Search for: lyapunov-methods
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    Impossible differential cryptanalysis of safer++

    , Article 2008 International Conference on Security and Management, SAM 2008, Las Vegas, NV, 14 July 2008 through 17 July 2008 ; July , 2008 , Pages 10-14 ; 160132085X (ISBN); 9781601320858 (ISBN) Bahrak, B ; Eghlidos, T ; Aref, M. R ; Sharif University of Technology
    In this paper, we describe an impossible differential property for 2.5 rounds of Safer++. It allows an impossible differential attack on 4 rounds of Safer++. The proposed attack requires 2 23 chosen plaintexts and 2 75 bytes of memory and performs 2 84 4-round Safer++ encryptions. The method developed to attack Safer++ can be applied to other block ciphers in Safer family. 1  

    Population capacity threats to urban area resiliency: Observations on chaotic transportation network behavior

    , Article Scientia Iranica ; Volume 23, Issue 4 , 2016 , Pages 1675-1688 ; 10263098 (ISSN) Sharifi, M. S ; Shahabi, M ; Abshar, E ; Khorgami, M. H ; Pourzahedy, H ; Sharif University of Technology
    Sharif University of Technology 
    This paper is an endeavor to picture excessive population threats to the resiliency of a large metropolitan area. By employing an existing evolutionary model of traffic flow on a small expository network, we show how chaotic situations occur at certain demand and supply parameter values and try to address the questions: How may one determine city population capacity for its transportation network, what happens if the city passes this limit, or how may one return the city to a stable situation when it runs into unstable or chaotic situations. Under certain assumptions, the paper designs a simulation experiment to revisit the phenomenon discovered by Greenshields in 1934, but for a... 

    Weak solutions to Vlasov-McKean equations under Lyapunov-type conditions

    , Article Stochastics and Dynamics ; Volume 19, Issue 6 , 2019 ; 02194937 (ISSN) Mehri, S ; Stannat, W ; Sharif University of Technology
    World Scientific Publishing Co. Pte Ltd  2019
    We present a Lyapunov-type approach to the problem of existence and uniqueness of general law-dependent stochastic differential equations. In the existing literature, most results concerning existence and uniqueness are obtained under regularity assumptions of the coefficients with respect to the Wasserstein distance. Some existence and uniqueness results for irregular coefficients have been obtained by considering the total variation distance. Here, we extend this approach to the control of the solution in some weighted total variation distance, that allows us now to derive a rather general weak uniqueness result, merely assuming measurability and certain integrability on the drift... 

    A non-homogeneous Hill's equation

    , Article Applied Mathematics and Computation ; Volume 167, Issue 1 , 2005 , Pages 68-75 ; 00963003 (ISSN) Shadman, D ; Mehri, B ; Sharif University of Technology
    The existence of periodic solutions for a forced Hill's equation is proved. The proof is then extended to the case of a non-homogeneous matrix valued Hill's equation. Under the stated conditions, using Lyapunov's criteria [Proc. AMS 13 (1962) 601; Hill's Equation, Interscience Publishers, New York, 1966] some results on the stability oh Hill's equation are obtained. © 2004 Elsevier Inc. All rights reserved  

    Adaptive boundary control of the size-dependent behavior of euler-bernoulli micro-beams with unknown parameters and varying disturbance

    , Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 231, Issue 10 , 2017 , Pages 1777-1790 ; 09544062 (ISSN) Nojoumian, M. A ; Vatankhah, R ; Salarieh, H ; Sharif University of Technology
    In this paper, modeling and vibration control of a strain-gradient clamped-free Euler-Bernoulli micro-beam exposed to varying disturbance is studied. A strain-gradient model of the Euler-Bernoulli micro-beam is represented in this paper and consisted of one partial differential equation and six ordinary equations as governing motion equation and boundary conditions, respectively. A boundary controller is proposed to suppress the system's vibration. The controller is derived based on the direct Lyapunov method. An adaptation law is devised to assure system's stability under parametric uncertainties. With the proposed adaptive robust boundary control, uniform boundedness under environmental... 

