conductivity of 3.96 × 10 − 5 S cm−1 was achieved by the electrolyte comprised of 70 wt. % PEO:30 wt. % NH4I. The conductivity was further enhanced up to ( 1.77 × 10 − 4 S cm−1) for the plasticized system when 10 wt. % glycerol was added to the highest conducting unplasticized one at ambient temperature. The films were characterized by various techniques to evaluate their electrochemical performance. The results of impedance spectroscopy revealed that bulk resistance (Rb) considerably decreased for the highest plasticized polymer electrolyte. The dielectric properties and electric modulus parameters were studied in detail. The LSV analysis verified that the plasticized system can be used in energy storage devices with electrochemical stability up to 1.09 V a...
Asymptotic Analysis, 2016
In this paper we consider a plate equation with internal feedback and viscoelastic damping locali... more In this paper we consider a plate equation with internal feedback and viscoelastic damping localized on a part of the boundary. Without imposing restrictive assumptions on the time-dependent frictional damping, we establish an explicit and general decay rate result that allows a wider class of relaxation functions and generalizes previous results existing in the literature.
This paper reexamines the effects of bilateral nominal exchange rate changes on U.S. bilateral no... more This paper reexamines the effects of bilateral nominal exchange rate changes on U.S. bilateral nominal trade balances with India, Japan, Malaysia, South Korea and Thailand using monthly data from January 1985 through May 2005. The unit root tests, Johansen-Juselius cointegration procedure and the error-correction model are implemented. Each variable is nonstationary in level depicting I (1) behavior. Either λ trace or λ max test confirms cointegrating relationship between the above variables. There is evidence of long-run unidirectional causal flow from exchange rate changes to the changes in U.S. trade balance with each country with short-run interactive feedback relationships. Impulse response analysis exhibits no evidence to support the J-Curve hypothesis excepting Japan. INTRODUCTION This paper re-explores the dynamic causal relationships between the U.S. bilateral nominal trade balance with India, Japan, Malaysia, S. Korea and Thailand, and the bilateral nominal exchange rates using monthly data from January, 1985 through May, 2005. This issue is of increasing importance for the U.S.A. because, since 1981, its annual trade deficit has been consistently escalating (Krugman and Baldurin 1987). The recent fall of U.S. dollar against other major currencies during 2007 also sparks renewed interest in this topic. The U.S.A. pursues freer trade policy and in large measures allows its exchange rate to be determined by the market forces. Though a strong dollar is its declared policy, a weak dollar benefits it by promoting exports and reducing imports. However, these do not happen instantaneously. For example, the weak dollar provides protection to the ailing U.S. auto industry neutralizing the demand for trade restrictions and subsidy. Asia, in general, has been a major destination for U.S. exports. The above countries have been selected because of their strong and enhancing trade relationships with the U.S.A. These countries experienced robust economic growth throughout 1980s and 1990s excepting a brief period after 1997-98 Southeast Asian financial crisis. However, Japan was a notable exception because it went through a prolonged recession from 1988 until 2001.
In this paper, we consider a thermoelastic system with an internal distributed delay. We use the ... more In this paper, we consider a thermoelastic system with an internal distributed delay. We use the energy method to prove, under a suitable assumption on the weight of the delay, that the damping effect through heat conduction is strong enough to uniformly stabilize the system even in the presence of time delay.
Zeitschrift für angewandte Mathematik und Physik, 2012
In this article we consider an n-dimentional thermoelastic system with a viscoelastic damping loc... more In this article we consider an n-dimentional thermoelastic system with a viscoelastic damping localized on a part of the boundary. We establish an explicit and general decay rate result that allows a larger class of relaxation functions and generalizes previous results existing in the literature.
Research Journal of Economics Business and Ict, Dec 15, 2013
Arabian Journal of Mathematics, 2021
We study the following wave equation $$u_{tt}-\Delta u+\alpha (t)\left| u_{t}\right| ^{m(\cdot )-... more We study the following wave equation $$u_{tt}-\Delta u+\alpha (t)\left| u_{t}\right| ^{m(\cdot )-2}u_{t}=0$$ u tt - Δ u + α ( t ) u t m ( · ) - 2 u t = 0 with a nonlinear damping having a variable exponent m(x) and a time-dependent coefficient $$\alpha (t)$$ α ( t ) . We use the multiplier method to establish energy decay results depending on both m and $$\alpha $$ α . We also give four numerical tests to illustrate our theoretical results using the conservative Lax–Wendroff method scheme.
Nonlinear Analysis: Theory, Methods & Applications, 2010
In this paper we consider a viscoelastic equation with a nonlinear feedback localized on a part o... more In this paper we consider a viscoelastic equation with a nonlinear feedback localized on a part of the boundary. We establish an explicit and general decay rate result, using some properties of the convex functions. Our result is obtained without imposing any restrictive growth assumption on the damping term and strongly weakening the usual assumptions on the relaxation function.
Nonlinear Differential Equations and Applications NoDEA, 2008
In this paper we consider Timoshenko systems with either internal or boundary feedbacks. We estab... more In this paper we consider Timoshenko systems with either internal or boundary feedbacks. We establish explicit and generalized decay results, without imposing restrictive growth assumption near the origin on the damping terms.
Electronic Journal of Differential Equations, 2012
Abstract. In this article, we consider a thermoelastic system of type III with a viscoelastic dam... more Abstract. In this article, we consider a thermoelastic system of type III with a viscoelastic damping and internal delay. We use the multiplier method to prove, under suitable assumptions, general energy decay results from which the exponential and polynomial types of decay are only special cases.
Journal of the Franklin Institute, 2007
Latin American Applied Research - An international journal, 2021
Naturally God gifted medicinal plants which contain more potentially active compounds their chara... more Naturally God gifted medicinal plants which contain more potentially active compounds their characterization and isolation are very important and can provide us a great help in making new drugs to cure many diseases. Our current attempt was made to obtain the ethanolic extracts of medicinal plant Cerastium fontanum using a hot continuous soxhlet process and also via maceration method. The concentrated dried fraction extracts of Cerastium fontanum such as aqueous, n-hexane, ethyl acetate and dichloromethane were achieved using liquid-liquid extraction which were then evaluated for in vitro antioxidants potential using DPPH (1,1-diphenyl-2-picryl-hydrazyl) assay and also agar-well diffusion method were used for antimicrobial potential. In vitro antioxidants inhibition potential were measured through spectrophotometer at various concentration (500 to 62.5µg/mL) prepared in standard solvent. Among all extracts aqueous fraction showed IC50 = 2.9 ± 0.05mg/mL maximum potency towards stable...
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Papers by Muhammad Mustafa