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ELECTRONICS LETTERS 1998年第9期34卷 871-873页

作者： Knudsen, LR Preneel, B Univ Bergen Dept Informat N-5020 Bergen Norway Katholieke Univ Leuven Dept Elect Engn ESAT COSIC B-3001 Heverlee Belgium

A new message authentication code (mac) algorithm is proposed, which improves the popular retail mac based on the data encryption standard;it has the same complexity, but provides better resistance against key recovery attacks. Ln addition, a new key recovery attack on the retail mac is presented, requiring a single known text-mac pair and 2(56) online mac verifications.

关键词： message authentication message authentication code data encryption standard macDES standards Data security public key cryptography Codes DES online mac verifications mac algorithm single known text-mac pair key recovery attacks

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COMPUTATION OF FLOW PAST COMPLEX GEOMETRIES USING mac algorithm ON BODY-FITTED COORDINATES

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ENGINEERING APPLICATIONS OF COMPUTATIONAL FLUID MECHANICS 2009年第1期3卷 15-27页

作者： Patil, Pratish P. Tiwari, Shaligram Indian Inst Technol Dept Mech Engn Madras 600036 Tamil Nadu India

The study aims to report an algorithm based on co-ordinate transformation to compute complex flows. A two-dimensional computational code is developed using transformation of governing incompressible flow equations by employing body-fitted co-ordinates. The complex flows may involve external flows past obstacles having curved surfaces or internal flows confined in curved domains. The transformed governing equations are discretized using mac algorithm. The code has been validated by comparing variation of Strouhal number with Reynolds number for flow past a circular cylinder.

关键词： complex geometries body-fitted co-ordinates mac algorithm incompressible flows skewed grids

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A novel broadcasting mac algorithm for ad hoc networks 8th

A novel broadcasting MAC algorithm for ad hoc networks

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8th International Conference on Advances in Information Technology (IAIT)

作者： Liang, Chen Zhang, Yu Song, Jian Tsinghua Univ Dept Elect Engn Tsinghua Natl Lab Informat Sci & Technol TNList Beijing 100084 Peoples R China Sci & Technol Informat Transmiss & Disseminat Com Shenzhen 518057 Peoples R China Shenzhen City Key Lab Digital TV Syst Shenzhen 518057 Peoples R China

Wireless ad hoc networks with broadcasting are widely applied in IoT and emergency situations as the network can be set up without traditional infrastructures. In this paper, we propose a TDMA-based mac algorithm which supports data transmission by broadcasting. The algorithm is similar with the mechanism in NbIA algorithm (1,2) in neighbour discovery, but differs a lot in collision detection and slot allocation. Our algorithm can dynamically allocate slots according to the demand of nodes and ensures every node get at least one slot a cycle. Based on spatial reuse, idle slots might be found and be used as extra slots of nodes which can promote throughput of our algorithm. After the network converges, only a few nodes need to adjust their slots to adapt to topology changes, while most of the nodes maintain their slots to transmit data. The performance of our algorithm and NbIA algorithm are compared with OPNET simulation. The results show that our algorithm outperforms NbIA especially in convergence time and average throughput of nodes. (C) 2017 The Authors. Published by Elsevier B.V.

关键词： Ad hoc network mac algorithm Broadcast Slot assignment

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A novel broadcasting mac algorithm for ad hoc networks

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Procedia Computer Science 2017年 111卷 268-276页

作者： Chen Liang Yu Zhang Jian Song Tsinghua National Laboratory for Information Science and Technology (TNList) Tsinghua University Department of Electronics Engineering Tsinghua University Beijing 100084 China Science and Technology on Information Transmission and Dissemination in Communication Networks Laboratory Shenzhen City Key Laboratory of Digital TV System Shenzhen 518057 China

Wireless ad hoc networks with broadcasting are widely applied in IoT and emergency situations as the network can be set up without traditional infrastructures. In this paper, we propose a TDMA-based mac algorithm which supports data transmission by broadcasting. The algorithm is similar with the mechanism in NbIA algorithm 1,2 in neighbour discovery, but differs a lot in collision detection and slot allocation. Our algorithm can dynamically allocate slots according to the demand of nodes and ensures every node get at least one slot a cycle. Based on spatial reuse, idle slots might be found and be used as extra slots of nodes which can promote throughput of our algorithm. After the network converges, only a few nodes need to adjust their slots to adapt to topology changes, while most of the nodes maintain their slots to transmit data. The performance of our algorithm and NbIA algorithm are compared with OPNET simulation. The results show that our algorithm outperforms NbIA especially in convergence time and average throughput of nodes.