    Robust adaptive backstepping control of uncertain lorenz system [electronic resource]

    , Article Journal of American Institute of Physics ; 2010, Vol. 20, pp. 1-5 Nejat Pishkenari, H. (Hossein) ; Jalili, Nader ; Mahboobi, Seyed Hanif ; Alasty, Aria ; Meghdari, Ali ; Sharif University of Technology
    In this paper, a novel robust adaptive control method is proposed for controlling the Lorenz chaotic attractor. A new backstepping controller for the Lorenz system based on the Lyapunov stability theorem is proposed to overcome the singularity problem that appeared in using the typical backstepping control method. By exploiting the property of the system, the resulting controller is shown to be singularity free and the closed loop system is globally stable. Due to unavailability of system states measurement in practice, the controller is selected such that only one system state is needed. To overcome the problem of parameter uncertainty, an additional term to Lyapunov function is added and... 

    Synchronizing different chaotic systems using active sliding mode control

    , Article Chaos, Solitons and Fractals ; Volume 31, Issue 1 , 2007 , Pages 119-129 ; 09600779 (ISSN) Haeri, M ; Emadzadeh, A. A ; Sharif University of Technology
    An active sliding mode controller is designed to synchronize three pairs of different chaotic systems (Lorenz-Chen, Chen-Lü, and Lü-Lorenz) in drive-response structure. It is assumed that the system parameters are known. The closed loop error dynamics depend on the linear part of the response systems and parameters of the controller. Therefore, the synchronization rate can be adjusted through these parameters. Analysis of the stability for the proposed method is derived based on the Lyapunov stability theorem. Finally, numerical results are presented to show the effectiveness of the proposed control technique. © 2005 Elsevier Ltd. All rights reserved  

    Robust decentralized position/force control of cooperative robots without velocity measurement

    , Article 2005 IEEE International Conference on Industrial Technology, ICIT 2005, Hong Kong, 14 December 2005 through 17 December 2005 ; Volume 2005 , 2005 , Pages 1403-1408 ; 0780394844 (ISBN); 9780780394841 (ISBN) Sadati, N ; Elhamifar, E ; Sharif University of Technology
    A decentralized control scheme for multiple cooperative manipulators system is developed to achieve the desired performance in motion and force tracking in the presence of uncertainties in the dynamic equations of the robots. To reduce the effects of uncertainties in the closed-loop performance, a robust control algorithm using a robustifying term is proposed. Based on the Lyapunov stability method, it is proved that all the signals in the closed-loop, composed of a robot, an observer and a controller are uniformly ultimately bounded. Also to avoid the difficulties of using velocity sensors within the hand architecture an output feedback control scheme with a linear observer is used. © 2005... 

    Cryptanalysis of SIMON variants with connections

    , Article Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) ; Volume 8651 , 2014 , Pages 90-107 ; ISSN: 03029743 ; ISBN: 9783319130651 Alizadeh, J ; Alkhzaimi, H. A ; Aref, M. R ; Bagheri, N ; Gauravaram, P ; Kumar, A ; Lauridsen, M. M ; Sanadhya, S. K ; Sharif University of Technology
    SIMON is a family of 10 lightweight block ciphers published by Beaulieu et al. from the United States National Security Agency (NSA). A cipher in this family with K-bit key and N-bit block is called SIMONN/K. We present several linear characteristics for reduced-round SIMON32/64 that can be used for a key-recovery attack and extend them further to attack other variants of SIMON. Moreover, we provide results of key recovery analysis using several impossible differential characteristics starting from 14 out of 32 rounds for SIMON32/64 to 22 out of 72 rounds for SIMON128/256. In some cases the presented observations do not directly yield an attack, but provide a basis for further analysis for... 

    Impossible differential cryptanalysis of Piccolo lightweight block cipher

    , Article 2014 11th International ISC Conference on Information Security and Cryptology, ISCISC 2014 ; Sep , 2014 , p. 89-94 Azimi, S. A ; Ahmadian, Z ; Mohajeri, J ; Aref, M. R ; Sharif University of Technology
    This paper analyzes the Piccolo family of lightweight block ciphers against the impossible differential cryptanalysis. A combination of some ploys such as decreasing the S-box computations, finding an appropriate propagation of differentials, utilizing hash tables and using the linearity of the key-schedule as well as disregarding subkeys of two rounds lead to 12-round and 13-round impossible differential attack on Piccolo-80 and 15-round attack on Piccolo-128. The time and data complexity of the attack against Piccolo-80 is 255.18 and 236.34 for 12-round and 269.7 and 243.25 for 13-round, respectively. Moreover, the time and data complexity for 15 rounds cryptanalysis of Piccolo-128 are... 