关键词： Ad hoc network mac algorithm Broadcast Slot assignment

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mac versus PC: Determinism and randomness as complementary approaches to robotic exploration of continuous unknown domains

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INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH 2000年第1期19卷 12-31页

作者： Wagner, IA Lindenbaum, M Bruckstein, AM IBM Haifa Res Lab IL-31905 Haifa Israel Technion Israel Inst Technol Dept Comp Sci IL-32000 Haifa Israel

Three methods are described for exploring a continuous unknown planar region by a group of robots having limited sensors and no explicit communication. We formalize the problem, prove that its off-line version is NP-hard, and show a lower bound on the length of any solution. Then a deterministic mark and cover (mac) algorithm is described for the on-line problem using short-lived navigational markers as a means of navigation and indirect communication. The convergence of the algorithm is proved, and its cover time is shown, to be the asymptotically optimal O(A/a), where A is the total area and a is the area covered by the robot in a single step. The mac algorithm is tested against an alternative randomized probabilistic covering (PC) method which does not rely on sensors but is still able to cover an unknown region in an expected time that depends polynomially on the dimensions of the region. Both, algorithms enable cooperation of several robots to achieve faster coverage. Finally, we show that the two methods can be combined to yield a third, hybrid algorithm with a better trade-off between performance and robustness.

关键词： Determinism Exploration Unknown mac algorithm algorithms Random Number Generators Sensors Nondeterministic polynomial-time hard navigation Robot Fate Media Access Protocol

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A Real Time Testbed for the Evaluation of Cognitive Radio mac

A Real Time Testbed for the Evaluation of Cognitive Radio MA...

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IEEE Global Telecommunications Conference (GLOBECOM 2010)

作者： Gu, Shen Xu, Pengchao Wang, Xinbing Gan, Xiaoying Yu, Hui Shanghai Jiao Tong Univ Dept Elect Engn Shanghai Peoples R China

ISBN: (纸本)9781424456383

Cognitive Radio is a promising technology to solve the problem of increasing spectrum shortage in wireless communication. It allows secondary users(SUs) to opportunistically access idle spectrum of primary users(PUs) while ensuring collision perceived by PUs under a specific requirement. Testbed is essential to advance the development of cognitive radio networks. This paper presents a real time testbed for the evaluation of the cognitive radio mac algorithm. The testbed supports the necessary components of cognitive radio including programmable RF transceiver, software-defined mac layer and adaptive network layer to support multi-PU multi-SU cognitive radio networks. It is much easier to configure and control than the traditional FPGA-based testbed by using system-on-chip(SoC) programmable processors. We present the main features and the implementation details of the testbed in this paper. We also introduce an experiment using the testbed to evaluate the performance of an adaptive CR mac algorithm proposed by us.

关键词： FPGA mac algorithm access protocols cognitive radio cognitive radio field programmable gate arrays programmable RF transceiver programmable processors radio transceivers real time testbed software defined radio software radio system-on-chip system-on-chip

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Three-dimensional numerical investigations on flow and heat transfer for flow past a channel confined square cylinder

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PROGRESS IN COMPUTATIONAL FLUID DYNAMICS 2010年第3期10卷 146-156页

作者： Patil, Pratish P. Tiwari, Shaligram Indian Inst Technol Madras Dept Mech Engn Chennai 600036 Tamil Nadu India

Present work investigates three-dimensional fluid flow and heat transfer for flow past a square cylinder built-in a rectangular channel. The governing equations for viscous fluid flow and heat transfer are solved numerically with the help of an indigenously developed computational code based on modified mac algorithm. Unsteady computations are performed for Reynolds number in the range of 400-1000 and channel height ranging from 0.5d to 3d (d being side of the square cylinder). The effect of channel height on onset of vortex shedding, other flow characteristics and heat transfer from heated solid surfaces has been presented.

关键词： fluid flow and heat transfer mac algorithm square cylinder channel-confinement Nusselt number Strouhal number limiting streamlines

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A Decentralized Lightweight Authentication and Privacy Protocol for Vehicular Networks

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IEEE ACCESS 2019年 7卷 119689-119705页

作者： Hakeem, Shimaa A. Abdel Abd El-Gawad, Mohamed A. Kim, Hyungwon Chungbuk Natl Univ Elect Engn Dept Cheongju 28644 South Korea ERI Giza 12622 Egypt Natl Telecommun Inst Cairo 11768 Egypt

Recently many security protocols have been proposed for road safety applications in Vehicle-to-everything (V2X) communications. Most of them, however, do not fully satisfy the requirements of light-weight and fast processing, which are special properties for V2X. Most of the previous authentication protocols assume that a Certificate Authority (CA) is present within the communication range from all the vehicles, which is not practical for moving vehicles. We propose a light-weight security protocol for authentication and privacy protection for V2X. It employs two security hardware devices, Biometric Device (BD) and Tamper Proof Device (TPD), which verifies the driver and securely keeps the keys, respectively. It decentralizes the CA's tasks by locally generating pseudo-identity and private keys to preserve privacy and provide authentication in Vehicle-to-Vehicle (V2V) communication. In addition, we propose an authentication signature protocol using a notion of hash-chain key generation. We implemented the proposed key generation and authentication protocol using NS-3 simulator. Our extensive simulations demonstrated that the proposed authentication protocol significantly enhances the security level while protecting the conditional privacy of vehicles by utilizing anonymous identities. The proposed protocol has a 20% similar to 85% less communication overhead compared with the previous protocols.