    Related-key impossible differential cryptanalysis of full-round HIGHT

    , Article ICETE 2013 - 10th International Joint Conference on E-Business and Telecommunications; SECRYPT 2013 - 10th International Conference on Security and Cryptography, Proceedings, Reykjavik ; 2013 , Pages: 537-542 ; 9789898565730 (ISBN) Rostami, S ; Chafjiri, S. B ; Tabatabaei, S. A. H ; Sharif University of Technology
    The HIGHT algorithm is a 64-bit block cipher with 128-bit key length, at CHES'06 as a lightweight cryptographic algorithm. In this paper, a new related-key impossible differential attack on the full-round algorithm is introduced. Our cryptanalysis requires time complexity of 2127.276 HIGHT evaluations which is slightly faster than exhaustive search attack. This is the first related-key impossible differential cryptanalysis on the full-round HIGHT block cipher. Copyright  

    Recursive linear and differential cryptanalysis of ultralightweight authentication protocols

    , Article IEEE Transactions on Information Forensics and Security ; Volume 8, Issue 7 , 2013 , Pages 1140-1151 ; 15566013 (ISSN) Ahmadian, Z ; Salmasizadeh, M ; Aref, M. R ; Sharif University of Technology
    Privacy is faced with serious challenges in the ubiquitous computing world. In order to handle this problem, some researchers in recent years have focused on design and analysis of privacy-friendly ultralightweight authentication protocols. Although the majority of these schemes have been broken to a greater or lesser extent, most of these attacks are based on ad-hoc methods that are not extensible to a large class of ultralightweight protocols. So this research area still suffers from the lack of structured cryptanalysis and evaluation methods. In this paper, we introduce new frameworks for full disclosure attacks on ultralightweight authentication protocols based on new concepts of... 

    Observations on the dynamics of bubble cluster in an ultrasonic field

    , Article Nonlinear Dynamics ; Volume 72, Issue 3 , 2013 , Pages 561-574 ; 0924090X (ISSN) Behnia, S ; Zahir, H ; Yahyavi, M ; Barzegar, A ; Mobadersani, F ; Sharif University of Technology
    The dynamics driven interaction between the bubbles in a cavitation cluster is known to be a complex phenomenon indicative of a highly active nonlinear as well as chaotic behavior in ultrasonic fields. By considering the cluster of encapsulated microbubble with a thin elastic shell in ultrasonic fields, in this paper, the dynamics of microbubbles has been studied via applying the methods of chaos physics. Bifurcation, Lyapunov exponent, and time series are plotted with respect to variables such as amplitude, initial bubble radius, frequency and viscosity. The findings of the study indicate that a bubble cluster undergoes a chaotic unstable region as the amplitude and frequency of ultrasonic... 

    Impossible differential cryptanalysis of reduced-round TEA and XTEA

    , Article 12th International ISC Conference on Information Security and Cryptology, 8 September 2015 through 10 September 2015 ; 2015 , Pages 58-63 ; 9781467376099 (ISBN) Hajari, M ; Azimi, S.A ; Aghdaie, P ; Salmasizadeh, M ; Aref, M. R ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc 
    TEA and XTEA are two lightweight Feistel block ciphers, each of which has a block size of 64 bits and a key size of 128 bits. These two ciphers have ARX structure, i.e. their round functions consist of modular addition, shift and XOR to be exact. Since each operation of TEA and XTEA can be done in a bitwise fashion, we are able to use early abort technique in the impossible differential attack that helps us to remove inappropriate pairs as soon as possible, hence decreasing time complexity. In this paper we present two new 15-round impossible differential characteristics, resulting in the first known impossible differential cryptanalysis mounted on 19 rounds of TEA and 25 rounds of XTEA  

    Chaos in the APFM nonlinear adaptive filter

    , Article Signal Processing ; Volume 89, Issue 5 , 2009 , Pages 697-702 ; 01651684 (ISSN) Tavazoei, M. S ; Haeri, M ; Sharif University of Technology
    In this paper, we show that an amplitude phase frequency model (APFM) which is used as a nonlinear adaptive filter in signal processing can exhibit chaotic behavior. It is illustrated that both frequency and amplitude of the input components have effect on the filter characteristics which can lead the filter to behave chaotically for some values of these parameters. We have exploited different measures such as the Lyapunov exponents, bifurcation diagram, sensitivity to initial condition, and 0-1 test on time series to confirm our claim. Existence of the chaotic behavior in APFM does not conform to the prior conjectures about this filter. © 2008 Elsevier B.V. All rights reserved  

    Adaptive fuzzy sliding mode control using multiple models approach

    , Article IEEE International Conference on Engineering of Intelligent Systems, ICEIS 2006, Islamabad, 22 April 2006 through 23 April 2006 ; 2006 ; 1424404568 (ISBN); 9781424404568 (ISBN) Sadati, N ; Ghadami, R ; Sharif University of Technology
    In this paper, an adaptive fuzzy sliding mode controller using multiple models approach is presented. By using the multiple models technique the nominal part of the control signal is constructed according to the most appropriate model at different environments. Adaptive single-input single-output (SISO) fuzzy system is used to approximate the discontinuous part of control signal; control gain, in a classical sliding mode controller. The key feature of this scheme is that prior knowledge of the system uncertainties is not required to guarantee the stability. Also the chattering phenomenon in sliding mode control is alleviated and steady tracking error is eliminated. Moreover, a theoretical... 

    Observer-based control design for three well-known chaotic systems

    , Article Chaos, Solitons and Fractals ; Volume 29, Issue 2 , 2006 , Pages 381-392 ; 09600779 (ISSN) Mahboobi, S. H ; Shahrokhi, M ; Pishkenari, H. N ; Sharif University of Technology
    In this paper, a singularity-free approach is proposed for controlling three well-known chaotic systems namely Lorenz, Chen and Lu. The control design guarantees the regulation of two states and boundedness of the remaining state. The stability of the proposed scheme has been shown using the Lyapunov stability theorem. Implementation of the proposed control technique requires system states, while in most of practical applications only the system output is available. To overcome this problem, a nonlinear observer is coupled with the controller. Simulation results have illustrated the effectiveness and robustness of the proposed schemes. If the control action is applied to the second system... 

    Chaotic dynamics of active topological defects

    , Article Soft Materials ; Volume 19, Issue 3 , 2021 , Pages 316-322 ; 1539445X (ISSN) Hashemi, A ; Ejtehadi, M. R ; Sharif University of Technology
    Taylor and Francis Ltd  2021
    Topological defects are interesting phenomena which can be observed in ordered phases such as oriented active fluids or nematic liquid crystals. Topological defects are determined by the overall structure of the director field in an active fluid in nematic phase and by exerting force to the units of the active particles they can interact or cause motion in the environment. Studying them as particles with dynamical equations, instead of studying the director field of the nematic environment, would provide us the power to study the characteristics of their motion. The equations of motion for multi-defect systems have been previously studied and in this work we focus on the chaotic properties... 

    Application of neural networks to decentralized control of robot manipulators with high degree of freedom

    , Article ICTAI 2005: 17th IEEE International Conference on Tools with Artificial Intelligence, ICTAI'05, Hong Kong, 14 November 2005 through 16 November 2005 ; Volume 2005 , 2005 , Pages 484-488 ; 10823409 (ISSN); 0769524885 (ISBN); 9780769524887 (ISBN) Sadati, N ; Elhamifar, E ; Sharif University of Technology
    In this paper a neural network decentralized control for trajectory tracking of robot manipulators is developed. The proposed decentralized control allows the overall closed-loop system to be stabilized while making the tracking error to be uniformly ultimately bounded (UUB), without having any prior knowledge of the robot manipulator dynamics. The interconnections in the dynamic equations of each subsystem are considered with unknown nonlinear bounds. The RBF neural networks (RBFNNs) are proposed to model the unknown nonlinear dynamics of the robots and the interconnection terms. Using Lyapunov method, the stability of the overall system is investigated, © 2005 IEEE  

    Design of a supervisory controller for CLOS guidance with lead angle

    , Article AIAA Guidance, Navigation, and Control Conference 2005, San Francisco, CA, 15 August 2005 through 18 August 2005 ; Volume 4 , 2005 , Pages 3083-3095 ; 1563477378 (ISBN); 9781563477379 (ISBN) Nobahari, H ; Alasty, A ; Pourtakdoust, S. H ; Sharif University of Technology
    This paper proposes a supervisory Command to Line-of-Sight (CLOS) guidance law with lead angle. The proposed scheme guarantees the missile to fly within the beam, when there is a beam angle constraint. In this regard a supervisory controller is coupled with a main Sliding Mode Controller (SMC). The supervisory control signal is activated when the beam constraint goes to be violated. First the supervisory controller is designed based on a recent idea on how the states of a nonlinear system with local stable controller can be controlled to stay within the domain of attraction. Then a sliding mode controller is designed, as the main tracking controller, to force the missile to fly along the...