关键词： Hash-chain mac algorithm privacy two-factor authentication biometric tamperproof

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NUMERICAL STUDY OF FREE CONVECTION Ag-WATER NANOFLUID FLOW IN A SQUARE ENCLOSURE WITH VISCOUS DISSIPATION AND HEAT GENERATION/ABSORPTION EFFECTS IN A POROUS MEDIUM WITH COMPLEX WALL CONDITIONS

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JOURNAL OF POROUS MEDIA 2023年第9期26卷 77-99页

作者： Vinodhini, Nithiyanandam Prasad, Vallampati Ramachandra Vellore Inst Technol Sch Adv Sci Dept Math Vellore 632014 India

Nanofluids hold great promise in improving transport processes in energy systems including hybrid fuel cells. In this present work, a mathematical model is developed for laminar free convection flow of Ag-water nano-additives in an enclosure in a porous medium with complex boundary conditions. Additionally, heat generation/absorption and viscous dissipation effects are included. Via appropriate scaling transformations, the conservation equations for mass, primary and secondary momentum, energy, and nanoparticle vorticity with wall boundary conditions are rendered dimensionless. A finite-difference computational scheme known as the marker and cell (mac) method, developed by Harlow and Welch, is occupied to solve the dimensionless, nonlinear coupled boundary value problem. A mesh independence study is included. The impact of parameters such as Eckert number (Ec), Darcy number (Da), Grashof number (Gr), Prandtl number (Pr), Reynolds number (Re), and Richardson number (Ri) are observed with physical framework. Graphical plots are presented for the impact of key control parameters on streamline contours, isotherm contours, and local Nusselt number. By heat sink (absorption), the Nusselt number is increased, whereas by heat generation it is reduced since there is a decrease in heat transferred to the boundary. The presence of viscous dissipation effects moves the streamlines toward the blue core and allows the temperature to increase in the neighborhood of the hot wall of the envelope. An increase in Richardson number induces a flip in vortex cell structures from an initially strong circulation cell on the left and weaker cell on the right, to the opposite distribution. Significant cooling is also induced in the core zone with an increasing Richardson number, and a decrease in vorticity is observed.

关键词： convective flow Ag-water nanoparticles isotropic porous medium mac algorithm square enclosure viscous dissipation

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Comparative Experiments of V2X Security Protocol Based on Hash Chain Cryptography

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SENSORS 2020年第19期20卷 5719.-5719.页

作者： Hakeem, Shimaa A. Abdel Abd El-Gawad, Mohamed A. Kim, HyungWon Chungbuk Natl Univ Sch Elect Engn Cheongju 28644 South Korea Elect Res Inst ERI Giza 12622 Egypt Korea Univ Sch Elect Engn Seoul 02841 South Korea Natl Telecommun Inst Cairo 11768 Egypt

Vehicle-to-everything (V2X) is the communication technology designed to support road safety for drivers and autonomous driving. The light-weight security solution is crucial to meet the real-time needs of on-board V2X applications. However, most of the recently proposed V2X security protocols-based on the Elliptic Curve Digital Signature algorithm (ECDSA)-are not efficient enough to support fast processing and reduce the communication overhead between vehicles. ECDSA provides a high-security level at the cost of excessive communication and computation overhead, which motivates us to propose a light-weight message authentication and privacy preservation protocol for V2X communications. The proposed protocol achieves highly secure message authentication at a substantially lower cost by introducing a hash chain of secret keys for a Message Authentication Code (mac). We implemented the proposed protocol using commercial V2X devices to prove its performance advantages over the standard and non-standard protocols. We constructed real V2X networks using commercial V2X devices that run our implemented protocol. Our extensive experiments with real networks demonstrate that the proposed protocol reduces the communication overhead by 6 times and computation overhead by more than 100 times compared with the IEEE1609.2 standard. Moreover, the proposed protocol reduces the communication overhead by 4 times and the computation overhead by up to 100 times compared with a non-standard security protocol, TESLA. The proposed protocol substantially reduces the average end-to-end delay to 2.5 ms, which is a 24- and 28-fold reduction, respectively, compared with the IEEE1609 and TESLA protocols.

关键词： mac algorithm hash-chain privacy commercial V2X devices authentication IEEE1609 2

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